What Are the Main Types of Holograms Today

What Are the Main Types of Holograms Today?By Dr. Tung. H. Jeong

Copyright © 2005 Integraf LLC

1. INTRODUCTION

A hologram is a recording in a two- or three-dimensional medium of the interference pattern formed when a point source of light (the reference beam) of fixed wavelength encounters light of the same fixed wavelength arriving from an object (the object beam). When the hologram is illuminated by the reference beam alone, the diffraction pattern recreates the wave fronts of light from the original object. Thus, the viewer sees an image indistinguishable from the original object.

There are many types of holograms, and there are varying ways of classifying them. For our purpose, we can divide them into two types: reflection holograms and transmission holograms.

2. THE REFLECTION HOLOGRAM

The reflection hologram, in which a truly three-dimensional image is seen near its surface, is the most common type shown in galleries. The hologram is illuminated by a “spot” of white incandescent light, held at a specific angle and distance and located on the viewer’s side of the hologram. Thus, the image consists of light reflected by the hologram. Recently, these holograms have been made and displayed in color—their images optically indistinguishable from the original objects. If a mirror is the object, the holographic image of the mirror reflects white light; if a diamond is the object, the holographic image of the diamond is seen to “sparkle.”

Although mass-produced holograms such as the eagle on the VISA card are viewed with reflected light, they are actually transmission holograms “mirrorized” with a layer of aluminum on the back.

3. THE TRANSMISSION HOLOGRAM

The typical transmission hologram is viewed with laser light, usually of the same type used to make the recording. This light is directed from behind the hologram and the image is transmitted to the observer’s side. The virtual image can be very sharp and deep. For example, through a small hologram, a full-size room with people in it can be seen as if the hologram were a window. If this hologram is broken into small pieces (to be less wasteful, the hologram can be covered by a piece of paper with a hole in it), one can still see the entire scene through each piece. Depending on the location of the piece (hole), a different perspective is observed. Furthermore, if an undiverged laser beam is directed backward (relative to the direction of the reference beam) through the hologram, a real image can be projected onto a screen located at the original position of the object.

3. HYBRID HOLOGRAMS

Between the reflection and transmission types of holograms, many variations can be made.

Embossed holograms: To mass produce cheap holograms for security application such as the eagle on VISA cards, a two-dimensional interference pattern is pressed onto thin plastic foils.

The original hologram is usually recorded on a photosensitive material called photoresist. When developed, the hologram consists of grooves on the surface. A layer of nickel is deposited on this hologram and then peeled off, resulting in a metallic “shim.” More secondary shims can be produced from the first one. The shim is placed on a roller. Under high temperature and pressure, the shim presses (embosses) the hologramonto a roll of composite material similar to Mylar.

Integral holograms: A transmission or reflection hologram can be made from a series of photographs (usually transparencies) of an object—which can be a live person, an outdoor scene, a computer graphic, or an X-ray picture. Usually, the object is “scanned” by a camera, thus recording many discrete views. Each view is shown on an LCD screen illuminated with laser light and is used as the object beam to record a hologram on a narrow vertical strip of holographic plate (holoplate). The next view is similarly recorded on an adjacent strip, until all the views are recorded. When viewing the finished composite hologram, the left and right eyes see images from different narrow holograms; thus, a stereoscopic image is observed. Recently, video cameras have been used for the original recording, which allows images to be manipulated through the use of computer software.

Holographic interferometry: Microscopic changes on an object can be quantitatively measured by making two exposures on a changing object. The two images interfere with each other and fringes can be seen on the object that reveal the vector displacement. In real-time holographic interferometry, the virtual image of the object is compared directly with the real object. Even invisible objects, such as heat or shock waves, can be rendered visible. There are countless engineering applications in this field of holometry.

Multichannel holograms: With changes in the angle of the viewing light on the same hologram, completely different scenes can be observed. This concept has enormous potential for massive computer memories.

Computer-generated holograms: The mathematics of holography is now well understood. Essentially, there are three basic elements in holography: the light source, the hologram, and the image. If any two of the elements are predetermined, the third can be computed. For example, if we know that we have a parallel beam of light of certain wavelength and we have a “double-slit” system (a simple “hologram”), we can calculate the diffraction pattern. Also, knowing the diffraction pattern and the details of the double-slit system, we can calculate the wavelength of the light. Therefore, we can dream up any pattern wewant to see. After we decide what wavelength we will use for observation, the hologram can be designed by a computer. This computer-generated holography (CGH) has become a sub-branch that is growing rapidly. For example, CGH is used to make holographic optical elements (HOE) for scanning, splitting, focusing, and, in general, controlling laser light in many optical devices such as a common CD player.

Read more:http://www.integraf.com/a-Types_of_Holograms.htm#ixzz1ldbnVxML

HOLOGRAPHY KIT CONTENTS

Step-by-Step Instructions

PFG-03M professional holographic plates, 2.5”x2.5” (63mm x 63mm), 30 plates**

JD-4 Holography Processing Kit**

PhotoFlo wetting agent (30ml)

Holography diode laser with battery holder

Clothespin

Three reusable plastic developer trays

HOLOGRAPHY by Dr. Tung H. Jeong (pamphlet)

Laser Holography—Experiments You Can Do by Dr. Tung H. Jeong (booklet)

** May generally be substituted with a PFG-01 and JD-2 combination.

NOTICE

Open your unexposed holographic plates only in the dark or under appropriate darkroom lighting. Read the Terms and Conditions of Use in this packet, and all instructions and safety notices for the laser and chemicals before starting.

REQUIREMENTS AND OTHER MATERIALS

The following can be found in most homes or purchased very economically at your local drug or general store.

Requirements

A room that is dark when lights are off, and has minimal noise and vibration (creaky floors, etc.)

A stable table (to serve as your work area)

A bright hard object, preferably sturdy metal, i.e. coins (to be the subject of your hologram)

Two “D” size batteries (to power the laser)

One flat hardcover book 6”x8” (150x200mm) or larger (to serve as a shutter).

A small cup filled with sand (to hold the laser)—salt or sugar also works

A vase or any solid object about 1 foot (30cm) high (to serve as a tower upon which to place the laser).Six 1-liter bottles (1.5 gallons) of distilled water (to prepare the processing chemicals)

Two large trays (or bowls) with flat bottoms 4”x5” or preferably larger (to serve as rinse water trays)

One rubber kitchen glove or tongs (to handle the holographic plate while developing)

Optional

A basic nightlight available at your supermarket or green safelight (to conveniently see in the dark room)A computer mouse pad or a tray of sand (or salt or sugar) with width, length, and height of very roughly 6”x8”x2” (15x20x5cm) or larger (to serve as a vibration isolation system)

ADDITIONAL RESOURCES

Recommended Reading

Visit our dedicated online resources for your holography kit at http://www.integraf.com/hk.htm. There you can find additional tips and ideas about how to make holograms. We recommend reading our online article “Simple Holography”, the ideas of which inspired the creation of this holography kit and process.

Holography Helpline

At Integraf, our mission is to help you and your students make holograms. So, don’t be shy about contacting us via email or phone if you seek technical advice. Our technical support is led by Dr. Tung H. Jeong, a world-expert in holography and education with over 35 years experience.

We recommend you try making a couple of holograms first before contacting us. This way we can provide the accurate and focused feedback to your questions. Describe your set up, what you’ve tried, and what you are seeing. Also take a look at our “Trouble Shooting” section found at the back of this instruction packet.

Feedback

Thank you for purchasing the Integraf holography kit. We strive to provide the best products and services to our customers, and kindly invite you to email us with your comments.

TERMS AND CONDITIONS OF USE

By purchasing, accepting, or using products from Integraf, you recognize that these products are intended for hologram making and education, and that reasonable care, caution, and adult supervision should be exercised in their intended use and such use only. You also agree to assume all risks of using, handling, storing, and disposal of any products, including but not limited to the Chemical Products and Laser Products described herein (“products”). If you for any reason do not want to or cannot assume all risks, please call (650) 351-5003 to return your product for a full refund.

Chemical Products. Some of our products contain chemicals, including but not limited to JD 2, JD-3, JD 4, and PhotoFlo (“dark room items”). Like many common household cleaners, each dark room item may contain small amounts of chemicals considered hazardous by the EPA, and should thus be treated with respect. You should read all safety labels and instructions prior to use. While the solutions made with dark room items have lower volatility than many household cleaners, working in a ventilated area is recommended. It is also good practice to wear aprons, dusk mast, safety goggles, and gloves when handling chemicals. Keep dark room items and their solutions away from children and food, and clearly mark them as not to be ingested. A responsible adult should supervise the use, handling, storage, and disposal of any dark room items and their solutions by minors. Copies of the material safety data sheets (MSDS) for all dark

room items may be viewed and downloaded from our website at http://www.integraf.com, and are also available upon request.

Laser Products. The holography laser diode (“laser”) provided by Integraf is classified as Class IIIa, meaning it may be safe for momentary viewing but is a recognized eye hazard if viewed through optics (telescopes, magnifiers). Avoid looking directly into the laser light. Keep from the reach of from infants since the laser is small and may be a choking hazard.

Other Considerations. Always carefully handle glass plates, holographic or otherwise, as there is always the possibility that areas of these products may be sharp. As with all science experimentation, one should always practice reasonable and safe laboratory procedures and practices, especially since much of hologram making will happen in a darkened room.

Products are for laboratory use and use under adult supervision at home only, and are not for human ingestion, consumption, or other application. By accepting or using these products, you agree to assume all risk for use or keeping of such products, and you agree to exempt and release Integraf and any of its directors, officers, employees, agents, advisors, suppliers, and manufacturers from any and all liability, claims, expenses (including legal fees, medical expenses, or otherwise), demands or actions or causes of action whatsoever arising out of any damage, loss, injury, pain, suffering, or death as a result of their use. This release encompasses all losses, damages, expenses, injuries and pain, physical or mental, and deaths resulting from any cause, whether the fault of the user, a defect in the product, or misuse regardless of intention. This product liability limitation cannot be amended, altered or made void by any representative either verbally or in writing of Integraf, supplier, or the manufacturer, and the consumer agrees to the terms of these limitations when purchasing or receiving merchandise from Integraf. If you do not agree to these terms, please return the products for a full refund.

STEP-BY-STEP INSTRUCTIONS

The “white light reflection hologram” is one of the simplest hologram to make. We recommend you thoroughly read all instructions and tips here first before starting. You might even try a “practice run” without using any holographic plate first, as a way to familiarize yourself with the process.

1. Define your laboratory space. Choose a sturdy table in a dark room that is free of noise, vibration, air currents, and small movements (creaky floors, etc.). In the same room or in another dark room, find a place to set up as your chemical processing room (well ventilated, preferably near a sink, etc.).

2. Gather holography kit contents and the additional household materials listed above

3. Prepare the subject and your optional vibration isolation system. Place the subject securely on the sturdy table. If you have a computer mouse pad or tray of sand, place the subject on top of that. For your first hologram, we highly recommend using bright coins, e.g. quarters, dimes, nickels. By learning from your first successful hologram, you be able to venture onto using other subjects more easily.

4. Prepare and warm up the laser diode for at least 5 minutes

a. Unscrew the black collimating lens and spring off your laser, and store them away.

b. Clip the metal cylindrical area of your diode laser with the clothespin.

c. Stick the other end of the clothespin securely into the cup of sand.

d. Load the battery pack with two D-size batteries and then connect the wires together (red to red, black to black) to power the laser.

e. Position laser so that its beam spreads out horizontally in an elliptical shape (it looks similar to that of a loaf of bread).

5. Position the laser until the subject is optimally and fully illuminated.

a. Place the vase serving as your tower up-side-down about 1 foot (30cm) away from the subject. You can substitute the vase with any other sturdy object of similar height (stack bricks, a wooden box, lab stand, etc.). Avoid books, cardboard or anything else that may deform.

b. Place your cup with laser on top of the tower, and angle the laser down toward the object. Lean the clothespin along the edge of the cup so it is braced against movement.

c. Adjust laser angle until the subject area is fully illuminated. (You may need to dim the lights to see this).

6. Prepare the chemical solutions following the instructions found in your JD holography processing kit.

7. Turn off all lights except your green safelight if you are using one. If you’re using a standard night light, position it under table or behind something so the light does not directly shine anywhere near your work area. If you have neither, simply allow a tiny amount of soft light to sneak indirectly through the crack under the door to your room. Block any direct light from reaching the holography system. The room should be dark enough that one cannot read.

8. Completely block the laser light from reaching the subject with one book. The book will serve like a shutter in a camera.

9. Prepare one holographic plate

a. Remove one plate from its box in the darkest part of the room.

b. Make sure all remaining unexposed plates are safely placed back into the original box to protect them from unintended exposure.

c. Identify which side of the plate has the holographic emulsion. It feels slightly sticky side when touched with moistened fingers. (If you cannot identify it, don’t worry, the hologram will still work.)

10. Carefully place the plate on top of the subject (coins), ideally with the emulsion side facing down against the subject. Though not required, it is helpful to remember which side you leaned toward the object since you’ll need to know this later for viewing the hologram later.

11. Make the hologram exposure

a. Allow at least 10 seconds for the subject and holographic plate to settle. Hold still and maintain absolute silence.

b. Now, slowly lift the “shutter” slightly off the table a half inch (1cm) while still blocking the laser light from reaching any part of the plate, and wait a few seconds for any vibration to subside.

c. Then, lift the shutter all the way up to expose the holographic plate and object for about 10 seconds.

d. Then, block the laser light by placing the book back on the table.

12. Process the plate according to instructions that accompany your JD holography processing kit.

13. Dry the holographic plate vertically. A simple way to do this is by placing the plate on a paper towel and lean it against a wall. If time is limited, you can carefully blow warm air across the holographic plate using a hair dryer from at least foot (30cm) away. Avoid high heat.

After the hologram is thoroughly dried, your reflection hologram can be viewed with a point source of incandescent light such as that from a projector, flashlight, spotlight, LED white light, or the sun. Shine the spotlight from the same angle your laser beam shined on the plate during exposure. One cannot use diffused light sources such as frosted bulbs and florescent lamps. Note that though the plate may look dry, it sometimes still has moisture on it.

TIPS & TOPICS TO HELP YOU MAKE HOLOGRAMS

1.0 Avoid Vibration

Vibration and minute movements are the main reason holograms don’t turn out. If any part of your holography system moves even one millionth of meter during exposure, your hologram will not likely turn out. So avoid talking, music, noise, walking around, air currents, creaky floors, soft objects, temperature changes to the object. . . . What other things can you think of that might cause vibration?

Many items deform beyond what we can see with the naked eye. This is due to tension, gravity, changes in temperature, and air current, among other things. Avoid using items made of soft plastic, paper, and cardboard when choosing your subject and other parts of your system.

If one is using holographic film instead of plates, know that film is particularly vulnerable to discreet movements and vibration. The film can flutter under air current or shrink and expand due to the heat on your fingers. To address this, we sandwich the film between two glass plates fastened by clips, squeeze out any air pockets between the film and the glass plates, and let the film-plate sandwich settle for a full five minutes.

Given the above, it is understandable why we should find a work area with a sturdy table that is far from noise and vibration (air conditioners, heating vents, noisy traffic outside, etc.). Using a computer mouse pad or tray of sand (or salt or sugar) helps dampen vibration.

2.0 Choose Your Subject Wisely

For the subject of your first hologram, we recommend using coins, such as quarters or dimes, since these are bright, hard, and non-deforming. By successfully making one hologram first, you will learn the fundamentals needed to venture onto using other objects.

For your subsequent holograms, the appropriate choice of your subject is critical. In general, your subject should ideally (1) be made of a solid material such metal or porcelain; (2) appear bright when illuminated with the red laser light; and (3) not move or deform.

Try to avoid choosing objects that are fabric or furry objects (e.g. teddy bear), since these objects deform most easily. Try to also avoid large plastic objects as they tend to expand and contract with the slightest change in temperature (even from the heat of your fingers!).

3.0 Prepare the Diode Laser for Holography

To make holograms, unscrew the black collimating lens from the front of the laser. A small spring behind the lens will pop out. Keep both in a safe place so you can put them back on later (this protects the laser from dirt and dust for future use). Hold the laser by the brass cylinder and avoid touching the exposed circuit board. By removing lens, the beam can shine out much like a flashlight and illuminate an elongated elliptical area.

To power the laser, use two D-size batteries (3.0 volts) for best results and connect the wires (red to red, black to black). Do not let the black and red wires touch. If preferred, you can use other highly stabilized DC power sources with an output of 3.0 volts (or up to 4.5 volts).

Make sure to turn on the laser for at least five minutes before making holograms. Avoid touching the laser for the two minutes just prior to making an exposure, since any disturbance to the laser causes it to become unstable. Finally, avoid cross draft (moving air) across the laser. This affects the laser’s operational stability needed for making holograms.

The holography diode laser included in your kit is classified as Class IIIa, and has an output similar to that of common laser pointers and grocery store scanners. Nonetheless, one should avoid looking directly into the laser beam.

4.0 The Basics of Using Your JD Holography Processing Kits

Optimized by Dr. Tung H. Jeong and his colleagues, the JD holography processing kit provides a convenient and inexpensive alternative to buying and mixing your own chemicals. Just add water to create stock solutions to prepare the Developer and Bleach, as well as Wetting Solution.

For a full understanding of the JD kits and safety measures, we highly recommend you read the instructions and notices that accompany the JD kits. Instructions may also be found online at http://www.integraf.com. The two processes for using the JD kit are significantly abridged here:

(1) Preparing the stock solutions

a. Mix the chemicals with distilled water for Part A, Part B, and Bleach in separate 1-liter bottles.

b. Set up the trays in the following order: Developer, Rinse #1, Bleach, Rinse #2, and Wetting Solution.

c. Pour equal parts of Parts A and B into one tray to form the Developer, enough to submerge at least one holographic plate.

d. Pour the Bleach into a separate tray.

e. Pour distilled water into the Rinse trays.

f. Pour a capful of PhotoFlo into 1 liter of water to form the Wetting Solution.

(2) Processing the holograms.

a. With a rubber glove or tongs, slip the holographic plate into the Developer, preferably with the emulsion side facing upwards to prevent scratching. Hold the plate from the edges.

b. Agitate holographic plate in the Developer until it is dark (it takes 20 seconds to 2 minutes).

c. Rinse with agitation for at least 20 seconds (up to 3 minutes).

d. Agitate the hologram in the Bleach until clear (less than 2 minutes)

e. Rinse again for at least 20 to seconds (up to 3 minutes)

f. Finish the hologram in Wetting Solution for 20 to 60 seconds

g. Dry the hologram by standing the holographic plate vertically (i.e., lean it against a wall)

Though the JD chemicals are termed non-volatile, chemicals do evaporate over time and may cause nose and throat irritations. It’s always a good idea to use the chemicals in a ventilated area and follow recommended safety precautions.

5.0 Viewing Your Hologram

For a reflection holograms made with the instructions above, the image can be viewed after thorough drying. Thorough drying may take minutes to hours, depending on ambient conditions and technique. Transmission holograms, on the other hand, can be viewed with laser light even when wet. You can learn how to make these kinds of holograms online at http://www.integraf.com.

To view your reflection hologram, you need an appropriate viewing angle and light source. With the appropriate light source, view the image by shining the spot light at the hologram from approximately the same angle you had the laser shoot when you were first exposing plate. To see the hologram, you might need to tilt the plate left and right or forward and back to maximize the brightness of the image. It actually takes some practice.

As for the light source, ideally, you want a bright spot light such as that from a slide projector or sunlight. Spot lights concentrate the light using a built-in reflector so that all the light is confined to the correct angle. As an inexpensive substitute, you can use a white LED pin light found at your local retail store. You generally cannot view a reflection hologram using lasers, fluorescent light, or frosted light bulbs.

6.0 Storing Your Unexposed Holographic Plates, Developer, and Laser

To extend their shelf life, your unexposed holographic plates should be protected from moisture and heat. Wrap your box of holographic plates with kitchen plastic wrap or place them in a reasonably air-tight plastic bag. Refrigerate to extend longevity. Holographic plates should be allowed to reach room temperature before opening in order to prevent condensation.

Storage of the JD developer is explained in detail in the instructions that come with each kit or at http://www.integraf.com. Store away from food and children, and always label packages clearly as materials not to be consumed.

Your holography diode can be used for years if used and stored properly. When not in use, place the collimating lens back onto the laser, with or without the spring, so as to avoid dust and dirt from getting into the laser. Then, carefully wind up the wires to the laser without touching the circuit board and place the laser back into the original protective canister.

AFTER YOUR FIRST HOLOGRAM

Congratulations! You’ve made your first hologram and are now ready to make some new holograms. For awkward-shaped, larger, or multiple subjects you need only adjust your system slightly as described below. The rest of the processes (removing the lens from the laser, exposure time, developing procedure, etc.) remain the same. Just remember, the more complex your set up and subject, the more chance there is for movement (and thus a sub-optimal hologram). The rules for choosing your subject still hold (hard, bright, non-deforming).

Non-flat or Awkward-Shaped Subjects

Try using placing your subject in a bowl, tray, or shallow cup, and then placing the holographic plate on top of it. This is particularly useful when you want greater depth or are using larger holographic plates.

Getting a Profile or Deeper Image of Your Subject

Here, you are going to place the holographic plate in a vertical position right next the subject, and then place the laser on the table instead of the tower. For 2.5”x2.5” (63mm x 63mm) plates, you can lean the holographic plate directly against the subject.

You may need a brace in order to keep the plate vertical (about 90 degrees) if you feel the subject and plate cannot be stabilized. A brace is also helpful if you are using larger 4”x5” (102mm x 127mm) holographic plates.

Two sturdy cups can serve as your convenient brace. Alternatively, you could also use two wooden blocks, paper weights, salt and pepper shakers, or anything hard that does not deform or slip on your table (mouse pad or sand tray). Avoid cardboard and books. Books continuously move as air pockets between the pages escape.

Step-by-step for using a brace:

1. Place the two cups apart to form a brace, approximately the same width as your holographic plate.

2. Place the laser (and its cup and clothespin) on the table instead of the tower (vase), so the subject and laser are at the same level.

3. Position the laser until the object is optimally and fully illuminated. Place the laser about 1 foot (30-40cm) away from the subject. To help see the beam, place a white card (or piece of paper) behind the object and adjust the laser while looking at the shadow on the card.

4. Block the laser light with your book (shutter) and prepare your holographic plate.

5. Place the holographic plate between the laser and the object, leaning against your two cups (brace).

6. Expose and process as previously described.

Other Kinds of Holograms

With your holography kit, you can also make several other kinds of holograms.

A transmission holograms that can be viewed by laser light and even projected onto a screen

A multi-image hologram

A hologram that lets you see how much an object deforms over time or due to stress (one student made a hologram of a mushroom and showed that it grew in a span of a few minutes!)

A diffraction grating to observe the spectrum of sunlight showing what elements are there (front-surface mirror required)

Information on how to make these holograms can be found in your booklet Laser Holography—Experiments You Can Do. Also see http://www.integraf.com for frequently updated tutorials, tips, and articles.

TROUBLE SHOOTING

Below are some common issues that holographers experience when making a hologram, especially for the first time, along with some key questions and possible solutions.

“I don’t’ see any image at all.”

Chances are very high that your system encountered vibration or movement.

Was there some air current blowing onto your holography system?

Was the object as your subject hard and bright?

Was the laser really placed stably?

Was the room generally still and quiet around the exposure time?

Did anyone touch the table during exposure?

Did anyone sneeze or talk aloud?

Remember that the longer you expose the holographic plate to the laser light, the higher risk you run of encountering vibrations (and thus getting no image at all).

Laser lost frequency stability

Make sure the laser warmed up for at least five minutes

Avoid air drafts

Avoid touching the laser during two minute prior to exposure

The hologram has not completely dried yet

Though it may look dry, the hologram may still be moist. Try waiting a little a few minutes longer or even an hour, depending on ambient conditions.

Hologram is not viewed correctly

View under appropriate lighting. Florescent and frosted light bulbs do not work.

View the hologram from the front side and same angle that the laser exposed it.

“I see an image but it’s dim”

The object may not be bright enough. Pick something white or bright metal.

The object may have moved slightly. Make sure the object is hard and does not deform.

Check to see if your laser is fully and directly illuminating your object and plate area.

Try increasing exposure time by a few seconds (not too much longer)

Try bringing the laser closer to the object, while still allowing full illumination.

Check that that you are using distilled water. (Tap water may contain impurities or minerals.)

“My holographic image is there but seems foggy or has streaks and spots”

Make sure your developing the hologram with sufficient time in each step.

Try rinsing longer (up to 3 minutes) between the developer and bleach steps.

See that the wetting solution is evenly applied when removing the hologram

Watch out for drips and droplets when hanging drying the hologram.

“My hologram looked great two weeks ago, but now it’s kind of faded”

Try rinsing longer (up to 3 minutes) between the developer and bleach steps.

Avoid leaving the hologram under direct sun. Just like photos, holograms fade can fade.

Read more:http://www.integraf.com/instructions_web.htm#ixzz1ldWWQTAX

Simple Holography

The Easiest Way to Make Holograms

By T. H. Jeong, Raymond Ro, Riley Aumiller (Lake Forest College)and Misashi Iwasaki (Kyoto Institute of Technology)

with contributions from Jeff Blythe (University of Cambridge)Edited by Alec Jeong

Copyright © 1996-2009

1. INTRODUCTION

"Everything should be made as simple as possible, but not simpler” - Albert Einstein

We attempt to follow this dictum so you can make holograms easily. The procedures we propose herein are as simple as it is physically possible. In the process, we make holography not only as simple as possible, but safer, less expensive, and more accessible to young people.

Most of the essential items described in this article can be found in Integraf'sholography kitsor are available separately. The kits provide materials for you to make many kinds of holograms, including reflection holograms andtransmission holograms.

2. THE LASER

The figure below shows a Class IIIa diode laser with an output of 3 to 4 mW when operated by 3.0 v dc. If the power is supplied by batteries, its red light of wavelength 650 nm achieves a coherence length exceeding 1 m after a warm-up period of a few minutes. The traditional helium-neon laser, on the other hand, operates on dangerously high voltages, is prone to breakage, has a shorter shelf life, and a coherence length of approximately 30 cm.

Unlike many laser diodes and laser pointers, the laser shown below and in our catalog has a stabilized frequency output (a must for holography), good coherence length (also a must), and a removable collimating lens. With the spring-loaded collimating lens mounted on the laser, the output beam can be adjusted to focus at any arbitrary distance.

To make holograms, we'll actually take off the collimating lens . . . shining this pure beam right on to the holographic plate and object.

To make holograms, we'll actually take off the collimating lens. Without the lens, the direct output from the laser spreads out with a highly eccentric elliptical profile. Since the beam encounters no external optical elements, the light has no mottled patterns caused by interference and diffractions, and appears perfectly clean. In other words, we'll be shining this pure beam right on to the holographic plate and object.

The responsible parent or teacher is advised to remove the lens and the small tension spring before allowing the student to use the laser. This way, the power density received by human eyes will not exceed that received when looking at an ordinary grocery store laser scanner. When the laser is not in use, replace the collimating lens (with or without the tension spring). This helps ensure that you won't lose the lens and, more importantly, will help keep dust out of the laser.

If you are using your own "laser pointer" for making holograms, know many laser pointers and diodes do not have frequency stabilizing circuits (like the one above), which is required for holography. Moreover, since most laser pointers do not have a removable collimating lens, you must buy a special optical lens to spread the beam. With two lenses (four lens surfaces) through which the laser beam must shine, there may be many objectionable patterns on the resulting beam due to the four lens surfaces and the dirt on them.

3. STABLE SUPPORT FOR LASER

An excellent support for such a small laser is a wooden clothespin, as shown below. For mechanical stability and maneuverability, the clothespin holding the laser is stuck into a cup of sand, salt, or sugar (not pepper!). On the other hand, for schools with available laboratory hardware, the clothespin can be glued to a rod and mounted on a lab stand with a right-angle clamp.

The wooden clothespin offers another advantage. It being a thermal insulator, the laser will reach thermal, electrical, and frequency stability a few minutes after it is turned on, assuming batteries are used as its power source. An alternative support would be a rubber-tipped thermometer holder.

4. REFLECTION HOLOGRAM BY “CONTACT COPY” METHOD

The “white light reflection hologram” is the simplest to make. We advocate the “contact copy” method, whereby you lean the holographic plate (holoplate) directly against the object during exposure. As long as there is no relative movement between the object and the plate, no vibration isolation is needed.

4.1 Supplies

You will need the diode laser discussed above, a supply of Slavich PFG-03M 2.5 x 2.5 inch plates (63mm x 63mm), and a JD-4 processing kit (or PFG-01 plates with JD-2). All of these items are included in the HOLOKITTMHolography Kitsthat can be purchased fromIntegraf's catalog, and will make both reflection and transmission holograms. Detailed instructions accompany the the kit.

Though slightly trickier, one can also use PFG-01 holographic film sheets sandwiched and clipped between two glass plates instead of using holographic plates. Develop with JD-2. For the instructions below, substitute the properly sandwiched film sheet for the holographic glass plates. See our article on how to useholographic film sheetsfor important details.

4.2 Preparing the object

The choice and preparation of the object is crucial: (1) it should be made of a solid material such as a quarter or dime (no furry or fabrics); (2) it must appear bright when illuminated with the red laser light; and (3) it must not move or deform.

If it's your first time making a hologram, try to avoid choosing objects that are fabric or fury (e.g. teddy bears) because these objects deform easily. Also avoid

large plastic objects as they tend to expand and contract with the slightest change in temperature (even from the heat of your fingers!). For best results, try metal or porcelain objects that can be easily illuminated with laser light and are no larger than the size of the holoplate, such as coins.

If there is any doubt about potential movement, you could glue the object to a stable wood or metal platform where the hologram will be made. The picture below shows a more elaborate, but optional, way of mounting the object. The object is glued to a small platform and held from behind by a metal block to prevent the object from leaning back. The platform has three round-headed screws from the bottom for three-point support. The upper parts of two of the screws can be used as stops when the holographic plate is placed in front of the object for exposure, preventing any slippage.

Holography Tip

If your object or holographic film plate moves even 1/1000th of an inch during exposure, your hologram will not likely turn out. So avoid talking, music, noise, walking around, air currents, creaky floors, soft objects, temperature changes to the object . . . . What other things can you think of that might cause tiny movements or vibration?

Another way to dampen movement or vibration is by placing the object on a computer mousepad, or even better, a tray of sand, salt, sugar (or even kitty litter).

Prepare the chemical processing solutions and layout the processing trays as directed by the instructions that accompany theJD-4 (or JD-2) kits. Although our chemicals solutions are termednon-volatile, chemicals evaporate over time and may cause nose and throat irritations. Use the chemicals in a ventilated area.

It is not necessary to have a completely dark room. However, the room should be sufficiently dark so that one cannot read in it. Use a standard night-light if necessary so that you can move about safely. Block any direct light from reaching the holography system.

4.3. Making a reflection hologram

Carefully follow these steps to align and expose the hologram to the laser:

1. Adjust the laser in its holder so that the beam spreads out horizontally.

2. Place the object at a distance of 35 to 40 cm from the laser.

3. Place a white card behind the object and adjust the laser while looking at the shadow on the card. Adjust the position of the laser until the object is optimally illuminated. Then remove the white card.

4. Place an opaque cardboard near the laser to block the light from reaching the object. This will serve like the shutter of a camera.

5. Remove a holographic plate from its container (in the darkest part of the room), and close the container.

6. Lean the holographic plate on the object, making certain it will not slip or move; the emulsion (sticky side) should touch the object.

7. Allow 10 seconds for the object to settle, and tell everyone in the room to hold still.

8. Now, lift the “shutter” slightly off the table while still blocking the laser light, and wait 2 seconds for the vibration to subside.

9. Then, lift the shutter all the way up to expose the holographic plate and object for 10 seconds (5 seconds minimum, longer is OK up to 40 seconds). Then, block the light again.

10. Finally, process the exposed holographic plate according to instructions that accompany theJD-4(orJD-2if you are using PFG-01 plates or film sheets).

11. Optionally, place your holographic plate in a solution ofPhotoflo for 20 to 30 seconds. Photoflo is a wetting agent that helpsholograms turn out cleaner and clearer.It reduces streaks and promotes more uniform and quicker drying.While PhotoFlo is not required to make a hologram, it does help them look better.

After the hologram is thoroughly dried, it can be viewed with a point source of incandescent light such as that from a projector, flashlight, or the sun. You cannot use diffused light sources such as frosted bulbs and florescent lamps. For best results, spray paint the emulsion (sticky) side with a diffuse black paint. This protects the emulsion and provides a dark background to enhance the visibility of the image.

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5. MAKING A PANORAMIC TRANSMISSION HOLOGRAM

Making a transmission hologram is just as easy asmaking a reflection hologram. The only difference is really in your initial set up the position of the laser, film plate, and object.

Transmission holograms offer many advantages over reflection holograms. For example: (1) the object or scene can be much bigger than theholographic plate; (2) when illuminated with the diode laser, the entire virtual image is sharp; (3) the real image can be projected onto a screen using a laser pointer; (4) it is more tolerant of vibration during recording, so that film, instead of the more expensive plates, can be used; and (5) two or more “channels” of independent images can be recorded on the same plate or film. For example, after the first exposure, turn the plate or film upside down and exposure again with a different object. Each exposure should be one-half the duration of one full exposure.

The figure below shows a “sandbox” system set up for recording a panoramic transmission hologram on a strip of film with approximate dimensions of 4"x5" (102mm x 127mm). The film is Slavich PFG-01 (which must be processed with JD-2 or JD-3) and can be cut (in a darkened room, of course)into any smaller sizes using scissors or paper cutter. One can also use a holographic plate. PFG-01 and PFG-03M both make great holograms, but PFG-01 is especially good for transmission holograms.

Thefilm is clamped between two larger glass platesand stuck into the sand. One side of the spreading beam serves as reference beam and the rest illuminates the object(s). Since air is trapped inside the glass plates and escapes slowly, the film sandwich will have movement over several minutes. It is advisable to squeeze out the air by pressing the sandwich between two flat surfaces. Alternatively, just place the sandwich in position and wait 5 to 10 minutes before exposure. Cover the film and keep any stray light from fogging it during this time.

The exposure time is approximately 30 to 60 second (PFG-01). The processing procedure for the film, using JD-2 or JD-3, in accordance with instructions that accompany the kits.

For more details on making transmission holograms, see our article"How to Make Transmission Holograms".

6. CONCLUSION

We have presented the simplest and least expensive method of making holograms. This type of project can be taught as art, craft, or science and technology in the elementary schools, before students have decided on their future occupation. Once interested, students will be induced to learn all the fundamental principles of optics and photonics: reflection, refraction, interference, diffraction, polarization, coherence, and scattering.

7. ADDITIONAL INFORMATION

USE OF THE WHITE CARDBOARD: The white cardboard placed behind the object is for observing the silhouette to ensure that the object is illuminated as evenly as possible. Assuming that this cardboard is opaque, you can use it as the “shutter” by moving it to a position between the laser and the object (see step 4 in Section 4.3).

LASER PREPARATION:

Make sure the laser has been warmed up for at least 5 minutes before any holograms are exposed. Minimize any disturbance to the laser (do not touch it or even allow moving air to cross it) which may cause the outputs to become unstable.

HOW TO OBSERVE THE IMAGE IN THE FINISHED HOLOGRAMS:

To view your hologram, you need to make sure you're using the correct light source from the appropriate angle. See our article"How to View Your First Hologram"for details.

SETTING UP A SIMPLE LAB IN A CLASSROOM

When setting up your lab in a classroom for multiple students, you may want into account some of the practical considerations such as how you set up your "assembly line" for students to expose and develop their holograms. See our article"Teaching Holography in Classrooms"for details.

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How to MakeTransmission Holograms

By Alec Jeong and Dr. T. H. Jeong

Copyright © 2005 Integraf LLC. All rights reserved.

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1. INTRODUCTION

Transmission holograms are actually quite easy to make andhave unique features that can truly dazzle any student, teacher, or viewer.

Making transmission holograms requires the same materials as those needed for making a reflection hologram. In fact, many of the methods and processes for making transmission holograms are also exactly the same as those for making reflection holograms. The only real difference lies in how you position the materials on your work table.

If you have not already done so, we recommend you familiarize yourself with the basics of making reflection holograms prior attempting to make transmission hologram. Simply read our short article “Simple Holography” or download ourstep-by-step instructions. These articles will

give you some background on the materials involved, basic preparation, how to choose the subject, steps for exposure and development, etc.

All the essential materials for making transmission holograms can be conveniently found in Integraf’s HOLOKIT hologram kits, or purchased separately.

2. TRANSMISSION HOLOGRAMS

Transmission holograms constitute one of the two major types of holograms, the other beingreflection holograms. All other holograms (rainbow holograms, computer generated holograms, multi-channel holograms, computer-generated holograms, etc.) are actually hybrids of these two types of holograms.

The typical transmission hologram is viewed with laser light, usually of the same type used to make the recording. This light is directed from behind the hologram and the image is transmitted to the observer’s side. The virtual image can be very sharp and deep. For example, through a small hologram, a full-size room with people in it can be seen as if the hologram were a window. Of course, making holograms of people requires a more powerful laser and significant safety precautions, but you get the idea. Transmission holograms are like a window to another world. Remember Alice in Lewis Carroll'sThrough The Looking Glass?

Unique Features of Transmission Holograms

There are some unique features of transmission holograms that"wow" the viewer:

Captures an image of a subject much bigger than the holographic plate or film sheet that records the hologram. Reflection holograms cannot do this easily.

Have an image can be projected onto a screen or other surface with a laser. Can be broken into small pieces whereby each piece still contains the entire

image. Yes, that's right. If you were to smash a hologram with a hammer and thenshine a laser through just one piece, the entire image can be still be projected and viewed.

Can record more than one image on the same holographic plate of film sheet; in effect, adding a “channel” for subsequent images. When viewing the finished hologram, you can “tune” to different channels by rotating the hologram and see your different images!

Drawbacks of Transmission Holograms

Notwithstanding the unique features above, transmission holograms are usually not the first hologram of choice for artists, hobbyists, and first-time holographers. The main reason for this is due the fact that transmission holograms must generally be viewed with laser light instead of white light. Practically speaking, this makes transmission holograms less convenient than reflection holograms to display.

2.EQUIPMENT AND MATERIALS FOR MAKING TRANSMISSION HOLOGRAMS

To make transmission holograms, you use the same equipment and materials you use for making reflection holograms, as explained in “Simple Holography”.

Essentials

Material NotesHolographic Plates (or Film) PFG-03M and PFG-01 emulsions both make

excellent holograms, but PFG-01 is especially good for transmission holograms.

Diode Laser for Holography Red sensitive (650nm)

3mW to 5mW (Class IIIa)Removable collimating lensStabilized power and frequencyCoherence length of approximately 1 meter

Clothespin To hold the laserChemical developer & bleach

Use JD-2 or JD-3 kits (with PFG-01)Use JD-4 kit (with PFG-03M)

Five developer trays Three small ones, and two large onesPhotoflo solution To help avoid smudges on

the finished hologram

The above materials can all be found in thehologram kitor catalog provided by Integraf. While the HOLOKITS come standard with PFG-03M, you can request to substitute this emulsion with PFG-01 (with JD-2 developer).

Other accessories generally recommended area computer mouse pad, a cup of sand (salt or sugar will also work), a hardcover book (or piece of cardboard) to serve as a shutter, coins (or other appropriate object as the subject for your hologram), distilled water, and a hair dryer (optional). Again, please see"Simple Holography"or the downloadablestep-by-step instructionsto understand how these items are used.

Now, your ready toset up to make transmission holograms. . ..

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How to Make Transmission HologramsCopyright (c) 2005 Integraf LLC. All rights reserved.

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4. YOUR SET UP

The only real difference between making transmission holograms versus reflection holograms lies in how you position the materials equipment on your holography work space for the exposure.

To illustrate how to make transmission holograms, let's compare the set up for making reflection holograms versus making transmission holograms.

Reflection holograms.In making reflection holograms, the holographic plate is placed between the laser light and the object in one of two basic ways. The order from right to left is:

object > holographic plate > laser. (a) From the top down at a 45 degree angle, with the holographic plate on top of flat objects, such as coins in this case; or

(b) From the side for larger, bulkier objects, such as a chess piece in the case below.

Transmission Holograms.In contrast, making transmission holograms requires the holographic plate to be placed behind the object and laser, or to the side at 45 degree angle or so. The idea is that the laser light that reflects off the object will interfere directly with the light coming from the laser in front of the plate and then get recorded as such. This creates the "deep scene" hologram.

There are two recommended set ups for making transmission holograms with a single laser beam (as opposed to split-beam using mirrors and lenses, etc.). The first is the "top-down" version, which is useful for deep scenes of flat objects. One can achieve depth of over 6 inches (15cm) with this method.The order from right to left is: holographic plate > object > laser. Note how the bulkier object (the chess piece) is off to the side, so as to avoid casting unnecessary shadows on to the plate.

An alternativeset up is the "straight-on" or "same-plane" method, whereby the laser shines straight on from the same horizontal plane as the object and plate. The object and plate are split apart at about a 90 degree angle to each other, with the beam shining at each with equal intensity. This second method is appropriate for bulkier items. This set up helps prevent the object from casting too big a shadow on to the plate. After all, who wants to make a hologram of a shadow?

The photograph below shows how you can set up to make transmission holograms at home using holographic plates. To learn how to use holographic film instead of plates, see our article"How to Use Holographic Film".

(Above) A close up shot that details on how one can easily hold the laser with a clothespin stuck into a cup of sand (salt, or sugar).

A homemade stand is used to hold the holographic plate up vertically. You can simply clip the holographic plate on two sides with two metal clips, and then use magnets to hold it down onto a sturdy, flat sheet of metal. An even simpler way is to lean the plate against two flat, non-moveable objects, such as heavy book ends. For the above options, place your holder on top of a computer mouse pad. The mouse pad serves to dampen vibration and keep the holder from slipping on your table.

The picture below shows how to prepare the homemade plate and object holder. Use a piece of hardwood about 4” x 8”, paint it white, and install two 3” screws about 2” apart. Place this platform on top of a mouse pad and arrange the ensemble as shown in Figure 1.

Prepare the chemicals and your “dark room” as discussed in “Simple Holography”. Use a book as shutter shown in Figure 4.

5.READY FOR ACTION

Rotate the laser (handle with care, do not touch the electronic circuit board on the laser) until its elliptical beam of light is fanned out vertically so that the strongest part of the light is

illuminating objects (coins are best) on top of the white platform; while a weaker part illuminates the position where the plate will be placed. Use a piece of 2.5”x2.5” white paper instead of a real plate for lining up purposes. Then block the beam with the book (shutter) and turn off the normal light. Allow the laser to warm up at for five minutes without any physical disturbance.

Viola! You are ready to make transmission holograms. Notice that in making transmission hologram, all laser light approach the plate from the same side. Whereas, in making a reflection hologram, the reference and object beams hit the plate from opposite sides. In both cases, the emulsion side of the plate should face the object.

The rest of the steps for making a transmission hologram are the same as that for making reflection holograms. See"Simple Holography"for details on such as steps. Assuming the distance between the laser and the plate isabout 30-40 cm, the exposure time using either PFG-01 film or plates or PFG-03M plates is approximately 10 seconds, when using a 3-4mW laser. That's it!

6. VIEWING YOUR TRANSMISSION HOLOGRAM

There are two ways to view your transmission hologram, both of which require youuse laser light.

SEEING THE VIRTUAL IMAGE.By shining the light from the laser that recorded it, as shown below, you will see the so-called virtual image of the objects exactly as if there are still there! Sometimes you have to adjust the angle to see the image. Another way to view the virtual image is to put the plate back to the location where is was recorded and allow the laser light to illuminate it. Block the light that lights up the plate from where the object was, and you will see the image of the objects instead. Keep the lens off the laser, so the light is spread out.

CAUTION: LASER LIGHT

Avoid looking directly into the laser light, since that could be harmful to your eyes. Instead, focus on the hologram and view it from an angle. With a 3-4mW laser, such as the one in Integraf's HOLOKITs, your natural blink reflex is generally sufficient to protect your eyes. Going beyond momentary exposure to the laser light can be harmful.

PROJECTING THE IMAGE. Now take the laser off the clothespin and screw back the lens (without the spring) can came with it. Adjust the lens until the laser becomes a “pointer” (forms a small spot at a long distance). Now direct the laser through the finished hologram in a direction opposite to one during the recording. The “real” image is projected back on the white platform. When you turn off the room lights, and you will see this image.

NOW, LET''S BE OUTRAGEOUS! If you want to be dramatic, smash the hologram into little pieces, pick one piece up (bigger than the beam diameter of the laser) and an entire image can be projected (providing you find the right orientation by trial and error.)

6. CONCLUSION

So, making transmission holograms is really quite easy, isn't it? And it's not much different than making reflection holograms, except where you place the holographic plate relative to the object and laser. With its unique characteristics and dazzling viewing potential, transmission holograms are excellent choice forclassroom demonstrations, along with reflection holograms.

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Hologram Science ProjectsJunior High and Senior High School Students Can Do

By Alec Jeong

Copyright © 2006 Integraf. All rights reserved.

1. INTRODUCTION

This article introduces you to nine easy to advanced hologram projects teachers and students can do simply and affordably.

Each year, we serve a solid number of junior high, senior high, and college students who choose to make holograms for a science project or a science fair. Many of these students go on to win their science fair at their school, regional, and state levels. Regardless of winning a science fair or not, students get first-hand experience in holography, a field that covers five Nobel Prize ideas.

2. WHAT HOLOGRAM SCIENCE PROJECTS CAN I DO?

Hologram science projects for first-time holographers range from basic to slightly more complex experiments. Many school or science fair projects usually require use of the "scientific method". So, in our hologram project descriptions below, we've listed the variable that can be changed in each hologram experiment and some hypothetical questions to get you going. We've also briefly mentioned how each hologram science experiment relates to real-life applications.

Before pursuing the the projects described below, we recommend you first make a basic reflection hologram, which is quite easy to do and can be accomplished in about a hour or two (see "Simple Holography") . Doing this first will give you the necessary grasp of the fundamentals before you change variables (that is, "experiment") with your set up. In some cases, you may also want to make a transmission hologram as well, which is just as easy to do (see "How to Make a Transmission Hologram")

TIP: When using the "scientific method", change only one variable at a time and keep everything else constant. This way you can determine the relationship between the variable and the result.

INDEX OF HOLOGRAM SCIENCE PROJECTS FOR FIRST-TIME HOLOGRAPHERS

BASIC Exposure TimeDeveloper Time or TemperatureMaterial of ObjectTemperature of Object

INTERMEDIATE Multi-Channel Hologram MemoryNon-Destructive Testing . . . of a F-16 Fighter Jet

ADVANCED Growing Mushrooms

OTHER Holograms of Holograms (H1/H2)Diffraction Gratings

BASIC HOLOGRAM SCIENCE PROJECTS

Basic Project #1: Exposure Time <Index>

Variable. Change the amount of time you expose the holographic plate and object to the laser.

Hypothetical Questions. Will the hologram be brighter or darker? Will it change color? Does over-exposure do anything? Why?

Real-Life Application.Determining the optimal exposure time is what professional holographers grapple with everyday.

Why is this interesting?You'll be surprised with the results, because it's not what you normally think. While holography share some similarities to photography, the physics of it actually has some differences.

Basic Project #2: Developer Time or Temperature <Index>

Variable. Change the amount of time you process the exposed holographic plate in the chemical developer, or change the temperature of the chemical solutions slightly.

Hypothetical Questions. Will the hologram be brighter or darker? Will it change color, and if so, what colors? Why?

Real-Life Application.Just like in photography, the quality of the image in holography is dependent just as much on the initial exposure as on the development process. Professional holographers are able to make single-color holograms appear full-color! How is that possible?

Why is this interesting?Again, you'll be surprised with the results, because it's not what you normally think. Hint: Read up on wavelengths and photographic emulsions to understand why the results turn out the way they do.

Basic Project #3: Material of Object <Index>

Variable. Change the material from which the object of your hologram is made, i.e. try metal, wood, plastic, and paper.

Hypothetical Questions. Will the hologram turn out exactly the same, or will there be some good ones and some non-existent ones? Are there unusual patterns that form on the image? Why?

Real-Life Application.The hologram of an eagle on the Visa credit card uses a physical model, likely made of porcelain or hard plastic. Professional holographers choose their material wisely.

Why is this interesting?Choice of material can make or break your hologram. The interesting part is why. Hint: Ask yourself, are "solid" objects really solid or do they move, and if the hologram capturing the "image" or is it capturing microscopic interference patterns?

Basic Project #4: Temperature of Object <Index>

Variable. Slightly change the temperature of the object used as the subject of your hologram between different exposures, using the same or new holographic plate.

Hypothetical Questions. Are there unusual patterns that form on the image? Do some holograms turn out while others do not? Why?

Real-Life Application.Engineers have used holographic principles to understand the effect of heat and cold on materials. For example, what happens to certain car engine parts during the winter versus the summer? What material should they use to make that engine part?

Why is this interesting?Holograms capture microscopic movements in a way that photographs cannot do.

INTERMEDIATE HOLOGRAM SCIENCE PROJECTS

Intermediate Project #1: Multi-Channel Hologram Memory <Index>

Variable. Change the angle of the holographic plate and the object to make a multi-image hologram on a single holographic plate.

Hypothetical Questions. How many different images can be produced on a single plate? Is there a theoretical limit to this number, and how can one try to approach that theoretical limit?

Real-Life Application.This leading edge technology is what allows CD-ROMs and DVDs to hold so much data! In fact, the newest wave of recordable CD-RW by InPhase, Sony, and others, will have a capacity of 300 GB. In five years, it's expected to reach one terabyte (which is giga-gigabyte).

Why is this interesting?See our article onHolographic Data Storage.

Intermediate Project #2: Non-Destructive Testing . . . of a F-16 Fighter Jet<Index>

Variable. Change the amount of stress on the object of the hologram, by placing a weight on it, making an exposure, taking off the weight, an then making a second exposure on the same holographic plate.

Hypothetical Questions. Will the hologram turn out? If so, what do you expect to see in this holographic image?

Real-Life Application.These holographic principles are used by civil, mechanical, and aeronautical engineers to find out how stress effects materials and machines. In fact, at one time, holographic interferometry was once used to see how much many g-forces an F-16 fighter wing can take under simulated combat situations.

Why is this interesting?Holographic interferometry and its derivations allow you to see microscopic changes. Well, you probably won't be able do testing on an F-16 without getting arrested by the CIA or military, but you can try these experiments on a model plane or toy car.

ADVANCED HOLOGRAM SCIENCE PROJECTS

Advanced Project #1: Growing Mushrooms <Index>

Variable. Show how much a mushroom grows in 2 minutes. Hypothetical Questions. Do mushrooms continually grow? Can one really see

such differences in growth? Real-Life Application.Called holographic interferometry, this experimentation

method is the basis of many techniques for measuring microscopic movements. This project was undertaken by one of our customers about over 10 years ago as part of a science project. Not surprisingly, this student went on to win his science fair and more.

Why is this interesting?Amazingly simple in theory, doing this project successfully requires you to develop a solid understanding of making holograms. The amazing fact is that all this can be accomplished with the simplest of materials and equipment, as with the other basic and intermediate projects above. With the knowledge you gain from this project, you can easily go on to more even more advanced projects, such as split-beam holography.

OTHER HOLOGRAM SCIENCE PROJECTS

Unlike those listed above, there isn't really any "variable" to change in the projects in this section. Rather, these experiments are meant to teach you the basics of the practice of advanced holography. Contact us if you 'd like to make these holograms. We'd be happy to give you guidance.

Other Project #1: Holograms of Holograms (H1/H2) <Index>

Task.Make a hologram (H2) of a master hologram (H1) Observations. Have you ever wondered how to make a hologram that really

sticks out in front of the frame? Well, this H1/H2 technique is how it's done. One

makes a master hologram, and then makes a copy hologram of that hologram. The basic principles in H1/H2 holograms is also used in mass-produced holograms, such as those on your credit card, passport, or security labels.

Other Project #2: Diffraction Gratings <Index>

Task.Make a holographic diffraction grating Observations.A holographic diffraction grating is basically a hologram of a ray of

light. Diffraction gratings are commonly found in monochromators, spectrometers, sunglasses, and even nature, i.e. iridescent butterfly wings. Scientists frequently use diffraction gratings to study light, and even to determine the elements that make up our sun.

Note. This project requires you to have a front-surface (also known as first-surface mirror, around $15). The rest of the supplies are the same as those for the other projects listed on this page.

3. WHAT SUPPLIES DO I NEED?

All the hologram science projects above require only the simplest of supplies and equipment, costing around $100 or so. Most of the essential items described in this article can be found in Integraf'sholography kitsor are available separately. The kits provide materials for you to make many kinds of holograms, including reflection holograms andtransmission holograms, and include step-by-step instructions for making reflection holograms. If you prefer to purchase materials separately, you'll need those listed in our article "Simple Holography" and our downloadableStep-by-Step Instructions. At the very least, you will need an appropriate diode laser for holography, a supply of Slavich PFG-03M 2.5 x 2.5 inch plates (63mm x 63mm), and a JD-4 processing kit (or PFG-01 plates with JD-2). You do NOT need vibration-proof tables or specialized equipment to do the hologram projects listed on this page.

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How to Use JD-2Holography Developer and Processing Kit

Copyright © 2007. Integraf LLC. All rights reserved.

Portions of the instructions below are based on articles written byTung. H. Jeong, Riley Aumiller, Raymond Ro, and Jeff Blyth

JD-2 HOLOGRAPHY PROCESSING KIT

The JD-2 holography developer and processing kit provides all the chemicals needed for making holograms using Slavich PFG-01, VRP, VRP-M holographic plates and film sheets (for PFG-03 and "BB" emulsions, useJD-4). Simply mix the dry chemicals in the JD-2 kit with water to create the developer components and bleach solution. This article explains step-by-step how to do this and use the JD-2 holography processing kit to make holograms on plates. If you are using holographic film sheets, remove the film sheet from your film holder after exposure before processing.

Important NoticeThe following instructions for using the JD-2 holography processing kit have been modified from the actual

instructions found in each package of JD-2. Instructions provided in this article are for your convenience only. For your safety and thorough understanding of JD-2, you should rely on the instructions and chemical safety notices that come inside each package of JD-2.

Like many common household cleaners, JD-2 contains chemicals and should be treated with respect. Please read all the warning labels on each package. It is good practice to use eye goggles, dust mask, apron and rubber gloves when mixing chemicals. While the chemical solutions have low volatility, working in a ventilated area is recommended. You can download a copy of the MSDS for JD-2 holography processing kit from this website.

MIXING THE STOCK SOLUTIONS

The chemicals in this JD-2 kit are used to prepare approximately 1000ml of each of three solutions. You will need to add de-ionized or distilled water, which can be purchased at your local grocery store. It is best to use distilled water that contains no other chemicals although distilled drinking water, which sometimes contains small but negligible amounts of other chemicals, can also be used. Water from your tap generally contains fluoride and other impurities that may reduce the quality of your hologram. For efficiency and safety, teachers or an adult should pre-mix the solutions.

Part A Solution(1000ml)

CHEMICAL AMOUNT

Catechol 20 grams

Ascorbic Acid (powder) 10 grams

Sodium Sulfite 10 grams

Urea 75 grams

ADD Distilled water 1000 ml

Part B Solution(1000ml)

CHEMICAL AMOUNT

Sodium Carbonate, Anhydrous 60 grams


Bleach Solution(1000ml)

CHEMICAL AMOUNT

Potassium Dichromate 5 grams

Sodium Bisulfate 80 grams


Use three 1 liter (or larger) size clean glass or plastic bottles with leak-proof caps. Label themPart A, Part B,andBleachrespectively. To help dissolve the chemicals, you can heat the water until it is luke warm. Optionally, you can also prepare each solution in a clean beaker and then pour the solution into the bottle.

PART A. Fill the bottle marked Part A with roughly 1000 ml of warm distilled water. Dissolve each chemical one-by-one, in any order. Tightly cap the bottle.

PART B.Follow a similar procedure to mix mix Part B.

BLEACH.Follow a similar procedure to mix the Bleach; again, dissolving each chemical one-by-one, in any order.

All solutions last for many months if capped tightly and stored at room temperature. Refrigeration will increase shelf-life.Store it in a safe place away from food and children.

Holography Tip

To extend the shelf life of Part A, protect it from oxidation. To do so, subdivide the solution into smaller bottles so that the unused portions are in full-capped bottles, with little or no air space. For example, try preparing two 500ml bottles for Part A instead of one 1000ml bottle. Refrigeration also slows down oxidation. Do not refrigerate Part A with food to avoid possible mistaken identity as food. When stored appropriately, Part A can last for months.

Note that once solutions A and B are mixed together, the resulting developer solutions lasts only several hours. So, don't mix A and B together until you are ready to make holograms.

HOLOGRAM EXPOSURE

For detailed instructions on making holograms, please see our article“Simple Holography”. Before making your exposures, you should mix and prepare your chemicals as follows.

PREPARATION

Have the following items on hand:

Your pre-mixed JD-2 Part A, Part B and Bleach Solution. 1 additional gallon (4 liters) of distilled or de-ionized water for best results. Tap

water may also work, but not as well. Avoid hard water. 2 small glass or plastic trays, just large enough so that the hologram you are

making can be submerged in a horizontal position. 2 large glass or plastic trays to hold 1 liter of distilled water for rinsing. Tap

water may also work. 1 large tray (optional, but recommended) to hold 1 liter of distilled water

mixed with about 1 ml of photographic wetting agent such as PhotoFlo. You can also use a small tray with less wetting agent, but you should replace the solution after a few holograms.

1 rubber gloveNow label one small tray as Developer A&B. Then, mix equal portions of Part A and Part B, enough so that the hologram to be developed can be totally submerged. Once mixed, the combined A&B solution can be used to develop several holograms, and lasts several hours.

Next to the developer tray place a large tray with one liter of distilled water. This will be used as a rinse.

Next, label another small tray as Bleach. Put enough bleach into it so that the hologram can be totally submerged.

Next to the bleach place another large tray with one liter of distilled water. This will be used as a rinse.

Optionally, place a large tray with the wetting solution in 1 liter of distilled water. Using a wetting solution is optional but recommended. It allows the hologram to dry evenly, thus helping you prevent smudges or streaks.

Check the order of the trays: developer A&B, rinse, bleach, rinse, wetting solution.

Developer >> Rinse >> Bleach >> Rinse >> Wetting

A&B Solution

PROCESSING PROCEDURES

After the holographic plate is exposed, hold it by the edges with your glove hand (or tongs). Keep the emulsion (sticky) side facing upwards to protect the emulsion from accidentally scraping the bottom of your developer tray. Holographic plates should be developed at room temperature.

1. Develop:Quickly submerge the plate into the developer so that all parts get wet evenly. Slush it around for about two minutes. The hologram should turn almost black.

2. Rinse: Rinse the developed hologram with agitation for at least 20 seconds. For best results and longer lasting holograms, rinse up to three minutes to make help ensure that all of Part A has been rinsed off.

3. Bleach: Place the rinsed hologram into the bleaching solution; agitate it until the plate is completely clear (this may take up to two minutes); then, bleach for another 10 seconds.

4. Rinse again:Rinse the bleached hologram with agitation for at least 20 seconds (up to 3 minutes).

5. Finish in wetting solution:Optionally, place the finished hologram in this solution for about 20 seconds. Then, remove the hologram to dry. For best results, avoid streaks or runs as you remove the hologram from the solution.

Holography Tip

After bleaching, the hologram is safe to process with the lights turned on. This allows you to observe if your wetting solution has been evenly distributed on the hologram and if there are any runs or streaks. Hold the holographic plate from the sides to avoid potential dripping of solution from your fingers down the hologram.

The hologram is finished except for drying. A good way to dry the hologram plate is to stand it against a vertical surface with the bottom edge resting on a hand-towel or tissue paper. Best results are obtained when it dries naturally in clean, dust-free air. However, if time is limited, the hologram can be quick-dried by holding it vertically and blowing warm air across it with a hair dryer. For holographic film sheets, hang up vertically to dry, using clean and dry clothespins.

For a reflection hologram, the image can be viewed after thorough drying, using the laser light that exposed it or an incandescent spotlight. Thorough drying may take minutes to hours, depending on ambient conditions and technique. Transmission holograms, on the other hand, can be viewed with laser light even when wet.

STORING HOLOGRAPHIC EMULSIONS AND DEVELOPER

To extend their shelf life, unexposed holographic plates and film and prepared JD-2 developer solutions can be stored in a refrigerator when not in use. The container of unexposed holographic plates should be sealed with duct or electrical tape so that no

moisture can seep in. For film sheets, wrap the film package with kitchen plastic wrap, or place it in a reasonably air-tight plastic bag. Plates and film should be allowed to reach room temperature before opening in order to prevent condensation. Keep from children. Always label packages clearly as poisonous materials not to be consumed.

Read more:http://www.integraf.com/jd-2_holography_developer.htm#ixzz1ldaXXpxP

How to Use JD-4Holography Developer and Processing Kit

Copyright © 2007. IntegrafLLC. All rights reserved.

The instructions below are based on articles written byTung. H. Jeong, Riley Aumiller, Raymond Ro, and Jeff Blyth

JD-4 HOLOGRAPHY PROCESSING KIT

The JD-4 holography developer and processing kit provides all the chemicals needed for making holograms using Slavich PFG-03M or ColourHolographics "BB" holographic emulsions (for PFG-01 and VRP emulsions, useJD-2). Simply mix the dry chemicals in the JD-4 kit with water to create the developer components and bleach solution. This article explains step-by-step how to do this and use the JD-4 holography processing kit to make holograms.

Important NoticeThe following instructions for using the JD-4 holography processing kit have been modified from the actual instructions found in each package of JD-4. Instructions provided in this article are for your convenience only. For your safety and thorough understanding of JD-4, you should rely on the instructions and chemical safety notices that come inside each package of JD-4. Download .pdf file now (92KB).

Like many common household cleaners, JD-4 contains chemicals and should be treated with respect. Please read all the warning labels on each package. It is good practice to use eye goggles, dust mask, apron and rubber gloves when mixing chemicals. While the chemical solutions have low volatility, working in a ventilated area is recommended. You can download a copy of the MSDS for JD-4 holography processing kit from this website.

MIXING THE STOCK SOLUTIONS

The chemicals in this JD-4 kit are used to prepare approximately 1000ml of each of three solutions. You will need to add de-ionized or distilled water, which can be purchased at your local grocery store. It is best to use distilled water that contains no other chemicals although distilled drinking water, which sometimes contains small but negligible amounts of other chemicals, can also be used. Water from your tap generally contains fluoride and other impurities that may reduce the quality of your hologram. For efficiency and safety, teachers or an adult should pre-mix the solutions.

Part A Solution(1000ml)

CHEMICAL AMOUNT

Metol or Elon (p-Methylaminophenol sulfate) 4 grams

Ascorbic Acid (powder) 25 grams


Part B Solution(1000ml)

CHEMICAL AMOUNT

Sodium Carbonate, Anhydrous 70 grams

Sodium Hydroxide 15 grams


Bleach Solution(1000ml)

CHEMICAL AMOUNT

Copper Sulfate, Pentahydrate 35 grams

Potassium Bromide 100 grams

Sodium Bisulfate, Monohydrate 5 grams


Use three 1 liter (or larger) size clean glass or plastic bottles with leak-proof caps. Label themPart A, Part B,andBleachrespectively. To help dissolve the chemicals, you can heat the water until it is luke warm. Optionally, you can also prepare each solution in a clean beaker and then pour the solution into the bottle.

PART A. Fill the bottle marked Part A with roughly 1000 ml of warm distilled water. Dissolve the metol in it. Then add the ascorbic acid. Tightly cap the bottle. Part A will oxidize if it is exposed to oxygen. In time (over a few weeks to a few months), the solution may turn yellow due to the oxidation of the ascorbic acid – the solution is still usable. Once the solution turns dark brown, the potency is lost and it must be discarded.

Holography Tip

To extend the shelf life of Part A, protect it from oxidation. To do so, subdivide the solution into smaller bottles so that the unused portions are in full-capped bottles, with little or no air space. For example, try preparing two 500ml bottles for Part A instead of one 1000ml bottle. Refrigeration also slows down oxidation. Do not refrigerate Part A with food to avoid possible mistaken identity as food. When stored appropriately, Part A can last for months. Note that once solutions A and B are mixed together, the resulting developer solutions lasts only several hours. So, don't mix A and B together until you are ready to make holograms.

PART B.Follow a similar procedure to mix Part B, dissolving each chemical one-by-one. You can add the sodium carbonate and sodium hydroxide in any order. This solution will keep for many months at room temperature. Refrigeration further increases its shelf-life.

BLEACH.Follow a similar procedure to mix the Bleach; again, dissolving each chemical one-by-one. This solution has a long shelf life without oxidation issues. Store it in a safe place away from food and children. This solution will keep for many months at room temperature and does not need refrigeration.

Store chemicals in a safe place away from food and children.

HOLOGRAM EXPOSURE

For detailed instructions on making holograms, please see our article“Simple Holography”. Before making your exposures, you should mix and prepare your chemicals as follows.

PREPARATION


Your pre-mixed JD-4 Part A, Part B and Bleach Solution. 1 additional gallon (4 liters) of distilled or de-ionized water for best results. Tap

water may also work, but not as well. Avoid hard water. 2 small glass or plastic trays, just large enough so that the hologram you are

making can be submerged in a horizontal position. 2 large glass or plastic trays to hold 1 liter of distilled water for rinsing. Tap

water may also work. 1 large tray (optional, but recommended) to hold 1 liter of distilled water

mixed with about 1 ml of photographic wetting agent such as PhotoFlo. You can also use a small tray with less wetting agent, but you should replace the solution after a few holograms.

1 rubber gloveNow label one small tray as Developer A&B. Then, mix equal portions of Part A and Part B, enough so that the hologram to be developed can be totally submerged. Once mixed, the combined A&B solution can be used to develop several holograms, and lasts several hours.

Next to the developer tray place a large tray with one liter of distilled water. This will be used as a rinse.

Next, label another small tray as Bleach. Put enough bleach into it so that the hologram can be totally submerged.

Next to the bleach place another large tray with one liter of distilled water. This will be used as a rinse.

Optionally, place a large tray with the wetting solution in 1 liter of distilled water. Using a wetting solution is optional but recommended. It allows the hologram to dry evenly, thus helping you prevent smudges or streaks.

Check the order of the trays: developer A&B, rinse, bleach, rinse, wetting solution.

Presoak >>Developer

A&B>> Rinse >> Bleach >> Rinse >>

WettingSolution

PROCESSING PROCEDURES

After the holographic plate is exposed, hold it by the edges with your glove hand (or tongs). Keep the emulsion (sticky) side facing upwards to protect the emulsion from accidentally scraping the bottom of your developer tray. Holographic plates should be developed at room temperature.

1. Presoak:Presoak the exposed holographic film plate in distilled water for 10-20 seconds. 2. Develop:Quickly submerge the plate into the developer so that all parts get wet evenly. Slush it around for about 10 seconds. The hologram should turn almost black. 3. Rinse:

Rinse the developed hologram with agitation for at least 20 seconds. For best results and longer lasting holograms, rinse up to 3 minutes to make help ensure that all of Part A has been rinsed off. 4. Bleach: Place the rinsed hologram into the bleaching solution; agitate it until the plate is completely clear (this may take up to 1 minute); bleach for another 10 seconds. 5. Rinse again:Rinse the bleached hologram with agitation for at least 20 seconds (up to 3 minutes). 6. Finish in wetting solution:Optionally, place the finished hologram in this solution for about 20 seconds. Then, remove the hologram to dry. For best results, avoid streaks or runs as you remove the hologram from the solution.

Holography Tip

After bleaching, the hologram is safe to process with the lights turned on. This allows you to observe if your wetting solution has been evenly distributed on the hologram and if there are any runs or streaks. Hold the holographic plate from the sides to avoid potential dripping of solution from your fingers down the hologram.

The hologram is finished except for drying. A good way to dry the hologram is to stand it against a vertical surface with the bottom edge resting on a hand-towel or tissue paper. Best results are obtained when it dries naturally in clean, dust-free air. However, if time is limited, the hologram can be quick-dried by holding it vertically and blowing warm air across it with a hair dryer.

For a reflection hologram, the image can be viewed after thorough drying, using the laser light that exposed it or an incandescent spotlight. Thorough drying may take minutes to hours, depending on ambient conditions and technique. Transmission holograms, on the other hand, can be viewed with laser light even when wet.

STORING HOLOGRAPHIC EMULSIONS AND DEVELOPER

To extend their shelf life, unexposed holographic plates and prepared JD-4 developer solutions can be stored in a refrigerator when not in use. The container of unexposed holographic plates should be sealed with duct or electrical tape so that no moisture can seep in. Plates should be allowed to reach room temperature before opening in order to prevent condensation. Keep away from children and food. Always label packages clearly as poisonous materials not to be consumed.

Read more:http://www.integraf.com/jd-4_holography_developer.htm#ixzz1ldafIN67

How to Use Holographic FilmMinimize Movement with a Film Holder

By Alec Jeong and Dr. Tung H. Jeong

Copyright © 2003-2005. All rights reserved.

1. INTRODUCTION

We generally recommend first-time holographers use holographic plates instead of holographic film. That's because holographic film sheets can easily move during exposure. If the holographic film bends or moves even one thousandth of an inch during exposure, your hologram will not turn out. Instead, you will see gray blotches or irregular-shaped rings when you try to view the hologram. In more severe cases, your film sheet will come out completely gray.

The good news is that you can minimize such movement and thus still succeed in making satisfactory holograms with holographic film. For less experienced holographers, one such way for is by sandwiching the holographic film sheet between two glass plates.

2. CREATING A SIMPLE FILM HOLDER

When using holographic film sheets, it is critical that you ensure the film remains motionless during exposure. To do this, you can create a film holder. Simply sandwich the holographic film sheet between two plates of clear glass and then hold the plates together firmly with two metal spring-type clamps (ourBudget Holokitincludes these items). Though not a perfect solution for minimizing movement, it is the simplest way for beginners.

3. PROCEDURES

There are several important procedures you should follow when using holographic film sheets with your film holder. These are outlined below. As for the remaining steps such as setting up, exposing, and developing your hologram, these are similar to those used when working with holographic plates (see our article "Simple Holography"). Remove Air from Film HolderEven small amounts of air trapped next to the holographic film sheet can allow the film to move. Thus, we must remove pockets of air by squeezing the film tightly between the glass plates. You can use a pair of wooden blocks or flat hardbound books to press hard and evenly against the glass-film sandwich. Do so for 10 seconds or more.

Face Emulsion Side of Holographic Film Sheet Toward the Subject

The emulsion is the light-sensitive coating that is applied to the film backing material. For best results, face this emulsion side toward the subject of your hologram. This enables light to reach the emulsion without being degraded as it travels through the backing of the holographic film sheet. You can tell which side of the film has the emulsion because it feels sticky when touched by a most finger. Wait Five Minutes Before Exposing the FilmEven with the holographic film sandwiched in the film holder, the film (and the holder itself) may shift during exposure. Thus, for best results, wait approximately five minutes between the time you finish setting up your secured film holder and subject to the time you actually expose the film to the laser. This will allow both your holder and the film inside it to settle. Minimize VibrationIn exposing holographic film or plates, always plan ahead to minimize vibration around your lab and your emulsion, laser, and subject. Walking around your lab, loud sounds from a stereo, air flow from a vent, and even your breath are examples of things that cause vibrations that may ruin your hologram.

Read more:http://www.integraf.com/a-using_holographic_film.htm#ixzz1ldarWvcR

Viewing Your First HologramI failed to make a hologram . . . or did I?

By Alec Jeong

Copyright © 2004-2005 Integraf LLC

1. SUMMARY

If you can't see a holographic image after you've exposed and developed your film or plate, don't automatically think it's because you failed to make a hologram. It may be just the way you're viewing it.

2. INTRODUCTION

When my father Dr. Tung Jeong taught me how to make my first hologram 25 years ago for a science fair project, he also taught me not to jump to conclusions based on faulty assumptions (sounds like a scientist talking, eh?).

I had just completed all the steps to making a hologram per my father's expert guidance. I had chosen a solid object (a few coins), placed the object, laser, and film plate relatively safe from vibration, exposed the plate for about 10 seconds, and developed the plate under safelight. All said and done, when I went to view the plate I still could not find a 3-D image, let alone any image at all! The only thing I saw was one disappointing translucent piece of glass with some greenish tint on it. Crestfallen, I sighed, "Dad, I think I've failed. I must have messed up something in the process."

My father then took the plate into his hand. He tilted the plate a little bit the to left and right, then up and down, until he finally settled at a certain position. He then looked at me and said, "The image is right here!" To my amazement, there suspended in air before my eyes was a holographic 3-D image of my coins and quarters. So, I had not failed after all. Somehow, it was the way we viewed the hologram that made all the difference.

3. HOW TO OBSERVE THE IMAGE

Viewing Reflection HologramsTo view your hologram, you need an appropriate viewing angle and light source. With the appropriate light source, view the image by shining the spot light at the hologram from approximately the same angle you had the laser shoot when you were first exposing plate. You might need to tilt the plate left and right or forward and back to maximize the brightness of the image. It may take some practice. As for the light source, ideally, you want a bright spot light. Spot lights concentrate the light using a built-in reflector so that all the light is confined to the correct angle. Spot light are available at any K-Mart, Wal-Mart, and most other retail store. As a cheap substitute, you could also use a $1.98 (batteries included!) Rayovac pin light from K-Mart. In general, you cannot view a reflection hologram with a laser, fluorescent light, or light from a frosted bulb.

Viewing Transmission HologramsFor transmission holograms, the image is viewed using the laser light that exposed it. Reposition the hologram at the same location (and orientation) as that used during exposure. Allow the laser light to illuminate the hologram. Look through the hologram toward the location where the object was placed. The image you see should be exactly the same as the object. This is called the virtual image. Beginners should also try viewing the image by exposing the hologram with the laser beam head-on onto the plate. At this exposure angle, the viewing angle will shift minimally even if the emulsion shrinks during processing. After you get good at it, try a 45 degree angle; this is better for exhibition purposes when you can hang the hologram on a wall and illuminate it at 45 degrees with track-lighting from above. You can also project the “real image” (you can read about this in any high school physics textbook) onto the white screen. Simply replace the collimating lens onto the laser and adjust it until the laser becomes a “pointer”, i.e., focused into the smallest spot far away. Now shine the laser beams through the finished hologram in exactly the backward direction. Place a white card at the original location of the object and you will see the “real image."

Read more:http://www.integraf.com/a-viewing_holograms.htm#ixzz1ldb4rbc3

Making Holograms withStandard Laboratory Equipment

By T. H. Jeong andAlec JeongCopyright © 2003-2011

1. INTRODUCTION

In the article"Simple Holography"we lay out a process that allows you to make holograms not only as simply as possible, but also safely and economically for schools, young people, and hobby enthusiasts. The process require a basic set up using equipment and materials commonly found around your home.

The following memo below is an addendum to"Simple Holography". It provides you insight into making reflection holograms if you have access to standard laboratory equipment available in many schools.

2. SETTING UP THE LAB EQUIPMENT TO MAKE REFLECTION HOLOGRAMS

The photograph below shows you how to make use of standard equipments available in most school laboratories to make reflection holograms. The hardware needed are:

Lab stand Right-angle clamps Rod with a clothespin glued to it Small dish Computer mouse pad

As shown, the diode laser is held by the clothespin with the laser light directed downward. The object to be recorded (in this case, a figurine inside a small dish) is place on top of a computer mouse pad for vibration isolation. Arrange the laser and the object so that the illumination is as even as possible.

Below is a close up of the small dish.It is a convenient and stable method of making exposures if the laser is mounted on a lab stand with the light directed downwards.

Put some shiny and hard objects with details in a dish that are smaller than the plate.Now you are ready to make holograms.

2. STEPS FOR MAKING HOLOGRAMS

After you've placed the holographic plate over the small dish, let your set up settle for about 10 - 15 seconds. This helps ensure the plate is stable and won't move during the exposure.

With the room light turned off and a "safe light" (such as a night light) on, place cardboard between the laser and the object without touching either (fold the cardboard slightly so that it can stand on the table top alone). The cardboard serves as a shutter, like that found on a camera.

Now place a holographic plate, with the emulsion (sticky) side facing downward, on top of the object as shown below. The holographic plate must be resting on the solid rim of the dish so that there is no possibility of any movement.

Now lift up the cardboard carefully with the laser light is still blocked. Wait a couple seconds and then remove the cardboard quickly without bumping anything, and expose the holographic plate for 6 to 7 seconds. Then block the laser light again with the cardboard.

The hologram can now be developed with the process described in the article"Simple Holography".

For best results, remember to make sure the laser has been warmed up for at least 5 minutes before any holograms are exposed. Also, minimize any disturbance to the laser (do not touch it or even allow moving air to cross it) which may cause the outputs to become unstable.

Read more:http://www.integraf.com/a-holograms_w_lab_equipment.htm#ixzz1ldb9pZJl

Teaching Holography in ClassroomsMaking Holograms with PFG-03M Plates with JD-4

By T. H. Jeong, Riley Aumiller, Raymond Ro, (Lake Forest College)

and Jeff Blythe (University of Cambridge)Edited by Alec JeongCopyright © 2003-2005

ABSTRACT

This paper is useful for teaching holography workshops in classrooms as well as in makeshift locations such as museums, businesses, and homes. The target audience is very general, young children to adults of any profession, all of whom have no prior experience in making holograms. A typical number of participants is twenty-five, but can vary depending on space and personnel availability.

A central original contribution of this paper is the discovery of a new chemical processing regime for the Slavich PFG-03M holographic plates using what is now called the JD-4 developer kit. These silver halide plates have the highest resolution of its kind and some of the world’s best holograms have been recorded on it for several decades. Due to its low sensitivity and long developing time (12-15 minutes if using GP-2 developer, accompanied by natural drying), this material has historically been excluded from use in workshops.

Our new processing regime JARB (first letters of the authors’ last names) has makes PFG-03M possible for classroom use. JARB has the following advantages: It (1) increases the sensitivity of PFG-03M emulsion ten-fold without sacrificing resolution; (2) hardens the emulsion during processing without significant shrinkage; (3) has a ten- to twenty-second development time; (4) is quick drying using squeegee and warm air; and (5) allows the finished hologram to be

viewable with laser or incandescent light. Other advantages of JARB are (1) low toxicity, (2) low volatility, (3) non-staining, (4) low cost, and (5) long shelf life.

Keywords: holography, beginner holography, teaching holography, silver-halide processing, PFG-03M, JD-4

1. INTRODUCTION It has been well recognized that holography is a valuable subject for introducing young students to all the major topics of modern optics. These topics include light propagation, interference, diffraction, polarization, scattering, and photochemistry. Some of the major problems that prevent greater acceptance of holography in middle and high schools include expense, laser and chemical safety, lack of darkroom facilities, and time limitations in class and laboratory periods. Thee above problems are addressed in another article by the same authors entitled"Simple Holography". In this current article, we will see that PFG-03M with JD-4 developer (JARB) further minimizes these pracitical limitations.

PFG-03M has been used in Russia and elsewhere for making the highest quality exhibition holograms for several decades. One can simply develop such plates in one step using the GP-2 formula. However, this combination is not suitable for school use because of the following factors: (1) the sensitivity of PFG-03M is 1.5 millijoules per square centimeter (mJ/cm2); (2) the development time is 12 - 15 minutes; and (3) the holograms must be dried naturally by evaporation, which may require one hour or longer depending on the humidity.

These problems prevent schools from using PFG-03M with GP-2 because (1) the low sensitivity means lasers with greater outputs are needed, presenting an eye safety dilemma; (2) longer exposure time is required, presenting a mechanical stability problem; and (3) the time required for the hologram to dry exceeds the duration of a class or laboratory period.

The application of JARB on PFG-03M resolves all of these problems.

2. APPLICATION OF JARB (JD-4) ON PFG-03M

The discovery of using JARB for quick processing of holograms recorded on Slavich PFG-03M plates and film was made by Tung H.Jeong, RileyAumiller, RaymondRo, and JeffBlyth; thus it is called theJARB processing regime . Commercially, the chemical developer used is now called called JD-4.

JARB is ideal for making holograms during a lecture demonstration, or for laboratory exercises or workshops where many students must make holograms in a limited time. The advantage of JARB is that it effectively increases the sensitivity of PFG-03M ten times, from 1.50 to 0.15 millijoues/cm2. Thus the exposure time for holograms is one-tenth as long as when processed in GP-2. The typical development time is 20 seconds. Finally, drying time is drastically reduced by using warm air (from a hair dryer) because the JARB development hardens the emulsion. The total processing time using JARB can be as short as three minutes, from developing to drying!

The composition of JARB is a modified version of what was originally intended for processing “BB” plates manufactured in Germany (Birenheide, R., “The BB Emulsion Series: Current Standings and Future Developments”, SPIE Volume 3358: 28-30 (1997), ed.Jeong). It is mixed using three glass (or plastic) containers marked “A,” “B,” and “Bleach”, each with 1 liter of distilled or de-ionized water.Exercise extreme caution in labeling the bottles and keeping them out of the reach of children to prevent accidental ingestion of the contents).

Chemicals

Commercially, the chemical developer used is now called called JD-4, and contains the following.

Developer Part A--makes 1 liter solution Metol or Elon (p-Methylaminophenol

sulfate)-- 4g Ascorbic acid powder -- 25g

Developer Part B-- 1 liter Sodium carbonate, anhydrous--70g Sodium hydroxide-- 5g

Bleach-- 1 liter

Copper sulfate (pentahydrate)-- 35g Potassium bromide-- 100g Sodium hydrogen sulfate crystals-- 5g

Mixing instructions

1. Use three l liter (or larger)size clean glass or plastic bottles with leak proof caps. Label themA, B,andBleachrespectively.

2. Warm the distilled or de-ionized water to about 40oC (warm to the touch). 3. Fill the bottle marked A with 700 ml of warm water. Dissolve the Metol in it, then add

the ascorbic acid. Add 300 ml of warm water to make 1 liter of Part A developer. Tightly cap the bottle. Part A will oxidized if it is exposed to oxygen. In time (over a few days to few weeks), the solution may turn yellow due to the oxidation of ascorbic acid; the solution is still useable. Once the solution turns dark brown, the potency is lost and should be disposed.

4. One way of protecting it from oxidation is to subdivide the solution into smaller bottles so that the unused portions are in fully capped bottles, with little or no air space on top. Refrigeration also slows down oxidation (exercise extreme caution to prevent its mistaken identity as food).

5. Follow the same procedure for Part B (add the sodium carbonate and sodium hydroxide in either order). This solution will keep for many weeks.

6. Follow the same procedure for mixing the Bleach. This solution has very long shelf life.

Hologram exposure,

For detailed instructions on making reflection and transmission holograms, see the article"Simple Holography"on this website.

Using PFG-03M film or plate, expose the hologram so that each square centimeter area receives 0.15 to 0.4 millijoules of energy (there is batch-to-batch variation). For example, if a 5 milliwatt diode laser without a lens is location 40 cm from the plate, the exposure time is approximately 5 to 7 seconds.

Preparation before processing:


JD-4 parts A, B, and Bleach

1 gallon (4 liters) of distilled or de-ionized water 2 small glass or plastic trays, just large enough so that the hologram you are making

can be submerged in a horizontal position. Disposable weighing dishes are recommended.For processing 2.5x2.5 inch plates, we recommend buying dishes from Cole-Parmer Instrument Company (), catalog number U-01018-14 hexagonal weigh dishes, 4 3/4" dia. x 7/8" dia.

2 large glass or plastic trays to hold 1 liter of distilled water for rinsing 1 large tray to hold 1 liter of distilled water mixed with about 1 cc of photographic

wetting agent, such as Photoflo (optional, but recommended). 1 rubber glove Label one small tray asdeveloper. Mix equal parts of A and B so that the hologram to be

developed can be totally submerged Next to thedevelopertray, place a tray with 1 liter of distilled water Next, label another small tray asbleach. Put enough bleach into it so that the hologram

can be totally submerged Next to thebleach, place another tray with 1 liter of distilled water Finally, place the tray with the wetting solution in 1 liter of distilled water

Let's review for a moment. So, we now have our "assembly line" of trays placed in the following order: developer, rinse, bleach, rinse, wetting agent. To view the finished holograms, we recommend an incandescent spot light.A good and inexpensive light is a Phillip 45 Watt “narrow spot” flood light that operates on 110 volts and sold in hardware stores. The best lamp is ESX(20MR16) run on a HATVS12-60WD transformer sold by lighting companies.

Processing procedure:

After the holographic plate is exposed, hold it by the edges with your gloved hand, with the emulsion side (sticky side) facing upward.

1. Development: Quickly submerge the plate into the developer so that all parts get wet evenly. Agitate it for about 10 to 20 seconds.The hologram should turn black (at least a density of 2, i.e. about 1% light is transmitted).

2. Rinse: Rinse the developed hologram in distilled water with agitation for about 20 seconds.

3. Bleaching: Place the rinsed hologram into the bleaching solution; agitate it until the plate is completely clear (this may take up to 1 minute); bleach for another 10 seconds.

4. Rinse. Rinse the bleached hologram in distilled water with agitation for about 20 seconds.

5. Wetting agent: Place thefinished hologram in this solution for about 20 seconds.

The hologram is finished except for drying. The best way to dry the hologram is to stand it against a vertical surface with the bottom edge resting on a hand-towel or tissue paper. Best results are obtained when it dries naturally in clean air. However, if time is limited, the hologram can be quick-dried by holding it vertically and blow warm air across it with a hair dryer. For a reflection hologram, the image can be viewed, after thorough drying, using the laser light that exposed it or an incandescent spotlight.

3. PRACTICAL CONSIDERATIONS FOR WORKSHOPS

In this section, we will present practical ways of setting up and operating workshops in makeshift locations using commonly available equipment.

“Darkroom” preparation and system setups

Ideally, the space used should be an interior room with no windows. When the lights are turned off, the room should be dark with the exception of light from existing exit signs. Several

night lights (5-Watts) can be plugged into electrical sockets to provide low ambient light. For every four or five students, there should be one setup as explained in"Simple Holography". The laser light from each setup must be shielded so that it will not reach into the vicinity of another setup. Also, when one setup is being used, the commotion and vibrations must not be transmitted to other setups. For this reason, each setup should occupy its own table.

If an interior room is not available, then all exterior windows need to be blocked by black plastic sheets, making certain that there is no fire code violation.

Layout for chemical processing

It is to be understood that the above information is like instructions for a theatrical stage play. A basic rehearsal is recommended with the students is recommended before you start.

Each student is given a pair of chemical eye protection glasses and one rubber glove. To prevent cross contamination of chemicals, each student should use a separate set of

disposable trays (weighing dishes) for processing chemicals, but share buckets of water for rinsing. However, water for rinsing after development must be separate from that after bleaching. If running water is available, it can be used for both.

Assuming 2.5x2.5 inch PFG-03M plates are used, only 60 cc (milli-liter) of A+B developer and the same quantity of bleach are needed for each hologram. Thus, before the workshop begins, the instructor can pour out as many trays of developer and bleach solutions as there are students.

Even in semi-darkness, the developer is seen as a clear liquid and the bleach is green; so there is no confusion.

After each hologram has gone through the chemical processing and is washed, the final two steps are soaking in a Photoflo solution (optional, but strongly advised) and drying. We recommend that this be done in an adjacent room, unless the main room is large enough that lights for viewing finished holograms are not interfering with the making of holograms.

To prevent dripping on the floor, each student is given a tray (or a disposable paper plate) when transporting the wet holograms from place to place.

The traffic jam usually occurs at the area where drying and viewing takes place. Here, one or more buckets of Photoflo solutions are provided. Ideally, each students can use another weighing dish with Photoflo to keep each hologram clean. After a 20-second soaking, the hologram can be held by the edge and blow-dried with warm air from a hair dryer. The only way to avoid the traffic jam is to provide many hair dryers and as many viewing lights.

4. SUMMARY

Assuming the reader has read"Simply Holography", he/she should practice privately the making of reflection holograms using the above additional guidelines. The next step is to make holograms in front of an audience. With the experience thus gained, workshops can be offered to a broad range audiences.

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Medical Applications of HolographyCopyright © 2005 Prakash Mehta. All Rights Reserved.

This article provides an summary of the numerous medical applications in use and development today. This article has been compiled and reproduced by Integraf with permission of the copyright holder, and contains edits to the original article as needed.

IndexHolographic TechniquesX-Ray HolographyEndoscopic HolographyInternal Hologram Recording EndoscopeExternal Hologram recording EndoscopeMultiplexed Holography For Medical TomographyHolographic Light-in-Flight Recording MethodHolography in OphthalmologyDiffractive Bifocal Intraocular LensHolography in DentistryHolography in OtologyStudy of Tympanic MembranesHolography in OrthopedicsSummary

Holographic Techniques<return to Index>Recent improvements in hologram recording techniques and the availability of tools for the interpretation of holographic interferograms and the success of holographic techniques in imaging through tissues, ophthalmology, dentistry, urology, otology, pathology, and orthopedics shows a strong promise for holography to emerge as a powerful tool for medical applications. Holographic 3D images of eyes and interferometric testing of human teeth and chest motion during respiration were carried out quite early.

Mostly the holographic interferometric techniques have been used for biomedical applications.

X-ray holography can be applied for imaging of internal parts of the body and living biological specimens with very high resolution without the need for sample preparation.

Endoscopic holography has opened up the possibility of noncontact high resolution 3D imaging and nondestructive measurements inside the natural cavities of internal organs.

Three dimensional images of biological specimens can be synthesised from a series of two dimensional radiological images using the techniques of holographic stereogram, holographic conical stereogram and multiplex hologram.

Holographic contour generation is useful for measurements for biomedical specimen.

X-Ray Holography<return to Index>X-ray holography has the potential of examining the samples in aqueous solution with very high resolution without the need for sample preparation that often results in structural alternations. A X-ray hologram with a resolution better than that of a detector can be obtained by Fourier transform holography with a zone plate. The X-ray beam from a selenium X-ray laser (wavelength =20 nm, pulse length 200ps, output power 500 kW) falls on a narrow band X-ray mirror (bandwidth 10% and reflectivity 25% at 20nm wavelength) which reduces the broadband X-ray background produced by the Se laser. The mirror is a substrate with a flatness and roughness of better than 2nm to preserve the coherence of the X-ray laser beam, and is coated with alternate 20 layers each of silicon and molybdenum to provide high X-ray reflectivity. The sample on illumination with the X-ray beam scatters in the forward direction and forms the object beam. The object beam interferes with the portions of the X-ray beam that miss the sample. The recorded hologram can be reconstructed optically.The x-ray resist polymethyl methacrylate has high resolution but it requires development and reconstruction.

If the source size is kept small to ensure spatial coherence and the diffraction pattern is enlarged by shadow projection, a moderate-resolution detector with a high quantum efficiency such as a backilluminated CCD camera can be used for recording the hologram, instead of polymethyl methacrylate. The reconstruction of such a hologram can be performed

numerically. The system would permit the observation in real-time, which would be useful for biological samples. A resolution of 1.3 um has been obtained by taking d=1.0 um and N=23 lines/mm, and using a backilluminated CCD camera for hologram recording. The resolution obtained was limited by the resolution of the source size(1 um). These experiments show the promise of real-time observation of holograms of living biological specimens.

Endoscopic Holography<return to Index>Endoscopic holography has potential of providing a powerful tool for non contact high resolution 3D imaging and nondestructive measurements inside natural cavities of human body or in any difficult to access environment. It combines the features of holography and endoscopy. The ability to record a 3D large focal depth and high resolution image of internal organs and tissues greatly enhances the detection capability. The holographic endoscopy is of two types. In the one form the hologram is recorded inside the endoscope, while the other form uses an external recording device.

Internal Hologram Recording Endoscope<return to Index>The internal hologram recording endoscope produces full three-dimensionality of the reconstructed image with parallax and a large focal depth. The endoscope requires a miniaturized holographic setup inside the instrument and records a reflection hologram. It mainly consists of three parts; a film cartridge, a diaphragm and a single mode optical fibre (core diameter 4um) cable. The three parts are assembled in three adjusTAbLE stainless steel or brass tubes. The film is placed at 10 to the normal to the endoscope. The holograms are viewed under a powerful microscope allowing for the observation of individual cells. Due to large hologram aperture, the image with a low speckle noise and high lateral resolution is obtained. A lateral resolution of 7 um has been obtained in the reconstructed image that shows that the technique can be used for cellular structure analysis and may even substitute biopsy in tumour diagnosis. Specific dyes can be used to enhance the contrast of the tissue before recording the holograms as has been used extensively in gynecology and gastrointestinal tract.

External Hologram Recording Endoscope<return to Index>In the external hologram recording endoscope, a conventional endoscope is used. The system records the hologram outside the endoscope using an external reference beam. An endoscope with extremely small outer diameter can be used but this results in a loss of parallax and a small entrance pupil which produces speckles in the reconstructed image. However image plane holograms can be recorded to reconstruct the image without speckles. In order to obtain a high signal-to-noise ratio, the holographic endoscope must use gradient-index (GRIN) rod lenses. The speckle noise is reduced by illuminating and imaging the object by the same GRIN lens. An electro-optic crystal can be used as the photographic storage device in the holographic endoscope to provide in-situ recording, reconstruction, and erasure. These will make a new class of medical instruments for use not only in medical diagnostics but also in industrial testing.

Holographic endoscope can be attached to a salpingoscope for fallopian tube investigations or to otoscope for the inspection of outer and middle ear via an acoustic system to generate vibrations of the tympanic membrane . Holographic endoscope has been used with success for early recognition of cancerous indurations in the wall of urinary bladder.

Multiplexed Holography for Medical Tomography<return to Index>Multiplexed holography can be used for complete display of three-dimensional tomographic medical data. It uses photographically scaled images of the objects for making the hologram. The technique thus provides a way to make hologram whose images are of a different size from the original object. A series of photographic transparencies are made, all of which ate used to make a multiple-exposure composit hologram. the reconstruction of the hologram produces the original object with a magnification equal to the scale factor of the transparencies. Holographic stereograms, known as Cross holograms uses multiangular views of the object. The method consists of three steps: data acquisition, image processing, and making of the stereogram.

Since the holographic stereogram retains only the horizontal parallax of the object, it is limited to those applications in which surfaces are important such as prostheses and craniofacial

surgery. Moreover, most biological data such as CT or MR scans are generally collected as serial scans rather than multiangular views, multiplexed holography that reconstructs the image with all the sections at correct depths (locations) and both horizontal and vertical parallaxes is more useful.

Multiplexed holograms which retains full parallax and physical depths cues are known as volumetric multiplexed holograms, or multiplane-multiplexed holograms.

A volumetric multiplexed hologram is made from a stack of images such as a CT or MR scan. The first image in the stack is projected onto a screen placed in front of a holographic film. A hologram of this image is recorded by adding a reference beam. Next the screen is moved a few millimeters away from the holographic film and the second image in the stack is projected onto the screen, and a second exposure is made on the first one. All the images are similarly recorded, each at slightly greater distance than its predecessor. The film is then developed. When the hologram is reconstructed, it shows all the slices distributed in the three-dimensional space at different distances. Dispersion compensation techniques can be employed for making the multiplexed hologram so that the image can be viewed by a white light source.

The process of volumetric holographic multiplexing is similar to that of "inverse tomography" in which the projection screen mimics the tomographic slicing mechanisms, and the screen's gradual displacements mimics the patient's's linear translation through the scanner. Since the volumetric multiplexed hologram uses serial sections at different Z coordinates in space, it can be termed as 'zeta multiplexed hologram'. in contrast to a holographic stereogram which is known as 'theta multiplexed hologram' because it involves images at different angles.

It may be pointed out that the volumetric multiplexed hologram faithfully reconstructs complete information including physical depth cues and all of the grey-scale tonality in every slice without geometric or photometric distortion. the success of the technique, however, depends on the accuracy in ALIGNment of the serial sections in different exposures.

The complete system for producing and display of clinically useful multiplexed hologram can be automated.

Holographic Light-in-Flight Recording Method<return to Index>The holographic technique of light-in-flight recording can be effectively adapted for implementing first-arriving light principle for imaging through human tissue. The holographic method permits the use of both continuos and pulsed lasers with short coherence length. A short coherence length in holography is equivalent to a short pulse. Holography permits a gate that is as short as the pulse itself . A short-pulse laser beam is split into object beam and reference beam. The object beam passes through the tissue, and the reference beam is delayed so that it arrives at the recording plate in coincidence with the first-arriving light. Thus only the first-arriving light is recorded as a hologram. In practice, the reference beam is incident at a large angle to the recording plate, so that it arrives at different parts of the plate at different times. A part of the hologram would record the first-arriving light and the later-arriving light would be recorded at the other parts.

Holography in Ophthalmology<return to Index>Recording of a three dimensional image of the eye was one of the earliest applications of holography in the field of ophthalmology. Any retinal detachment or intraocular foreign body can be detected. Holography can also be applied for the measurement of corneal topography and crystalline lens changes and for the study of surface characteristics of both the nerve head and the cornea. Current methods of determining the shape of the central surface miss the central part and its periphery. The major advantage of holographic technique is the ultra high precision (sub-um range) with which such measurements are possible. The elastic expansion of the cornea can also be measured by holographic interferometry. This information is vital for corneal surgery. The expansion of the cornea of fresh enucleated bovine eyes has been examined as a result of a small increase in intraocular pressure using double exposure holographic interferometry. Their first investigations have revealed that each bovine cornea has its own typical expansion. The studies made so far show that holography has potential to investigate corneal endothermal morphology, changes on the cornea, crystalline lens changes,

and surface characteristics of both the nerve head and the retina.

Diffractive Bifocal Intraocular Lens<return to Index>A very useful application of diffractive optics is in the correction of refractive errors for old persons who have been operated for cataract by the use of a bifocal intraocular lens. Such persons have difficulty in changing the focus of their eyes for near distant and far distant objects. bifocal lenses are implanted in place of the natural eye lenses. The bifocal lens is a combination of a conventional refractive lens and a diffractive lens, the former focussed to infinity and the later for near distance vision. The efficiency of the diffractive lens is set at 50%, thus both the near and the far foci are accommodated over the whole visual field. The diffractive lens is fabricated on the rear of the conventional lens. When the eyes are focussed for a distant object, a blurred image is superimposed due to the presence of diffractive lens and vice versa, which obviously reduces the image quality. In most cases, the blurred image is discarded by the human visual perception and retinal processing system.

It is possible to place an ultra-thin (5 to 10 um) diffractive lens directly on the eye's cornea, where natural tissue growth over it would secure it, creating a semitransparent contact lens that would provide full visual ability.

Holography in Dentistry<return to Index>Both continuous wave and pulse laser holography have been used for applications of holography in dentistry.

The holograms offer a convenient way of storing toothprints, i.e. dental records of the casts of upper and lower centitions for legal and forensic purpose.

Holograms can be used for storing orthodontic study models that can be retrieved by a laser beam or a white light source for accurate 3D measurements. This saves a lot of storage space.

The holographic images are clinically reliable and random errors are not clinically significant. by studying the old and new records, orthodontists can watch the progress of their patients.

Holograms can be employed as training aids in the disciplines of dental anatomy and operative dentistry.

Holographic interferometry has been used for the contactless measurement of in-vivo tooth mobility and its movement in three dimensions, and measurement of dimensional changes of the tissue bearing surfaces of maxillary full dentures due to deformation of dentures material by oral fluids.

Holographic contouring technique can reveal the topography of teeth.

Holography in Otology<return to Index>The human ear is embedded in temporal bone that forms part of the skull base. The ear may be broadly divided into three parts: the outer ear, the middle ear and the inner ear. The outer ear consists of pinna (not shown in the figure), the external auditory canal and the tympanic membrane. The tympanic membrane is the inlet of the middle ear, which transmits the sound coming from the outer ear to the inner ear through auditory ossicles viz. malleus, incus and stapes. The middle ear is located within the tympanic cavity and contains a chain of auditory ossicles. The inner ear is the cochlea that has a coil like shape. The cochlea is separated into two parallel canals by basilar membrane. The receptor cells for hearing sense are spatially distributed on the basilar membrane.

Double exposure and time-average holographic interferometric techniques are powerful for studying different parts of the human peripheral hearing organ.

The vibration behaviour of models of the inner ear parts such as unrolled cochlea and coiled basilar membrane have been studied by time-average holography.

Time-average holographic interferometry has also been used for the study of vibration analysis of incudo-mallar joint with forces applied to the middle ear muscles has demonstrated that the incus and malleus move like a lever around a frequency dependent axis.

Study of Tympanic Membrane<return to Index>The tympanic membrane is important in coupling the acoustic sound pressure in the outer ear canal to the motion of the middle ear ossicles. Holographic contouring techniques may be applied for precise measurement of the shape of the tympanic membrane. When sound waves fall on the tympanic membrane in the outer ear, it vibrates. These vibrations are transmitted by the leverage action of the auditory ossicles to the stapes footplate attached to the annular ligament and finally to the fluid system of the inner ear. The vibrations propagate through the lymphatic fluid in the cochlea and cause basilar membrane to vibrate which in turn cause stimulation of the receptor cells on the cochlea. In order to use holography as a clinical tool for living persons, special care is required with regard to the optical system due to the difficult optical access through the narrow and curved outer ear canal. The device is made flexible by using a endoscope fibre bundle for the object illumination and using a thermoplastic film for recording the hologram. The device produces the results in 10 seconds, therefore is useful for routine clinical applications for quick study of the vibration pattern of tympanic membrane.

The holographic time-average interferometry is particularly suitable in studying the modes of vibration of the eardrum of living human as the modes of vibration are observed simultaneously over the whole area.

Many infants and old persons develop severe otitis media with effusion causing the malfunction of the eustachian tube leading to medial recess of the tympanic membrane under the compression of atmospheric pressure. This results in hearing loss, ear obstruction sensation, autophony, etc.

The time-average holography of a fresh human temporal bone sample has revealed a small tilt movement with a piston like oscillation of stapes . The vibration patterns of macerated human skull using time-average holographic interferometry has thrown light on the mechanism of sound transmission of sound transmission by bone conduction. The sample was excited by bone conduction vibrator.

Hearing impairments occur when micro-fractures of petrous pyramids in the human skull base are created by accidents. Double-exposure holographic interferometry has been applied for the study of deformation of the human skull under different load conditions to investigate petrous pyramids.

Holography in Orthopedics<return to Index>Holography offers an excellent tool for the contactless study of orthopedic structures, specifically external fixtures to reveal and measure strains on fixation pins and rods. Such studies are important in osteosynthesis with external fixture used for long bone fractures, to prevent dislocations of both fractured ends that are mainly caused by decrease in strength of the fixation pins. Dry bonein cantilever bending mode has also been studied by heterodyne holographic interferometry to determine the piezoelectric coefficients of bone.

Summary<return to Index>Holographic interferometric techniques have been widely applied with success for the study of different parts of human body including cornea, tooth mobility, tympanic membrane, basilar membrane, cochlea, temporal bone, incudo-mallar joint, chest, stull, and bones. Endoscopic holography is a powerful tool for non contact high resolution imaging and nondestructive measurements inside the natural cavities of human internal organs. X-ray holography has shown the promise of real-time observation of living biological specimens.

Copyright © 2005 Prakash Mehta,www.hololight.net. All Rights Reserved

20

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A Non-Silver Manual: Gum bichromateShare

Writer / Sarah van Keuren

The chapter called “Gum bichromate” of Sarah Van Keuren’s book “A Non-Silver Manual: Cyanotype, Vandyke Brown, Palladium & Gum Bichromate with instructions for making light-resists including pinhole photography”.

Read the previous section of this book.

Gum bichromate is the most versatile and the most labor intensive process described in this manual. A gum

bichromate print can be made in almost any color or combination of colors. Once a gum print has dried after

development, it is tough and stable.

http://www.alternativephotography.com/wp/processes/platinum/a-non-silver-manual-palladium

http://addthis.com/bookmark.php?v=250&username=xa-4d2b47f81ddfbdce

The gum process is a fusion of painting, printmaking, and photography. A light-resist, the size of the final image, is

usually needed for contact-printing against gum emulsion. The resist functions as a printmaker’s matrix or a

photographer’s negative.

Gum emulsion is a combination of pigment, gum arabic, and orange light-sensitive chromium salts in aqueous

suspension. Usually a gum print is built up in layers of transparent or semi-transparent watercolor pigment. A layer of

pigmented emulsion is hardened onto a surface by the action of actinic light.

Since layers of gum emulsion are applied by hand with brushes of various sorts, gesture can be subtly (or not so

subtly) incorporated into the image. Right after a layer of gum emulsion has been developed in water, it can be

manipulated subtractively with a stream of water, or with brushes, or by other means. The surface of a completed,

dried gum print, with slightly raised matte highlights and retracted glossy shadows, is almost sculpted in a fine bas-

relief.

Approaches to Building an Image in Gum

Digital negatives print well in gum. Nowadays gum workers of ordinary means can produce digital CMYK negatives

which can be used to render watercolor approximations of the printing industry’s process colors. In this way you can

experience first hand the phenomenon of weak individual layers of emulsion accumulating to emerge as a full-bodied

gum print with a fairly realistic color approximation of the original.

CMYK separations are by no means the only way to make digital negatives. Different principles, derived from painting

and printmaking, can govern the creation of separations and the choice of pigments. In the mode of the printmaker, a

layer in Photoshop could be created for each gum layer, and a rough preview of the final gum print with its transparent

layers could be viewed on the monitor. Adjustments can be made by creating new digital negatives or masks in

response to how the gum print is evolving.

Using just one high-contrast negative, you can produce a gum bichromate image with a range of color by printing in

successive layers of color from the same negative and brushing away parts of each layer to reveal underlying colors.

For instance your first layer could be blue, parts of which you brush away. If red is the next layer, it would print red

where the blue was brushed away and as brown on top of the blue; and blue would show in places where you brushed

away the red. A third layer of color manipulated this way, would dramatically extend the palette of the print. And if you

did not register the layers perfectly, ribbons of color could wrap around your hard-edged forms.

If a 21-step film scale of densities from to clear to opaque is contact-printed against a patch of gum bichromate

emulsion, you will see, after development, that there is gradation or separation of watercolor values in only about 5 of

the 2l steps. Below the most saturated of those 5 steps there may appear to be a stepwise darkening but that is a

printing-out effect that is caused by the overexposure of dichromate showing through the adhered pigmented gum.

The amount of pigment in the gum is finite and must be transparent enough to allow actinic light to penetrate and

attach it to paper. The pigmented emulsion in highlights, above what hardened enough to adhere to the paper, may

have hardened somewhat on the surface but not enough to hold onto the paper so it sloughs off entirely during

development in water.

Using just one continuous-tone (as opposed to high-contrast) negative, one dark color such as lamp black can be

printed repeatedly, each layer receiving a different amount of exposure, to produce a monochromatic image with a

long tonal range. Each layer of black will print in the shadows creating a black of unsurpassed depth, a few layers will

receive enough exposure to print into the mid-tones and only one or two layers will be exposed long enough to print

into the highlight areas.

Another approach is to ‘place’ different colors by varying exposure times through the continuous-tone negative. One

color is given only enough exposure to adhere in shadow areas; another color gets enough exposure to adhere in the

mid-tones; still another color gets exposed all the way into the highlight densities. A potential drawback of this

approach is that every color adheres in the shadow areas while it is being exposed to print into mid-tones and

highlights. For instance a blue layer exposed just enough to land in shadow areas will change to green if a yellow layer

is then applied and exposed to print into highlight areas. This problem can be solved by masking which will be

discussed later in this chapter.

For those who like to draw, handmade light-resists, such as drawings and washes on tracing paper or cliché-verre, print

well in gum, especially if additions and deletions are made on different layers of emulsion.

Photograms work well in gum. Objects can be 3-dimensional or flat, opaque or translucent. Photogram objects can be

added, taken away or moved during the exposure of each layer of emulsion.

If you are at heart a painter, you can do away with light-resists, partially or altogether, and simply paint with the

sensitized colors. When the paper is exposed to actinic light, washed, and dried, that layer will not be disturbed as new

layers are painted on top. Sensitized watercolor can be handled in this way like glazes of oil paint.

Brief History

Chromium, a relatively rare gray metal, was not identified as an element until 1797. It was given the name for color,

‘chroma’, because the varied colors of its compounds were used for dyes and pigments. The light-sensitive properties

of dichromates, including their ability to harden pigment mixed in colloidal gum arabic onto paper, were known by the

1850s but the gum bichromate process was not taken up in the early years of photography when the main role of the

camera was to record and document. It wasn’t until the 1890s that gum, with its atmospheric, autographic qualities,

was used seriously by photographers who sought to bring the medium into the realm of fine art. A show of gum prints

in the 1894 London Photographic Salon by the French photographer, Robert DeMachy, and the English photographer,

Alfred Maskell, influenced the revival of the gum bichromate process. DeMachy’s gum prints in red evoked sanguine

drawings by the Old Masters and his gum prints in black on laid paper seemed like drawings by Toulouse-Lautrec or

Georges Seurat. Almost immediately the gum process was taken up by Edward Steichen, and Gertrude Käsebier, both

Americans, and by Heinrich Kühn, an Austrian physician— to name just three of the artists.

Steichen, a native of Michigan, was traveling to Paris in 1894 to study painting. He stopped in London on the way and

was deeply influenced by DeMachy’s and Maskell’s gum prints. Steichen changed his first name from Edward to

Edouard when he arrived in Paris, took up photography, and found the expressivity of painting within the gum process.

He deepened shadows and imparted atmospheric color to some of his platinum prints with the addition of a layer or

two of gum. Other prints he built up entirely of gum manipulated with visible brushstrokes, as in his series on the

sculptor Rodin. Profoundly dark masses are in thrilling contrast to sculpted highlights. Explicit detail would be

distracting in these prints.

Gertrude Käsebier made gum prints in black on laid paper that look like spontaneous sketches in charcoal. In the

collection at the George Eastman House in Rochester, NY, there is a brown gum print of a woman in an interior. The

windows are ‘blown out’ and she didn’t hesitate to loosely draw, in brown pencil, the sheer curtains that didn’t print.

Heinrich Kühn and other Austrian and German photographers made large gum prints on rough watercolor paper. Their

handling seemed to derive from the lithographic tradition. Indeed, many lithographers (including myself much later on)

turned from the lithographic stone to the gum bichromate process not just to escape solvent fumes but to enjoy the

plasticity of the medium. Kühn took advantage of this to suit his compositional needs. I discovered his alteration by

lifting the mat of a gum print of his at Eastman House and seeing that treetops were taller in the image area that was

hidden by the mat than in the part of the image that was meant to be seen. Either he opaqued his negative (as

Steichen often did) or brushed away the gum rendition of treetops. By whatever means, he bent reality for his artistic

purposes.

World War I ended the golden age of pictorialism in which photographers saw themselves as fine artists, and gum

printing fell out of favor. Edouard Steichen became Edward again and abandoned gum to work as a Naval

photographer. After the war he became a famous fashion photographer and later, after World War II, he curated the

Family of Man exhibition of photographs at the Museum of Modern Art. This exhibit influenced many young

photographers in the 1950s (including myself at age twelve — it was the first photography book that I purchased).

Kodak reigned supreme until the late 1960s and early 70s when photographers in the Rochester area, tiring of

manufactured photographic papers and longing for the mark of the human hand, began researching 19th century non-

silver processes at Eastman House where the notebooks of earlier gum printers were available for study. Betty Hahn,

Bea Nettles, Robert Fichter, Judith Harold Steinhauser and Patricia Dreher were some of the pioneers in the revival of

non-silver processes in upstate New York.

Meanwhile, Lois M. Johnson, then a graduate student in Printmaking at the University of Wisconsin in Madison, saw a

cliché-verre gum bichromate print by Camille Corot and was inspired to research and experiment with the gum

process. Lois came East to join the faculty of the Printmaking Department of the Philadelphia College of Art (later to

become The University of the Arts). She taught a class called ‘PhotoMedia’ in 1973 that introduced gum bichromate as

well as cyanotype along with photo-screenprinting, photo-etching and photo-lithography. Patricia Dreher had moved

recently from Buffalo to the Philadelphia area and we signed up together for Lois’s innovative class. Patricia taught me

the vandyke brown process in the mid-70s. Later, Jerome Kaplan, chairman of Printmaking at PCA back then, invented

a brownish-black light-resist that he brushed onto vellum and scratched into. He then printed from the vellum in gum

and vandyke, processes that he too had learned from Lois Johnson and Patricia Dreher.

During the same time artist Phil Simkin had us all working to assemble pinhole cameras for a project at the

Philadelphia Museum of Art (see ‘Pinhole Photography’). This initiated my interest in pinhole photography which was

further stimulated when I met Eric Renner, pinhole guru and founder of the Pinhole Journal at a conference of the

Society for Photographic Education in Baltimore in the early 80s. Eric and I taught together at Tyler School of Art one

summer in the late 80s. He taught the pinhole part and I taught how to print from pinhole negatives in cyanotype and

gum.

Also in the early 80s Tom Davies, co-founder of The Photography Place in Philadelphia, gave an influential workshop on

daguerreotype called ‘Time Warp’. A few months later, Tom Shillea, recently arrived in Philadelphia from RIT,

demonstrated platinum/palladium printing at The Photography Place and later at PCA.

Judith Harold Steinhauser became an influence in the Philadelphia area when she arrived to teach at Moore College of

Art. Her gum prints seemed to deconstruct the medium. Her loose brushstrokes revealed how one layer of color applied

over another created a third color.

Martha Madigan of Tyler School of Art made huge cyanotype photograms on rolls of BFK Rives paper. Later she worked

with photograms on silver chloride printing-out-paper which is about as light sensitive as gum bichromate emulsion.

Catherine Jansen of Bucks County Community College created an entire room out of figures and objects printed in

cyanotype on cloth. Book artist, Enid Mark, learned cyanotype and vandyke and incorporated those processes into her

books. Although these artists did not print in gum, their work had some of the same roots.

Alida Fish, known already for her gum bichromate prints, came to the Philadelphia College of Art in the late 70s and

after a while Jeannie Pearce, also known for her work in gum, arrived at PCA. Twenty years later, both Jeannie and Alida

were pioneers in digital imaging at what was by then UArts.

In the 80s and 90s, newspaper photographer Don Camp created enormous casein portraits from lith film using soil as

pigment mixed with milk protein and dichromate. He taught casein printing to Rosae Reeder who was at the time a

graduate student in Book Arts/Printmaking at UArts (see Rosae’s chapter on ‘Casein Printing’).

Absorbing these influences, I began printing from pinhole negatives in cyanotype and gum bichromate. I combined the

two processes after seeing a show of cyanotype/gum prints by Tony Romano, now deceased, at the Philadelphia Art

Alliance around 1980. I liked the way the crisp intense blue of cyanotype in shadow areas looked under layers of black

and red gum. For 20 years I printed this way from pinhole negatives.

In recent years I have been printing, still in cyanotype and multiple gum layers, from desktop negatives created by

scanning and composing in layers from a single black-and-white pinhole negative, or collaging in layers from multiple

pinhole negatives. More recently, I have been using small files captured with a digital camera and printing somewhat

fragile CMYK separations onto cheap inkjet acetate. When I get a new printer with archival inks I will produce more

desktop negatives printed onto better inkjet films and vellums. Meantime I’m using a Scitex imagesetter at UArts that

produces smooth lith film digital negatives (in half-tones only), up to 18˝ x 24˝ in size, that cost less than what a

commercial lab would charge. At 200 lines per inch, the halftone pattern is scarcely visible to the naked eye in one

printed layer of gum and quite invisible if 4 CMYK layers are printed on top from 4 differently angled separations.

Ernestine Ruben, already well known for her platinum and pulp paper prints, is now working in gum and extending the

possibilities of the medium in a painterly manner. For several years she has been a guest critic for the advanced non-

silver students and a special mentor for a number of them. She told me about the online Alt Process List (see

“Resources”) which I joined and participated in for nearly two years. For me it was a graduate school in non-silver

processes from which I gained almost more information than I could absorb. It was great to read the emails of

participants from all over the world who brought their expertise from incredibly diverse backgrounds to bear on

alternative processes of all sorts. I had to leave the List, at least for now, to center on my own experience of gum and

other processes, and also simply to find the time to rewrite and expand this manual, but I recommend it as a forum on

alternative processes.

A new generation of gum printers from the Philadelphia area includes Mira Adornetto, Clare Amarakoon, Christopher

Dardaris, Sandra Davis, Karen Fiorito, Rebecca Gilbert, Stuart Goldstein, Melissa Good, Matt Hollerbush, Jahjehan Bath

Ives, Joe Ives, John Joyce, Karen Lefkovitz, Dana Leight, Martin Lennon, Dave McKenzie, Scott McMahon, Laurie Beck

Peterson, Rosae Reeder, Suzanne Solis, Lori Spencer and Evan Woldow. These artists, and others that I apologize for

neglecting to name, sustain and extend the revival of non-silver processes, and in particular of gum bichromate.

How it Works

In the gum bichromate process, watercolor pigment is blended with viscous gum arabic, sap of the acacia tree. The

resulting pigmented gum is combined, usually 1:1, with an orange solution of light-sensitive chromium salts. This

emulsion can be brushed onto the surface of paper that has been sized (see ‘To Size or Not to Size’ later in chapter),

without soaking into its fibers. This is in contrast to watery chemical solutions, like cyanotype, vandyke, and palladium,

that soak into paper or cloth and must lie in contact with organic fibers to reveal their full tonal range and intensity.

Gum emulsion can be applied to non-organic synthetic surfaces as long as the surface provides enough ‘tooth’ for it to

adhere in image areas. When an exposed gum print is submerged in water, the emulsion including the orange

chromium solution releases in highlight areas that were not exposed to actinic light and remains attached where

exposed to actinic light.

Minimally exposed areas, that received just enough actinic light to attach pigmented gum to the support, are soft and

vulnerable to marring until the print dries. The orange dichromate solution mostly washes out and these passages can

be deleted if desired with a spray of water or gentle brushing.

If any more than the minimum exposure is given through the negative, a printing out of the chromium salts, in tones

ranging from yellow/beige to a fairly dark brown, will begin to occur beneath or within the pigmented image. For some

reason this aspect of the gum process is seldom discussed. It is like an ochre under-painting and adds warmth and

depth to the gum image while skewing the watercolor hue. When exposed through a negative with a wide range of

densities, a single layer of gum can produce multiple hues in the developed print. For instance, a layer of emulsion

containing blue watercolor can range in hue from pure blue in areas that received just enough exposure to adhere the

emulsion to more heavily exposed areas in which the yellow/beige/brown printing-out of chromium salts turns the blue

into various shades of green.

While the print is still wet from development, the blue passages in the least exposed areas can be deleted, if desired,

with a spray of water. Mid-tone passages, in which the blue looks light green after development, received more than

the minimum exposure. Pigment in the mid-tones can be brushed off usually, but the embedded chromium salts, that

received exposure beyond the minimum needed to adhere the pigmented gum, will print out in shades of golden tan

that cannot be deleted manually. These tans can later be removed in a bath of sodium bisulfite, after the print has

dried and hardened overnight.

Shadow areas, that received the greatest amounts of actinic light, adhere, locking pigment onto the support, and

printing out, along with the pigment, to produce greenish brown hues. It is difficult to lift or manipulate gum colors that

http://www.alternativephotography.com/wp/books/a-non-silver-manual-resources

have received this much exposure. The darker tans, that print out in these open areas of the negative, can be changed

from brown to light gray/green during clearing in sodium bisulfite but do not vanish entirely.

A full-bodied image in gum is created, usually, with multiple layers of gum bichromate in varying hues and

concentrations that are exposed for varying amounts of time and developed with varying amounts of manipulation.

Unless the negative consists of entirely clear and entirely opaque film which can be given just enough exposure to

adhere the pigmented gum, there will be at least some printing-out of chromium salts in the more open parts of the

negative for each layer of emulsion.

Chromium Salts: Ammonium versus Potassium

A note of clarification: the words dichromate and bichromate are interchangeable. In this manual the nineteenth

century ‘bi’ prefix refers to the gum bichromate process in deference to the artists who first used the medium, but the

‘di’ prefix is used to refer to the chromium salt by itself and is what you will find in chemical catalogs today.

Ammonium dichromate and potassium dichromate both exhibit two important printmaking characteristics already

described: l) with exposure to actinic light they harden gum arabic with its cargo of pigment onto a support; 2) with

further exposure both chromium salts print-out in shades of tan within the adhered emulsion.

But there are some differences between these chromium salts. Ammonium dichromate is more soluble in water than

potassium dichromate which means that with a more concentrated solution exposures are quicker and more prints can

be made within a finite period of time. For that reason we have been using ammonium dichromate in class. However, if

you are working at home and using the sun as an actinic light source, the difference between a one minute exposure in

the sun using ammonium dichromate and a two minute exposure using potassium dichromate may be insignificant.

Ammonium dichromate, the more expensive of the two salts, is combustible and is shipped as a hazardous chemical

for an extra $25.00 within the U.S.; potassium dichromate (which was used more commonly in the past) is not

combustible and can be shipped in the conventional manner — although some suppliers don’t seem to know this.

As I said, we have been using ammonium dichromate. However, now there are additional actinic light sources in

Printmaking, so we will begin to use up an old 5 lb. jar of potassium dichromate powder that was given to us. I used it

last summer and although it may be 30 years old it worked fine.

Taking Precautions and Safeguarding Your Health

According to Overexposure: Health Hazards in Photography by Susan Shaw (published by The Friends of Photography,

1983), “Ammonium dichromate is moderately toxic by skin contact and by ingestion; it is highly toxic by inhalation.

Dichromates are also suspected carcinogens. Skin contact can cause irritation, allergies, and possible ulceration…”

Since 1983 it has been shown that dichromates are indeed carcinogenic. The liver cannot eliminate heavy metals such

as chromium. Chronic exposure to chromium salts through skin contact, inhalation or ingestion could eventually cause

liver cancer. Short of liver cancer, chronic exposure can induce asthma, other allergic reactions and skin ulcers. So,

handle the bright orange dichromate crystals and solutions of dichromate carefully, with adequate protection!

However, if you should get a few drops of dichromate solution on your skin, do not panic. Immediately wash the

exposed area thoroughly in cool running water. Usually it is repeated or prolonged skin contact that poses a problem.

If you should get dichromate in your eyes, flush them immediately and for several minutes with water (at school use

the eyewash fountain) and seek medical attention.

Launder contaminated clothing.

The dichromate is still ‘hazardous’ when you are registering negatives so avoid touching the dry sensitized emulsion.

But, once a print has been developed, thoroughly washed, and dried, whatever remains of the dichromate is locked

into the emulsion and the paper and no longer poses a hazard in handling the print.

If you are planning on working in gum at home (which means bringing chromium salts into your home), don’t prepare

your dichromate solution with containers or implements that may be used for cooking or eaten from in the future.

Don’t mix or apply dichromate in your kitchen. Label all bottles and jars with the name of the chemical, its

concentration when in solution, the date it was mixed and a warning. Don’t work with flammable ammonium

dichromate near an open flame. Don’t allow crystals to build up on the mouth of a dispenser because they could

crumble and then become airborne (this is true at school too). Wash and dry such surfaces. At home in my work area I

dispose of contaminated rags, paper towels, stirring sticks, etc. in a closed can lined with 2 recycled plastic grocery

bags, one inside the other. I carefully tie the outer bag closed on itself before it gets too full so that dust from dried

dichromate won’t escape in the face of anyone who handles the trash

Be sure to keep dichromate out of reach by children especially since they may be attracted to the bright orange

crystals or assume that the orange solution is a beverage.

If you must dispose of more than an ounce or two of dichromate solution, make certain it is clearly labeled and take it

to a hazardous waste pick-up point. Most communities have such pick-ups scheduled at least twice a year. But try not

to order and mix into solution more than you can imagine using. The dichromate crystals will keep in a sealed jar

indefinitely and in solution it remains potent for a number of years.

During the 25 years that I have been teaching non-silver processes, including gum printing, I am aware of nobody who

has been injured other than myself. Years ago, while helping students register negatives on their sensitized gum prints,

I must have gotten a bit of dichromate lodged under the cuticle of my little fingernail. I did not wash my hand

thoroughly and an abscess formed. Eventually I lost the fingernail. Although it did grow back, this incident made me

more respectful of potential hazards and the need to maintain fastidious work habits.

Chromatype

It is possible to make a print in delicate shades of tan (that may turn slightly gray/green over time) applying liquid

dichromate by itself to paper without pigmented gum. Somewhat warily, I call this a ‘chromatype’ based on this word’s

definition in my 1933 edition of Webster’s New International Dictionary in English: “A picture made upon paper

sensitized with potassium dichromate or some other chromium compound.” (It is possible that the expression

‘chromatype’ refers to all of the many processes — including gum, casein, carbon, photogravure, and the older

generations of photo-lithographic plates and screen-printing emulsion — that rely on the light sensitivity of chromium,

but I am interpreting the definition to mean dichromate used alone.)

Chromatype exposures need to be many times longer than for gum bichromate prints since you are making an image

out of the secondary underprinting that comes with overexposure of a gum print. Like cyanotype, vandyke, and

palladium, a chromatype image is formed around and within the organic fibers of paper by a watery chemical solution

(as opposed to within an emulsion on top of sized paper) which gives a fine but limited gradation of tone from yellow to

brown. Since usually dichromate solution is brushed onto un-sized paper, there is no curl from sizing or gum layers to

contend with. The negative should be hinged on one side with two pieces of clear tape, as is done for the iron

processes covered in this manual, so that exposure for a chromatype can be judged by inspection. The printed-out

image should look over-exposed since quite a bit of yellow/tan in the highlights will wash out during development in

water. If, on the other hand, the developed chromatype looks over-exposed it can be reduced by bleaching the print in

sodium bisulfite or its substitutes (see ‘Clearing a Gum Print’).

Gum Arabic

Tears of gum arabic (like tears of pine resin) are harvested from the thorny acacia tree in Arabia and North Africa by

Bedouin tribesmen. Burlap sacks of the rough bits of gum are delivered to processing centers where the gum is refined

into various forms and degrees of purity. In the past 30 years the price of gum arabic has risen from $3 a gallon for

lithographer’s gum arabic solution to nearly $30 a gallon as demand for it has increased and supply has dwindled due

to drought and other factors — such as elephants scratching their backs on the acacia trees and knocking them over.

One hundred years ago, a gum printer would suspend the unrefined amber pieces of gum in a cheesecloth bag in water

overnight. By morning the gum dissolved in water would have formed a syrupy liquid known as a ‘colloid’. Its specific

gravity should have been somewhere between 12˚ and 17˚ Baumé but I imagine that, as is true with experienced

cooks, the correct viscosity of the gum was achieved intuitively. A colloid is a viscous liquid whose particles stay in

suspension and do not sink to the bottom as sediment. Egg white (albumen), gelatin, and casein are also colloids that

have served as emulsions for dichromates, silver salts and other light-sensitive materials. The homemade colloidal gum

had to be used right away since, unlike maple syrup, it did not have much sugar to preserve it and, with its pH of about

5, was a suitable culture medium for micro-organisms. Today gum arabic is refined and hydrated to a viscosity of 14˚

Baumé for lithographic purposes. A strong preservative is necessary to keep it from going sour and although it is not

listed as an ingredient on gallon containers of gum arabic, I have heard that mercuric chloride, formaldehyde or thymol

is used as the preservative. As a lithographer I loved spreading the gum arabic on the stone or plate with my bare hand

but now I might wear a surgical glove. The gum arabic that is used in foods must have more benign preservatives such

as sugar.

One Coat versus Layers

The first time I printed on my own in complete gum bichromate emulsion, back in the late 1970s, I decided to make a

strong black image using a single exposure from a high contrast lith negative. (See chapter on “Making Enlarged

Negatives”.) I stirred quite a bit of powdered black pigment into 14˚ Baumé gum arabic, combined it 1:1 with a solution

of ammonium dichromate, and coated BFK Rives paper with the resultant opaque black layer of emulsion. To lock the

black onto the paper I exposed the contact frame, with my negative pressed against the sensitized paper, to midday

sun for half an hour — this is about 30 times more exposure than I would give today. To my surprise and

disappointment, the entire emulsion lifted off in the water. Eventually I understood that actinic light must be able to

penetrate the pigment to effect the chemical reaction that hardens pigmented gum and attaches it to paper. I had

coated with emulsion that had such a high concentration of black pigment that actinic light could not penetrate to

adhere the emulsion to the paper fiber. If the white of the printing paper is not visible beneath the emulsion, as if seen

through a color filter, an image usually cannot adhere and the emulsion sloughs off during development in water.

Occasionally, with the right combination of negative, pigment, and printing paper, a satisfying gum print is made with a

single coat of emulsion. Demachy is known to have printed some of his most famous gum prints that way, according to

Judy Seigel, editor of Post-Factory Photography, Issue #6, page 33 (see “Resources”). I encourage students learning

gum to bring any paper they want to print on in the beginning and to try pigments of all sorts. In my experience,

however, rich gum prints are usually built up on sized paper in increments, layer upon layer.

Two Part Emulsion: Pigmented Gum over Dichromate

When I introduce students to gum printing, we start out by making prints in chromatype (dichromate in solution by

itself) so that they understand the phenomenon that occurs in a gum print when exposure goes beyond hardening and

into tanning. Any kind of white paper with wet strength will do. Often the resultant print is quite appealing with delicate

golden tones ranging into browns and occasionally we get a ‘keeper’.

The next exercise builds on the chromatype and was inspired by an article in an old copy of Photo Miniature that Paul

Cava, Philadelphia art dealer and artist, lent to me decades ago. Unfortunately I did not record the name of the author

and nowhere else have I seen or read about this approach which permits an especially free use of gesture and color in

gum printing. Some of the non-silver students, especially Painting, Illustration, and Printmaking majors, choose to work

in this manner even after the complete emulsion has been introduced.

With the class gathered in the non-silver darkroom under tungsten light, I coat a taped-down sheet of un-sized BFK

Rives with ammonium dichromate, leaving white margins for safe handling. It is unnecessary to size the BFK Rives

used for this exercise.

On the coating table is a collection of pigments mixed with gum in little jars or plastic film cannisters. One by one each

student picks a pigmented gum color, stirs it with a stick of matboard (the pigment tends to settle on the bottom),

pours a small puddle of it onto the sensitized BFK and brushes it out with a dry 1˝ sponge brush in a patch or

arabesque on the paper. At first the paper is quite wet with deep yellow dichromate and the pigmented gum bleeds

like watercolor into it, but by the time the last students (in a group of 10-12) apply their areas of color, the dichromate

is nearly dry and the pigmented gum sits on top of it without spreading. Some students leave the pigmented gum

puddled while others brush it on thinly and overlap with other patches. There is usually an observation made on how


the color of the pigment is skewed by the deep yellow dichromate. When the paper is dry the students lay flat objects

and hand-drawn light-resists, as well as negatives and printed matter, upon the paper.

The ensemble is given a prolonged exposure in our platemaker, at least three times as long as might be used for a

complete emulsion in which pigmented gum and dichromate are mixed and applied together. This is because extra

time is needed for light to penetrate the upper layer of pigmented gum and adhere it to the dichromate and the paper.

Registration of the diverse light-resists would be lost by opening the platemaker to check underneath them for signs of

printing-out, and, in any case, the materials have such a wide range of densities that no single exposure would work for

all — hence the rough estimate of exposure time.

When the print has been exposed and removed from the platemaker, we note how the dichromate has darkened in the

areas that were not covered with pigmented gum or light-resist, and how tanning shows through the pigmented gum,

strengthening the rendition of light-resists but now affecting in a different way the hues of the watercolor pigment.

As the exposed print is slipped face up into a tray of water and gently rocked in the tray, the students have their first

view of unexposed pigmented gum and dichromate releasing from the BFK. It is usually a surprise for them to see that

heavy blobs of pigment are also sloughing off, even where they were given full exposure. This provides an opportunity

to explain that actinic light could not make it through the heavy pigment to adhere it to the dichromated paper.

Lifting the print with gloved hands and immersing it face down and then lifting it again and slipping it back in the tray

face up with unexposed pigment and dichromate streaming off the emerging image, it is usually apparent that blue

and violet passages have gotten more exposure and are adhering more than red, yellow or brown passages. This

demonstrates the fact that actinic light travels easily through blue and violet but has a harder time penetrating warm

colors that partially mask themselves. It also becomes evident that some light-resists were suited to the exposure time

and rendered well while others were so dense that only a white silhouette was recorded. Still other light-resists may

have been so thin that the renderings are quite filled in.

If the light-resist was underexposed and washes off there is nothing to do but recoat the paper and give a longer

exposure or find a more open light-resist. If the rendering is filled in from overexposure, subtractive manipulation often

can open up highlights and mid-tones.

It is a common mistake of students to begin brushing the surface of a gum print after it has been in water for only a

minute or so and then to be disappointed that detail they wanted is gone. Some of the subtlest, most beautiful gum

passages are lost by this harsh approach. But since beginning students tend to overexpose, this premature brushing

often becomes a way of working, for better or worse.

Manipulation of Gum Prints

Manipulation should be done in stages, beginning with the gentlest and ending with the harshest. After water

development image-side-down with some agitation from rocking the tray, and after carefully flipping the print face up

and face down without marring its soft surface, and after a final wash with a tray siphon, face down and face up until

yellow dichromate no longer drips from it, lay the wet print face up on a piece of plexi and gently direct a small stream

of cool water in a margin of the print, tilting the plexi so that water flows across the area you wish to open up or

manipulate. If nothing releases, aim the stream of water directly onto the targeted area. Next, increase the impact of

the stream of water by pouring it from higher up or squirting it under pressure through a hose. If there is still no

release, slowly bring up the temperature of the water. If even hot water has no effect, only then should you resort to

using a soft, wet 1˝ sponge brush or some other soft brush to lightly stroke the area you wish to brush away while

directing cool water onto the area. Next try a dry 1˝ sponge brush, which is more abrasive than a wet one, still flooding

the area with cool water. Raise the temperature of the water and strength of the spray. If still no release has occurred,

take a piece of wool etching blanket or the equivalent and gently rub it on the recalcitrant area. A last resort would be

to mix an alkali such as household bleach (sodium hypochlorite) or washing soda (sodium carbonate) with water in a

graduated cylinder, apply some with a sponge brush, allow it to sit for a minute or two, and then hose or brush the area

and see if the tough bonds of dichromate have been loosened (see upcoming section on ‘Gum Bichromate Solvents’).

Finally, after the print is completely dry, it can be cleared of as much of the tanning as possible (see next section) so

that the hues of the watercolors reveal themselves.

Clearing a Gum Print

If too much tanning has taken place in either a chromatype, or in a gum bichromate print (usually after several layers),

the offending golden/brown tones can be removed in a bath of approximately 5% sodium bisulfite (or sodium

metabisulfite – or even sodium sulfite) which, being a weak acid, also further sets and cures the image. A more

concentrated mix of the clearing agent can be applied locally and then washed off. It is important that the print be

completely dry since otherwise some of the pigmented gum that hasn’t hardened may release, damaging the print and

contaminating the clearing bath.

The sodium bisulfite bath should be mixed and used outdoors or under a fume hood because it smells bad and is very

irritating to the respiratory system. I dissolve about 2/3 of a cup of sodium bisulfite powder or crystals in a gallon of tap

water. (The exact strength of the solution is not critical since the clearing is judged by eye but it is best not to have it

so strong that its action cannot be halted quickly by slipping the print into a tray of plain water — or so weak that you

stand around waiting forever.) Sodium bisulfite crystals take longer to dissolve than its powdered form. The solution

can be reused to clear dried gum prints until it turns a pale blue/green at which time it should be discarded.

Keep a tray of water right next to the sodium bisulfite bath to stop its action in case only partial clearing of tans is

desired and also to remove some of the acidic clearing agent before putting the print in the final wash tray to remove

whatever remains. Dark brown tanning does not clear entirely but turns a pale gray/green which might make a gum

print cooler than intended.

Recently I learned from The Book of Alternative Photographic Processes by Christopher James (2nd Ed. Delmar, 2008),

a book that I highly recommend, that sodium sulfite, which we have on hand to clear the yellow out of palladium prints,

can be substituted for sodium bisulfite to clear gum prints. The concentration of sodium sulfite needs to be doubled, at

least, and the action is slower, but it is effective — and odorless!

Preshrinking

Stepping back to the beginning of the process, preshrinking your printing paper will give dimensional stability to a gum

print which it needs if it is going to be built up in registered layers. If you are not working with photographic duotone or

CMYK separations, close registration may not be an issue with your particular images and you can skip this discussion.

Sometimes the act of sizing with hot gelatin is equivalent to preshrinking the paper, at least for gum prints that are 5˝

x 7˝ or smaller. But for 8˝ x 10˝ prints and larger it may necessary to preshrink paper in a tray of very hot tap water for

about 10 minutes as you might do with clothes that you want to make smaller. It is possible to preshrink up to 12 or 16

quarter sheets of BFK in a 14˝ by 17˝ tray that is nearly full of hot water but the sheets must be lifted and interleaved

to eliminate air bubbles and to ensure that they are evenly wetted. Then hang each wet sheet by a corner from a

clothespin and rotate corners as drying proceeds to avoid distortion of the soft wet paper as you would do with laundry.

Judy Seigel told me that a 36 hour soak in room-temperature water is superior to a brief hot water soak for

preshrinking. I tried it and indeed paper soaked that way shrank a bit more than paper that was submerged in hot

water for much less time. So if you have the foresight, time, and space in which to do the long room-temperature soak,

you’ll be saving the fuel that’s consumed heating water — and getting a better result.

To Size or Not to Size

To be a successful gum printer you need to think empathetically about your materials and imagine action on a scale

that you can’t see with the naked eye. Picture yourself scaled down to the size of a dust mite on the surface of an un-

sized piece of BFK Rives, a soft printmaker’s paper. As a dust mite you will find yourself in a white undergrowth of

rough cotton fibers that can snag jagged flakes of watercolor pigment and not let go — even in areas that received no

exposure. This means that freckles of color (trapped pigment) sometimes remain where the print should have clear

white highlights. These dots of color may be acceptable and even desirable; but if you definitely want clear un-freckled

highlights, you need to apply a gluey substance called ‘sizing’ to coat the rough fiber enough so that pigment can

release. Imagine ice coating every fiber so that unexposed flakes of pigment can slip out of the smoothed, iced

underbrush and rise into the wash water. It may help in understanding the sizing issue to realize that flakes of pigment

are enormous compared to molecules of dichromate or iron salts and present a physical rather than a chemical

challenge.

To Size

BFK Rives is a French 100% cotton paper commonly used for etching and lithography. It is what Steichen and others

printed upon in gum over 100 years ago. The paper is very familiar to me as a printmaker. It is moderately priced and

commonly available at art supply stores. The fact that this paper is still being widely used gives me a sense of

continuity with the past, despite two World Wars and everything else that has occurred in the past 100 years…

Preparing to print, I look for the water mark that says ‘BFK Rives, France ∞’ in the lower left corner of a horizontal full

sheet of BFK (either 250 or 280 gram, one a little thinner than the other). On the side that is right reading, I put small

x’s with an HB pencil in the three corners that don’t have the water mark. This is to remind myself that this is the side I

wish to print on. I choose the right reading side because it is a little fuzzier and provides more ‘tooth’ for the emulsion

to adhere to, but either side will work with BFK (unlike some papers which are made to be printed on a specially coated

side).

I then proceed to tear a 22˝ x 30˝ sheet of BFK into 11˝ x 15˝ quarters upon which I intend to print from 8˝ x 10˝

pinhole negatives or slightly larger digital negatives. (Printmakers are taught to tear their paper rather than cut it so

that the torn edges vaguely resemble the deckle at the ends of each sheet.) This is followed by preshrinking as

described above.

I heard or read somewhere that the l9th century gummists used gelatin/formaldehyde sizing. (Since I am not a

scholarly historian but rather a transmitter of lore, I hope that I can be forgiven for lack of references.) You will read

and hear of many ways to size paper nowadays. With my own prints for many years I sized BFK with two separate

sheer brushed-on coats of gelatin dissolved in hot water and then immersed the dry gelatined paper in a very diluted

formaldehyde bath. The two thin layers of gelatin coat the cotton fibers of the paper without smoothing them or filling

them in, but leave a good ‘tooth’ for the emulsion to grab onto. I’ve discovered that it really is necessary to coat twice

initially to avoid freckles of trapped pigment in highlights.

The formaldehyde bath hardens (polymerizes) the gelatin sizing, making it tougher like hardened plastic. As I was

going through the archives at the Visual Studies Workshop in Rochester, NY, I saw insect egg sacs on unprinted paper

samples sized with unhardened gelatin decades ago. I saw no evidence of insects on unprinted paper samples sized

with gelatin hardened in formaldehyde. However, once a layer of gum bichromate emulsion is printed on paper with

unhardened sizing, the gelatin becomes less available to little critters because wherever the emulsion is printed,

dichromate has hardened the gelatin in another way – with crystalline lattices rather than polymer chains.

Various starches, glues, and acrylic mediums have been recommended for sizing in recent decades. These methods

seem to work better in some hands than in others. Whatever kind of sizing you use, be sure to note it on your paper

since it is not always apparent to the eye or the hand. If you apply sizing on just one side of the paper as I do, note

which side is which. As you grow accustomed to your paper, you will be able to feel the difference between front and

back, sized and un-sized, but fine discernment can be hard to summon when you are in a hurry and you will appreciate

having made notes on the paper itself.

Gelatin Sizing

To make gelatin sizing, sprinkle one level tablespoon (or a Knox packet) of unflavored gelatin as evenly as possible

over the surface of 1 cup (250ml) of cool tap water in a saucepan and let it sit for at least l0 minutes as the gelatin

absorbs water. I have found that any kind of gelatin works, as long as it is unflavored…. (In the past few years I have

been printing on gelatined paper that I don’t harden in formaldehyde with excellent results and the added benefit that

cyanotype can be brushed onto and printed on top of gum layers without beading up.) In a double-boiler or crockpot

that keeps the gelatin solution away from a direct flame, raise the temperature of the gelatin-water to about 130˚F.

(Many times the gelatin has gotten much hotter than 130˚F with no ill effects which makes sense since gelatin for

cooking is nearly brought to a boil.) If you don’t have a thermometer, test the temperature with your fingertip. It is hot

enough when you can’t keep your fingertip immersed. Just before applying the first coat of gelatin, write ‘gel 1’ in the

margin of your paper.

Maintain that temperature range and dip a wide (4˝ or so), soft sponge brush into the hot gelatin and gently apply it to

your taped-down paper so that the surface is evenly coated but not dripping. Leave margins un-sized to avoid gelatin

build-up on the coating surface, and to avoid gluey edges that can stick to clothespins. Look at the paper at a 45

degree angle to make sure the image area is entirely coated. If you are going to hang the paper to dry, make your last

brushstrokes horizontal in regard to the first hanging position. Place the clothespin in the middle of one of the ends of

the sheet so that the tendency of the gelatin to flow downward is counteracted by the direction of the last

brushstrokes. Make sure the wet gelatin surface does not touch or graze anything. When the paper feels dry and you

are ready to apply the second coat of gelatin, write gel 2 in the margin and repeat the coating procedure but this time

apply the gelatin less liberally, using a fresh soft dry brush, if necessary, to pick up excess. The paper will feel

smoother as you apply the second coat. Hang the paper to dry again.

A down side of my approach is that my paper, sized, and then printed upon on one side only, curls inward. I counteract

this tendency by flattening sized paper, once it has dried thoroughly, under heavy plate glass on sheets of foam. Since

I also flatten the same paper between each layer of gum printing, I don’t have a problem with curling and my finished

prints lie flat. Some people immerse their paper in a tray of gelatin and squeegee the excess off of the paper but it is

difficult to maintain the right temperature for the gelatin in a tray and the squeegee operation can become quite a

mess in a classroom situation. The benefit of total submersion is that with gelatin on both sides the paper does not curl

— at least before printing commences (when the gum layers also cause the paper to curl inward). You

could brush gelatin on both sides of the paper to reduce curling which would require 4 separate coating and drying

operations.

Hardening with Formaldehyde

I hesitate to recommend the diluted formaldehyde bath, for fear of its being used in an improperly ventilated area. The

fumes are irritating to the respiratory tract and in prolonged and high concentration can polymerize lung tissue, induce

allergic asthma and do other damage. Pathologists who hunker over tissue preserved in formaldehyde are said to have

the highest incidence of brain cancer of any group. If a fume hood is not available and you cannot work outdoors, skip

the formaldehyde bath and make do with unhardened gelatin. The gelatin may wear off through the abrasion of

brushing emulsion on and manipulating the print during development, and it will dissolve and wash off in non-printed

areas (just where you want it to stay) if subjected to water temperatures over 80˚F, but a fresh layer of gelatin can be

applied before each new coating of emulsion. This is how Lois Johnson worked, using fairly high contrast lith negatives.

Melissa Good makes prints from inkjet separations sizing with 2 layers of unhardened gelatin and doesn’t reapply

gelatin until she has printed 4 or 5 layers of gum emulsion. This approach hasn’t worked so well for me with

continuous-tone pinhole negatives — but seeing Melissa’s latest prints on unhardened gelatin, encouraged me to try

again, this time with digital negatives. My results were pretty good and where there was freckling in highlights I was

driven to make positive digital transparencies and to print from them in titanium white to clean up the highlights. Once

there was gum emulsion printed from a negative and a positive, the paper was sized by the gum itself and no more

freckling occurred.

My former hardening procedure, however, is as follows. Before the formaldehyde step add an ‘f’ to the sizing notes.

Then, under a fume hood (at UArts) or outdoors, wearing gloves and eye protection, tongs in hand, standing so that

you are not downwind, submerge each sheet in a clean tray containing formaldehyde and water mixed 1:40 (l00ml of

37% formaldehyde to 4000ml of water — or 31/2 oz. to a gallon) for 30 seconds to a minute. Outdoors, keep a sheet of

plexi covering the tray, pulling it back just enough to slip the paper in and out. Hold your breath as you drain excess

formaldehyde water from the paper into a corner of the tray, cover the tray, and then hang the paper outside on a line

overnight. At UArts the paper is hung over the tray in the fumehood until it stops dripping and is then hung directly in

front of an exhaust fan to dry overnight. The paper will give off formaldehyde gas for at least 24 hours and should not

be brought into your living space until the sweet smell of formaldehyde is gone. Meanwhile, return the remaining

formaldehyde/water to a sturdy plastic container with a good screw cap and re-use. (I used the same gallon with

occasional replenishment as volume diminishes for over 8 years.) Do not store 37% formaldehyde or the diluted

formaldehyde in your domestic space in case a subtle out-gassing occurs.

Repeated brushing can wear down even hardened gelatin. After 3 or 4 layers of emulsion I routinely resize with one

layer of gelatin that I harden in formaldehyde. After 6 or 7 layers, if the print is not completed, I apply another coat of

gelatin and harden again. Sometimes the slight matte gloss of the hardened gelatin gives a satisfying depth to the

image and there is no need to apply another layer of emulsion.

After reading about combining gelatin and formaldehyde in the same tray, I tried it once and found that there was an

unacceptable exposure to formaldehyde in the hot gelatin and that the gelatin hardened onto the tray and brushes so

that it was almost impossible to remove. I have also read of and tried glyoxal in place of formaldehyde as a hardener of

gelatin. The MSDS health warnings of potential damage to the nervous system from glyoxal are even more dire than

formaldelyde’s and the glyoxal solution must be discarded somehow after each use. When I found that it yellowed my

paper and my image printed blurry, I definitely lost interest.

Unpigmented Gum Bichromate Sizing

A second method of sizing, which I discovered on my own, bypasses the gelatin/formaldehyde method. Apply

ammonium dichromate by itself, as if making a chromatype, and, while it is still wet, generously brush pure

unpigmented gum arabic on the sensitized area and buff it down with soft, dry sponge brushes. I apply the gum after

the dichromate to keep the gum as much on the surface of the paper as possible to promote the sizing effect, but it

can be hard to buff easily without some reduction of viscosity which is provided by the still damp dichromate solution.

When the paper is dry expose it without a light-resist to any kind of actinic light until the yellow chromium salts barely

begin to turn a light beige/tan. This might be 10 seconds in the sun, 40 units in the platemaker, or 1 minute under a

sunlamp.

Gently wash the paper without letting the soft gum coating touch anything except cool water until it drips clear water

when held in your gloved hand above the tray. Hang the sheet to dry, being very careful not to touch the gum coating

which will harden eventually to provide a tough sizing for the paper. This procedure may be performed once for

relatively hard papers with internal sizing but needs to be done twice for a porous soft paper such as BFK Rives. The

light tan color may be removed before printing begins, with a sodium bisulfite bath, or cleared at a later stage in the

gum print — or left on the paper.

Other Sizing

Students have had fairly good results sizing with diluted matte acrylic medium, PVA glue, or gesso. Each of these gluey

materials should be diluted to a milky consistency and applied in at least two layers with drying between applications.

Image formation varies with different sizings. I’ve seen gum printed on gesso sizing by Evan Woldow that under a loupe

revealed a surface like a white dried mud flat with pigment collected in the cracks. A vivid piquant quality emerged

from Evan’s work whereas my gum prints with hardened gelatin sizing are more softly luminous.

Last summer I tried using agar agar (seaweed gelatin available in Asian markets), unhardened as well as hardened in

formaldehyde, as a sizing for BFK Rives but may not have diluted it sufficiently. A little of the powder goes a very long

way. I also tried arrowroot starch but probably needed to cook it more and to harden it as well. More experimentation

remains to be done for those who want a vegetarian alternative to gelatin sizing. You may come up with your own way

of sizing. Experiment with methocellulose.

Or Not to Size

Now that I have described two rather laborious methods for sizing paper that I both teach and use myself, as well as

touching on simpler ways of sizing, I must tell you that I have been shown by Martin Lennon, photographer/printmaker,

that a different approach to the application of gum bichromate emulsion to un-sized paper can result in less staining

and freckling in highlights than I would have thought possible. Coming from a lithographic background, I have buffed

gum bichromate emulsion onto paper with soft dry sponge brushes, rather like buffing gum arabic onto a stone with

clean dry surfaces of cheesecloth. Martin Lennon, instead, uses a Chinese haké brush (white animal hair sewn between

wooden paddles) and slowly, gently lays out ribbons of pigmented emulsion onto un-sized BFK Rives. He demonstrated

his method to a non-silver class with a layer of lamp black emulsion and Dana Leight, graduate student and teaching

assistant at the time, subsequently made gum prints on un-sized BFK, using Martin’s approach, with 3 layers of

pigmented emulsion. Staining and freckling in highlights was not severe enough to reduce contrast significantly and

indeed the faint ghosts of brushstrokes in highlight areas gave character to those passages. I speculate that Martin’s

and Dana’s success on un-sized paper came from the facts that they were using brushes made of animal hair (which I

suspect releases flakes of pigment more easily than sponge), that they did not buff the emulsion into the paper fiber as

I do, and that they were printing from fairly contrasty negatives. Applied Martin’s way in one generous but light stroke,

the emulsion sits on top of the paper while mine gets tangled in the un-sized fibers of the paper with my many feathery

buffing strokes. I encourage students to try Martin’s approach but stand ready to teach sizing strategies when they

seem to be needed.

I’m not able to use his approach with my own work since I desire a smoother surface than can be achieved with one

stroke of emulsion on un-sized BFK and I usually build my prints in several layers of emulsion.

Registration and Taping

The registration of multiple layers of gum emulsion can be accomplished by eye. First, make corners in pencil where

the image should print on the paper. This will help you to cover the image area with emulsion yet maintain uncoated

margins for safe handling. If you decide to register by eye, the initial layer of gum should be a dark one (but still sheer

enough to allow light to penetrate). This dark emulsion should cover the image area and extend just beyond your

marked corners so that it prints the edges of your negative. That way after printing the first layer you can see the four

corners of the negative which will help you register subsequent layers by eye. Beginning with a dark layer also tests

the efficacy of your sizing. It’s better to discover right away if the sizing is adequate than to print two forgiving light

layers and then, when you coat with a dark layer, to have dark freckles of pigment show up in the highlights. Additional

dark layers can be printed later on after resizing.

Attach minimal amounts of clear or frosted tape to opposing sides of whatever you are using as a light-resist. The

hinges of tape on one side of a light-resist, recommended for easy inspection of cyanotype, vandyke, palladium, or

chromatype, don’t work so well for gum bichromate. Although printing-out can show that a gum print is sufficiently

exposed, sometimes a gum print is perfectly exposed with no sign of printing-out because just enough light was

received to harden the emulsion without getting to the tanning stage. This is especially true with digital negatives.

Pieces of tape on one side might not attach the negative properly to paper sensitized with gum emulsion which tends

to curl.

Even though it is transparent or translucent, the tape may print faintly in gum. With a borderless negative, place the

tape so that it overlaps dense parts on edges of the negative; that way, it will scarcely print at all. Use as little tape as

possible, especially on the film. A bit more tape surface may be required to attach the negative to the border of a

curling print but its tack may need to be reduced by touching it to your finger a few times. This will help prevent gum

emulsion from pulling off the borders of the print when exposure is complete and the negative is removed from the

print.

Use the penciled corners (which can be extended like X’s into the margins in case the emulsion hides the actual corner

L’s) as a guide for placing the negative for the first exposure. After exposing, developing, and drying the first dark

layer, coat the printing paper again with a second emulsion layer of any color you desire — light, dark or in-between —

and place it in darkness to dry. When the second layer of emulsion is dry and you are ready to expose it, precise

registration is required. Position clear tape on your negative again. Then take the sensitized print out of the dark drying

area and tape its four corners with drafting tape (or some other tape that will release cleanly) to a light table that is

located in an area with low ambient light.

Turn on the light table and orient the negative on top of the print. Previously printed areas should fill the open areas of

the negative. If you see bright yellow edges around opaque parts of the negative, shift the negative to cover those

areas or else the new color will print in highlight areas as a thin line around the previously printed layer. You can use a

tube of black construction paper placed on top of the light-resist to block out extraneous light for viewing particular

parts of the negative on top of the print. Check the four corners of the image to make sure the negative isn’t off-

register in one direction or another. If the paper has shrunk and the negative cannot be perfectly registered, decide

which segment of the image requires sharp focus and which segment(s), if any, can tolerate a looser registration. After

you position the negative as well as possible, hold the negative in place with one hand and press the bits of tape

attached to the negative onto the print with the other hand.

Registration by means of pin or needle holes through opposing corners of both the negative and the paper also works.

Traditional pin (or button) registration is another option but tends not to work if the holes are on one side of the paper

and even very slight shrinkage has occurred. Tabs can be taped to view camera negatives so that holes don’t have to

be made in the film and I suppose that tabs could be attached to the edges of the print to avoid making holes in the

edges of your prints.

Printed registration marks can be specified in the preparation of digital negatives, both desktop and imagesetter.

These usually work well but their positions should be indicated in pencil on your printing paper so that you brush the

emulsion far enough into the margins of the image for the registration marks to print.

Range of Tones

Let’s assume that you have a negative with as full a range of densities as the 21-step scale and that you are building a

gum image entirely in layers of lamp black, as described earlier in ‘Approaches to Building an Image in Gum’. A

refinement on the idea of giving exposures of varying durations to identical layers of lamp black gum might be to

prepare 3 or 4 different dilutions of lamp black pigment in gum arabic. The first layer could use the gum with the most

pigment combined 1:1 with ammonium dichromate and would get the least exposure so that the 5 steps of separation

would occur in the shadow areas, the clearest parts of the 21-step scale. The next layer might contain less lamp black

pigment in the gum part of the emulsion and is given enough exposure to have its 5 steps of separation fall in the mid-

tone range. Black pigment in a third layer might be even more diluted and could be given much more exposure so that

it did its tonal separating in the upper mid-tones and into the highlights. Sometimes an even more dilute layer with an

extra long exposure is needed to print into very dense highlights. Through these multiple layers of lamp black gum

exposure, and development, a very full tonal range can be extracted from a single black-and-white continuous-tone

negative. This slow building of a print may seem like a limitation of the medium since it is labor intensive, but it is also

a strength. Having to synthesize a full-bodied image, which entails making decisions layer by layer regarding pigment

dilution and exposure time, forces an analysis of image formation and allows for creative decision-making with each

exposure.

A further refinement can be brought to bear by varying the ratios of pigmented gum to dichromate solution from the

normal 1:1. If fewer than 5 steps of separation are desired in a layer of emulsion, increase contrast by using 5 parts of

pigmented gum to only 4 parts of dichromate solution. (Too much pigmented gum will make it hard to spread the thick

emulsion evenly.) If more than 5 steps of separation are desired, decrease contrast by using 4 parts of pigmented gum

to 5 parts of dichromate solution. (Too much dichromate will lower viscosity and highlights may stain or freckle.)

Placing Colors along Tonal Scale

This time, you are exposing through a single black-and-white continuous-tone negative as before, but instead of

placing different dilutions of the same color along the tonal scale you are placing different colors in shadows, mid-

tones, and highlights. Such an approach can produce images in which everything seems to be carved of the same

material bathed in a unifying light with highlights of one color, mid-tones of another, and shadows of yet another. Some

of the formal abstract qualities of black-and-white photography are preserved in this way of handling color.

For instance, brush an initial layer of Antwerp Blue gum emulsion onto your printing paper and expose it under your

negative with just enough light to harden blue tones onto your paper in the most open shadow areas. After

development and drying of that first skeletal layer of blue emulsion, apply a layer of Perylene Maroon emulsion and

expose longer through the negative so that maroon mid-tone values adhere and the blue areas turn brown beneath the

maroon gum plus tanning. After development and drying the maroon layer, apply a layer of Transparent Yellow

emulsion and expose even longer, perhaps much longer, to print into highlights, turning the mid-tones a complex

orange and the blue/maroon shadows even browner. A final barely visible layer of Davy’s Gray, made of iridescent

ground slate, can be given a mega-exposure into the densest highlights which might separate the orb of the noonday

sun from the surrounding sky or a spectral highlight from surrounding chrome (that metal again) on an old-fashioned

car bumper. Since the layers are formed from transparent watercolor locked into gum arabic, shadow detail can remain

visible beneath subsequent layers of more heavily exposed emulsion. If shadow detail is not visible, it may be due to

heavy tan/brown printing-out of the chromium salts. A clearing bath of sodium bisulfite (or sodium metabisulfite or

sodium sulfite) could help to reveal those details along with the true colors of your emulsion — aside from the

gray/green left by the heaviest tanning even after clearing.

Manipulation by Deletion

Students who learn gum printing before being introduced to other non-silver processes are disappointed to find that

the subtractive manipulation they do with gum is impossible with cyanotype, vandyke or palladium. With those

processes, chemical solutions are embedded in paper or in some other organic support, but gum bichromate emulsion

sits on top of sized paper, immediately after development in water, in a soft raised gummy layer that can be brushed

away selectively, at least in highlight and in most mid-tone areas. Selective deletion can give the look of local

coloration even though you may be working from a single black-and-white negative.

As the paper dries, however, the gum emulsion becomes hard and impervious. The lattice structure of the chromium

crystals grips the dried gum so hard that what was raised is now recessed, and the unprinted highlight areas are in

subtle matte relief. New gum layers can be added and manipulated. What is underneath will not be affected. (And as

layers build up, the relief of the white areas increases to such an extent that I can recognize some of my prints from

the backside. This happens even though I flatten my gum prints overnight, after each layer dries, on foam under plate

glass.)

Masking

Another way to achieve an in-color effect is by masking parts of the print-in-progress with pure gum arabic. This idea

came to me from reading about rubber cement-like frisket used in the selective toning of silver prints. Brush a sheer

layer of unpigmented gum arabic onto the area to be masked on your print. After it dries, brush another sheer layer of

pure gum onto the same area and let it dry. Avoid blobby puddles of gum. Then in the normal manner with sponge

brushes, apply and buff gum bichromate emulsion over the entire image including the frisketed area and give as little

exposure as is needed to adhere pigment where desired. If all goes well during development, the gum mask dissolves

and the pigmented emulsion should lift from this area. But you must be warned that if the gum mask is located in a

shadow area that gets a major exposure, dichromate in the emulsion may harden the gum mask and it may not release

as desired.

Another way of controlling the placement of color involves cutting light-resists in the shapes to be masked. Such masks

may be made of rubylith or amberlith film, goldenrod paper, black paper, or anything else that prevents actinic light

from reaching the emulsion. When placed directly on top of your light-resist in contact with sensitized paper (directly

on top of your negative), such a mask will give a hard-edged, cut-out look. If the mask is taped on top of the contact

frame’s glass, with the negative against the sensitized paper underneath the glass, light will spread and soften the

edges of the mask. If you are exposing with a point light source such as the sun, shift the angle of the contact frame

during the exposure to soften harsh shadows. If you are using the platemaker which is another point light source,

common sense would dictate not taping a mask on top of the platemaker’s glass since during exposure anything on the

outside surface of the glass would burn, melt and/or destroy the expensive bulb. Indoor light sources that would work

with the mask on top of the glass include a black light box and a sunlamp.

In addition to placing color where desired, manipulation and masking may be used to bring out some areas and

suppress other areas. Instead of using opaque masks, translucent materials such as frosted mylar can serve as partial

masks to dodge and burn specific areas. Emmet Gowin, the esteemed silver photographer who makes contact prints

from view camera negatives, said, in a lecture at The Photography Place in the early 1980s, that he had never made a

large format negative with the perfect distribution of light and dark. He showed how layers of frosted mylar can be cut

into different shapes and stacked like a contour map to effect a controlled, precise, and repeatable dodging of an

image. Sandwiching his view camera negative against a piece of silver gelatin paper beneath plate glass under the

enlarger lamp, he placed the layers of mylar on top of the 1/4˝ glass. This complex mask allowed varying amounts of

light to pass through it to the negative and photographic paper below. I was inspired by Emmet’s sharing of this

technical information to try the same approach with non-silver processes, especially gum printing, and found that it

worked well. But more often I found myself winging it, dodging parts of an image with pieces of cardboard and my

hands as the gum layer exposed in the sun for one or two minutes.

Finally, there is now the option of a digital mask that can be printed fairly easily from a desktop printer on inkjet or

laser acetate. Complex passages can be selected in Photoshop and feathered edges can be specified in ‘radius’ so that

the mask can be printed in direct contact with the negative on top of the print — or even in direct contact with the print

as the only light-resist for a particular layer of gum emulsion. The ‘gradient’ tool is very handy for large simple

masking.

Color Separations

The methods described above permit a fairly comprehensive palette of color to emerge if watercolors that approximate

the CMYK process colors (cyan, magenta, yellow and black) of commercial offset lithography are used. Antwerp Blue

(Winsor & Newton name) or thalo blue can serve as cyan/process blue (as can a layer of cyanotype brushed either

under or on top of gum layers). W & N Quinacridone Magenta is a true magenta and mixed with Permanent Alizarin

Crimson gives a good process red equivalent for the M layer. Transparent Yellow (a relatively new W & N color that is

warmer and more transparent than cadmium yellow that was used before) works well as process yellow. Lamp Black is

good for process black. Oranges (from magenta and yellow), purples (from magenta and blue), and greens (from blue

and yellow) plus a multitude of browns and grays are created by printing one layer on top of another.

Some gum workers print, using these conventional process color equivalents, from color separation negatives that can

be generated easily in Photoshop after scanning a color image. A small color snapshot can be turned into a large gum

print with great physical presence as printmaker Mira Adornetta was the first to demonstrate at UArts using the Scitex

imagesetter’s maximum format that measures 18˝ by 24˝. Gum prints made this way do not have to be pale like

Beatrix Potter illustrations, although a faded, nostalgic look is easily achieved with a thin layer of each process color.

Gum Bichromate Solvents

While a weak acid sets and hardens a gum print, the solvents to soften and loosen bichromate emulsions are alkalis

such as sodium carbonate powder in water, diluted household ammonia, or diluted household bleach. (Never combine

ammonia and bleach since together they produce tear gas.) There may be times when you wish to brush away a layer

or part of a layer of heavily exposed gum bichromate (a risky but occasionally successful operation) or remove dried

emulsion from a bristle brush or a graduated cylinder. A little bit of sodium carbonate, available in supermarkets as a

washing aid, just a teaspoon to half a gallon, is the odorless way to loosen the tight grip of a bichromated colloid.

Because of this vulnerability to alkalinity, it is recommended that gum prints be stored over long periods of time in

mats that do not contain an alkaline reserve (see ‘Light Impressions’ in “Resources”).

What follows is a step-by-step guide to producing a gum print that also serves as a summary:

MAKING A GUM PRINT

l) Light-Resist: Devise some sort of negative transparency that is the size of your final image. A negative is needed to

produce a positive image because gum emulsion adheres where light penetrates the negative and releases where light

is held back.

2) Printing Paper: Any paper or surface (see Dana Leight’s “Gum Printing on Alternative Surfaces” at end of this

chapter) can be tried, though satisfactory results are not guaranteed. The traditional paper for gum printing is sized

BFK Rives, but satisfactory results have been obtained with Arches Cover, watercolor papers, Pondi paper from India

and other papers too. Prepare paper, if needed, as described earlier.

3) Pigments: Select good tube watercolors, such as Winsor & Newton or Grumbacher (or others carried at Utrecht,

Pearl or Daniel Smith) in hues you want to use in your print. Cheaper student grade watercolors will sometimes work

out nicely but usually there is less pigment per tube and sometimes the colors are not lightfast. Students have made


gum prints of great strength and beauty from inexpensive watercolors, but it is yet to be seen how some of the colors,

other than black and earth tones, will hold up over time.

Finely ground dry pigments can be mixed with gum arabic, adding a drop or two of a surfactant such as Photo-Flo and

a pinch of sugar to facilitate blending. Dyes, in powdered or liquid form, are not recommended. They don’t release

easily, tend to stain, and later fade. They are also rather hazardous in powdered form.

According to William Crawford in his chapter on “Gum Printing” in The Keepers of Light, you should avoid the following

watercolors (even from the best manufacturers) because their “permanence and durability are suspect, especially the

first six: Carmine, Chrome Lemon, Vandyke Brown (the watercolor, not the process), Chrome Yellow, Rose Carthame,

Mauve, Prussian Blue, Crimson Lake, Purple Lake, Gamboge, Hooker’s Green Light, Violet Carmine, Rose Dore. Chrome

colors may be chemically incompatible with certain organic pigments or with the sensitizer.” Also Crawford says to stay

away from Emerald Green (which I read, elsewhere, contains arsenic) and which he says should not be mixed with

other chemicals.

It is interesting to note that in the years since Crawford’s book was published in 1979, many of the colors that he

warned about are no longer manufactured by Winsor & Newton. This includes Chrome Lemon and Chrome Yellow that

were discontinued because of ‘toxicity and lack of permanence’. Winsor Emerald, which took the place of Emerald

Green, does not include arsenic in its list of ingredients but I need to test it for compatibility with gum bichromate. I

have noted in classes that Winsor Green does not adhere well and that Ultramarine Blue doesn’t either and can give off

a sulfurous stench when mixed with at least one kind or condition of gum arabic. Otherwise, believe it or not, there is

still an ample selection of colors, each with a distinct personality and history, from which to choose.

Some Winsor & Newton colors, that I think complement the palette already available with cyanotype and the tanning

effect of dichromate, are: Alizarin Crimson (the new more permanent kind), Quinacridone Magenta, Winsor Red, Bright

Red, Light Red, Perylene Maroon, Winsor Violet, Caput Mortuum Violet, Antwerp Blue, Transparent Yellow, Winsor

Yellow, Indian Yellow, Winsor Orange, Burnt Umber, Sepia, Neutral Tint, Blue Black, Ivory Black, Lamp Black, Payne’s

Gray and Davy’s Gray. Chinese White (which is zinc white) and Titanium White can be used to lighten dark areas or for

printing on dark paper. Titanium White covers better than Chinese White but has a slight yellow cast. Gum artist

Melissa Good, who introduced me to Perylene Maroon when it came out, has also recommended Sap Green, Olive

Green and even another green known as Oxide of Chromium which she found is compatible despite containing

chromium.

You will find that blues, violets, and whites require less exposure time than reds, oranges, yellows and browns. This is

because actinic light finds its way through blues, violets, and whites more easily than through colors that act as masks

to it. I have not quantified the different times required for each color to adhere because there is leeway in the exposure

of gum prints, but I find that I am usually successful increasing or decreasing exposures by 10-20% to compensate for

warm or cool colors.

4) Gum-Pigment: Try to mix the pigmented gum part of your emulsion ahead of time so it can become thoroughly

homogenized, especially if your watercolor is old and dried out. If you are short of time, mix gum with pigment, add the

dichromate solution and pour the complete emulsion through a funnel that has a fine mesh screen. You need the

watery dichromate solution to speed the passage of the pigmented gum through such a screen. Chunks of undissolved

pigment will be held back and prevented from smearing the paper. If your pigment is fresh and the color transparent,

don’t bother about straining.

To make a supply of gum-pigment that can be used for a few prints, squeeze 1/3 the contents of a small tube of

watercolor (such as a W & N 5ml tube) into a little jar with a tight-fitting cap or into a 35mm plastic film canister. Add a

very small amount of gum arabic that equals or is less than the volume of the pigment. Mix the pigment and gum with

a stick of clean smooth matboard or something comparable and keep adding small amounts of gum until the mixture

becomes a slurry. Add more gum and blend until you have about 1/2 of a film can of pigmented gum. Then dip the tip

of a clean, dry 1˝ sponge brush into it and brush the mixture onto a scrap of the sized paper that is identical in kind

and condition to what you’ll be printing on. Or lay down a strip of pigmented gum in one stroke with a haké brush on

un-sized paper if that is how you intend to work. Then place the scrap of sized (or un-sized) paper in cool water for a

few minutes or hold it under a stream of cool running water briefly. It just so happens that if the pigment or its stain

remains on the test scrap, the same pigment or its stain will end up in the highlights of your print when a full emulsion,

including sensitizing dichromate, is brushed on, exposed, and developed. If this amount of color is acceptable in your

highlights and you like the intensity of the brushed out pigment, stop adding gum, but if you want highlights to be

white, or nearly white, keep adding gum and making more tests until the pigment does release completely. Of course

you will save money on pigment the more you dilute it in gum Arabic, as long as results are satisfactory.

If the color you end up with is less saturated than you wanted, it is possible to strengthen the image by recoating the

print (once it has been developed and dried) with the same color and re-exposing it, or by printing over it in a related

color so that the two transparent colors, like glazes, create a third color.

I have many little jars of pigmented gum that I use only occasionally. Poisonous pigments such as the cadmiums keep

well but sometimes mold forms on top of the more benign colors and I have to lift it out with a stick of matboard. Over

time evaporation occurs and I need to add more gum and a few drops of water. A patty of pigment in a watercolor set

is pigment in dried gum that can be used for gum printing by immersing it for as long as it takes to dissolve in liquid

gum and some water. A tube of dried-out watercolor pigment can be salvaged by slitting it open with a utility blade and

soaking the contents in gum and water as long as necessary.

Photography student Emily Rose Chesser made a gum print using a red clay and a gray clay from Cape Cod. We used a

pinch of sugar and a few drops of Photo-Flo to help the clay blend with the gum. Both clays printed beautifully in her

red-clay/gray-clay gum print.

5) Safety & Mixing Dichromate Sensitizer: Before reaching for the bottle of dichromate, put on gloves. Free

disposable latex gloves in medium and large sizes are stored beneath the coating table in the non-silver darkroom at

UArts and should be used when handling dichromates. For dichromate solution we use sturdy plastic dispensing bottles

covered with black tape that will not shatter or spill (much) if dropped or tipped over. Orange crystals tend to form on

the top of the dispenser which will offset onto gloves, contaminating them immediately, so I suggest opening the

dispenser with a piece of paper towel that you dispose of. If, when you pour out your dichromate solution, some of it

drips down the side of the bottle, wipe it off with a damp paper towel.

For those committed gum workers outside of UArts, who are mixing their own dichromate, exercise special caution

when handling the dry crystals by wearing gloves, an apron, protecting your eyes, and perhaps wearing a dust mask.

Nowadays ammonium dichromate is usually sold in a granulated rather than powered form and is not dusty, thus safer

to handle.

I have evolved a simple way of preparing solutions of ammonium dichromate in which I carefully spoon the crystals into

a graduated cylinder up to the l ounce line and add tap water up to 15 ounce mark. (Yes, even Philadelphia tap water

can be used for dichromate solutions.) You will see a variety of dilutions recommended, some of which are much more

concentrated, but I have found my dilution to be as fast as the more concentrated solutions and I certainly believe in

using as little of this toxic heavy metal salt as possible. In fact I mean to try using even more diluted solutions. Last

summer I began using a saturated solution of potassium dichromate, an ounce by volume in close to 30 ounces of

water. Although the exposures took perhaps twice as long I was very pleased with the results. There seemed to be less

yellow staining and tanning.

Dichromate solutions should be stored in darkness in brown or opaque containers but can be handled in subdued room

light. No safelight is needed nor should one be used since it is hard to work safely in orange or red light with orange

liquid. At UArts we use 60 watt tungsten bulbs in clear glass fixtures that hang on the wall about 4 feet above the

coating table. However, once the paper is coated it should be dried in darkness and placed only briefly on a dim light

table for registration. Sensitivity increases as paper dries and is at its height following exposure, so get the exposed

gum print into water ASAP.

After several years, a solution of dichromate will begin to lose its potency. Ideally you will have used it up before it gets

old, but if you are stuck with expired solution, do not pour it down the drain. Save it for a hazardous chemical pick-up

or take it to a designated place where toxic waste is disposed of as well as it can be. Such information should be

obtainable through the phone book or your borough hall or may be online.

6) Necessary Supplies: Before you combine pigmented gum with dichromate, make sure the rest of your supplies

are assembled. You will need:

printing paper, preshrunk & sized if necessary

a pencil for notes & a straightedge if you are designing a test strip

tape — white artist, drafting, or masking tape to attach the printing paper to the coating table; clear or frosted tape

to attach the light-resist to the sensitized paper

clean, dry 3˝ sponge brushes —2 of the new finer #8505 or at least 4 of the older coarser Poly-Brush for each color

(Smaller sponge brushes are OK for covering areas less than 8˝ x 10˝ and you may prefer using bristle brushes.)

disposable gloves for handling the bottle of dichromate, for handling the print as it develops, & for washing sponge

brushes

graduated cylinder that measures milliliters, 45ml (11/2 oz.) or smaller

stirring implements for homogenizing pigmented gum in jars or film canisters & for stirring mixtures of dichromate

solution and pigmented gum in graduated cylinders (We use 6˝ x ≈1/4˝ sticks of scrap rag matboard.)

a shallow container for the complete emulsion that is wide enough for the coating brushes (Plastic bowls or saucers

work well and can be reused.)

tongs or gloves

timer

masking material — rubylith, goldenrod, orange mylar, cardboard — anything opaque & flat with a straight edge to

block out light when making test exposures

tray of cool water for the initial still development

plexiglas or plate glass upon which to manipulate the print

a hose or small watering can for clearing the image with a stream of water

brushes, pieces of sponge, etching blanket, etc. for manipulation of the print

a bigger tray with a Kodak siphon or some other arrangement for final washing

a line with clothespins for drying the washed print

tofu tubs or something like them for soaking and washing sponge brushes before emulsion hardens on them

7) Working Emulsion: Prepare the working emulsion by adding one part gum-pigment mixture to one part

dichromate solution.

Twelve milliliters of working emulsion should make enough emulsion to coat 8˝ x l0˝ areas on 3 sized pieces of paper. I

find that if I am coating 10 or more sheets with 8˝ x 10˝ image areas, it averages out to 3ml emulsion per print but

about 6ml are needed to charge the first brush initially and coat the first print. (To pre-wet the brush in water would

lower the viscosity of the emulsion and could make it harder to clear highlights.)

Although the gum-pigment mixture will keep for months, or even years, in a sealed jar, once dichromate has joined it,

an inexorable hardening process sets in. This happens even in the absence of light, giving the complete emulsion a

working life of usually only a few hours though sometimes longer. To avoid wasting pigment and polluting any more

than necessary, learn to prepare only as much emulsion as you will use during a session.

8 ) Application of Emulsion: Pour the blended complete emulsion from the graduated cylinder into a clean, dry

container that is wide enough for sponge brushes (or a haké brush) to be dipped into. Make sure, if you are using

sponge brushes, that you have a few lined up on the coating table that are dry and soft on the edges. This preparation

is to ensure that there is no delay in grabbing a fresh brush during the critical moments just before the emulsion sets

up and can’t be brushed any more.

Gently, liberally apply all the emulsion you are going to need with the first sponge brush. If that brush ceases to make

progress smoothing the emulsion, grab a fresh brush and continue with quick, light strokes up and down and side to

side, using one surface of the brush on the upstroke and the other surface on the downstroke. The emulsion begins to

set up and will be streaky unless you work fast towards the end. You may sometimes wish for streakiness of emulsion

on a print, but you should be able to brush down the emulsion smoothly when you want to. Consider in what direction

to make your final strokes if they are going to be at all visible. I tend to think symbolically of horizontal strokes as

denoting the passage of time and vertical strokes as gravity.

It is possible to brush complete emulsions of different colors into each other on the same layer but care must be taken

to avoid buildup of emulsion where one color ends and another begins — which can result in emulsion sloughing off

entirely. It helps when making a transition from one color to another on the same layer to dribble and brush out a line

of pure gum arabic with a 1˝ brush between the colors which you then brush the colors into from each side.

Another approach is to coat the paper with straight ammonium dichromate and then apply pigmented gum (see ‘Two

Part Emulsion: Pigmented Gum over Dichromate’ earlier in this chapter). This method produces a more contrasty

image with stronger colors and makes it possible to apply different colors in patches, but it is harder to coat the viscous

pigmented gum evenly without the watery sensitizer present to dilute it. It helps to work the pigmented gum into the

dichromate while the latter is still wet.

9) Drying: If you have buffed down the emulsion so there are no streaks, the print is nearly dry already. Five or ten

minutes of air drying in a dark space with perhaps a few light passes with a hairdryer may be all that is needed to

complete the drying. A gum print does not have to be bone dry the way a vandyke brown print does, but certainly dry

enough so that it does not offset on your negative and stain it irreparably with dichromate as has happened to students

and myself a few times. A wise insurance would be to insert a piece of clear thin acetate between the surface of your

gum print and the emulsion side of a precious irreplaceable negative. Also be sure to inspect the glass and base of

vacuum tables and other contact frames before entrusting print or negative to them. In a shared space it makes sense

to work defensively…

10) Test Strips and Notes: Although it is frustrating to be slowed down at this point, taking the time to make a test

strip will save time in the long run and will teach you much about the nature and possibilities of the medium. One

exposure time cannot be given for every light-resist (negative) for 3 reasons: 1) different film-base-plus-fog densities

and other variables in light-resists; 2) differences in the speeds of different colors (i.e. red slower than blue); and 3)

your idea with a continuous tone negative of where you want to place the 5 steps of separation on a 21-step scale, i.e.

shadows, mid-tones or highlights.

The paper used for the test strip should be identical in kind and condition regarding sizing to that of your final print, but

it need not be as large so long as the critical areas of the negative (both highlight and shadow for each exposure on

the test strip) can be exposed onto it and there are margins extending beyond the negative where ruled lines and

exposure times can be seen without lifting the negative. Design your test strip before applying emulsion to avoid

resting your hand on the sensitized paper or possibly fogging the emulsion through prolonged exposure to light. I like

to use an HB pencil and a straightedge at least 12˝ long to draw lines in the margins.

Find a passage within the negative that includes crucial densities in the parts of the image that matter to you most.

With the test paper on top of the negative on a light table, design the test sheet so that each of the 5 test exposures

contains the range of densities that concern you. Your test sheet may end up divided into cells on a horizontal

landscape, each frame containing a segment of land and sky — the range of densities that concern you. Or the test

strip may be divided into long thin strips in a vertical portrait, each strip recording forehead, eye(s), chin, and neck.

Using the straightedge, draw lines in the opposing margins of the test paper to mark the outer limits of the test strip.

Within those lines draw 4 more sets of lines in the margins so that there are 5 different areas for 5 exposure times. I

avoid drawing lines through the actual image area because the graphite might smear and otherwise obscure slight

differences between one time and another. Mark in pencil on the test strip where any corners or edges of the negative

are located, for coating and registration purposes.

A good test strip goes from being underexposed to being overexposed to reveal the range of possible exposures for

shadow into highlight. Sometimes an exponential progression such as 1, 2, 4, 8, 16 units of exposure runs the gamut of

possibilities better than an additive progression such as 1, 2, 3, 4, 5 units, especially with a continuous-tone negative

that has dense highlights. Whichever progression is used, write the numbers between the lines on both sides of the

area being tested. This will help you place the masking material during the actual exposing of the test strip when the

negative will be hiding your image and all you have to guide you in placing the mask are your lines with times in the

margins.

When you have coated the test sheet with gum emulsion and are ready to make the test exposure, tape the test strip

to the negative and start out giving the shortest exposure to the entire test strip; then cover the part that was to have

that minimum exposure and give the rest of the strip the next increment of exposure, advancing the masking material

to cover the strip that goes with each exposure time, and ending up with one strip at the end that receives the longest

exposure.

You will thank yourself eventually for going to the trouble of making test strips, at least a few times in the beginning, to

get a sense of the range of possibilities with the kind of negative you are using. You will also thank yourself for keeping

notes on the watercolors used, the exposure light source and duration, the date, and any other pertinent information. I

write such notes around the edges of my printing paper and later transfer the information to a notebook if I exhibit, sell

or donate the print. Although it is almost impossible to produce a uniform edition of multi-layered manipulated gum

prints, you can come close with comprehensive notes or can make informed changes.

11) Exposing: Ideally, gum bichromate emulsion should be exposed soon after coating. If coated paper is stored more

than a few hours, especially in hot, humid weather, unexposed parts may not release or severe freckling can occur.

Heat and time as well as actinic light can trigger the hardening of gum emulsion.

Tape or simply lay your negative, emulsion side down for a right-reading image, against the dry sensitized side of the

printing paper (or against a piece of clear acetate that lies on top of the sensitized paper) and place the ensemble in

your contact frame so that light shines through the negative onto your paper. If you are making a test strip under a

275 watt sunlamp at 18˝ with a lith or thin continuous-tone negative or an imagesetter or desktop acetate negative, try

making a test strip with a sequence of 2-minute exposures up to 10 minutes. With the same negative exposing in a

black light box, also try a series of 2-minute exposures. On the platemaker try a series of 20-unit exposures (at least on

our machine with its current calibration). In direct sunlight, try 10-second exposures. It is OK to place the opaque test

strip mask on top of plate glass, rather than directly against the sandwiched negative and print, when exposing in the

sun or under a sunlamp. The light will spread somewhat but with a point light source that casts a strong shadow,

differences between exposure times should be visible. Dense continuous-tone negatives, and other light-resists with a

wide range of densities require much longer exposures to print highlight detail. A test strip, with exposures that double

each time, will be more informative than an additive test strip. Remember that a useful test strip goes from

underexposure to overexposure, covering the range of possibilities.

Sometimes a thin negative that would produce a muddy print in vandyke or palladium will print perfectly in gum, but

the exposure needs to be precise so that the emulsion hardens and releases where desired. A good test strip comes in

handy.

12) Developing: Traditional gum development involves immersion of the print face down in 90°F water for about one

hour. Gum prints developed this way have a matte surface because most of the gum arabic dissolves out of the

emulsion. To have trays tied up an hour for each layer for each gum print, not to mention maintaining 90°

temperatures for those trays, is a logistical nightmare in a class situation. Out of necessity I have evolved shorter

exposures and a shorter coldwater development. This handling turns out to have aesthetic advantages, in my opinion.

More gum arabic is retained on the print, lending a luster as layers build up. The printed areas are in relief as the paper

is drying but when completely dry, the unprinted upon, lighter areas appear raised and the printed areas, gripped by

the dichromated gum, recede, subtly sculpting the paper.

Using our method of development, slip the exposed test strip (or print) face up into a tray of cool water that is at least

2˝ deep. See that the surface of the print is covered with water. Then, wearing gloves (no bare fingers!), lift the print

by diagonally opposing corners, turn it over and lower it slowly into the water again, face down. This way of touching

the water with the center of the print gives air bubbles an escape route from beneath the paper. Air bubbles leave

underdeveloped muddy circles. Avoid having the image area touch the bottom of the tray or anything else because the

emulsion is now soft and easily marred. Let the print or test strip soak for a few minutes with occasional gentle

agitation and a few careful liftings and flippings to speed the release of unexposed areas.

When water in the tray has grown murky from unexposed ammonium dichromate and pigmented gum leaching into it,

lift the print, drain it, and place it carefully in a large washing tray that is elevated enough to accommodate a tray

siphon. The tray should have fairly deep water and, ideally, no other prints floating in it. If other prints are already in

the tray, watch your print to see that it doesn’t get marred — or mar someone else’s print. One gum print in the wash

tray can be face down and another face up on top of it, but not face to face or face to back. It distresses me to see a

delicate gum print being ruined in the final wash through careless handling. However, beginning gum students tend to

overexpose their prints so that rough handling during development doesn’t always pose a problem for them. But they

are producing prints that they had to scrub to clear and which lack the subtlety and sensuous surface that gum is

capable of. In any case, in the final wash tray, adjust the water flow so that the siphon begins to remove dirty water

while adding clean water, but not so hard that the print is buffeted and crimped.

13) Manipulating: After development in water, you can manipulate your gum print if necessary. It is helpful to

practice manipulation on a well-designed test strip. Tilt a clean piece of plexiglas or seamed (smooth-edged) plate

glass against the closer edge of the sink sloping away from you. Lay the soft-surfaced test strip face up on the smooth

support and, holding the print in place with a gloved hand, start gently hosing cool water around its edges with no

pressure. Remember that with a continuous-tone negative the length of your exposure will determine where the 5 or so

steps of tonal separation that a single layer of gum emulsion can render will land on the continuum between clear and

opaque film.

The first segment of the test strip, that is grossly underexposed, will release almost entirely, handled as in the

paragraph above.

The second segment of the test strip, that has had minimal exposure, will render only the clearest most open parts of

the light-resist — in other words the deepest shadows and other dark parts of the image. Those areas should be able to

withstand a gentle flow of cool water. There may be times when you will want a skeletal rendition of a negative. Handle

a print with such a delicately adhered image with special care to avoid marring until washing is complete and the print

is thoroughly dry and tough.

In the third segment of the test strip, highlights will clear in still water and mid-tones will partially release with gentle

cool hosing. This exposure may give the richest rendition of the negative.

With slight overexposure in the fourth segment, highlights may be covered with a veil of pigment that can be removed

with a gentle stream of cool water. Some pressure may be added to the stream if the veil doesn’t lift. If that doesn’t

work, warm the temperature of the stream of water.

The fifth segment that is more grossly over-exposed may require a soak face down in warm water. If that doesn’t

loosen the highlights, try hot water and then sponge brushes. Gentle rubbing with a piece of woolen etching blanket or

something similarly abrasive will sometimes release emulsion.

If you have not made a test strip and you end up grossly over-exposing a layer of emulsion onto well-sized paper, try

sodium carbonate as described on pages 16 and 32.

If your gum print was reasonably well exposed you can work with a stream of water, sponge brushes, and bristle

brushes, selectively removing pigment in the lightly and moderately exposed areas. Fan-shaped brushes help with a

seamless removal of pigment.

When Scott McMahon was a student majoring in Photography at UArts, he deleted gum in scratchy, expressive lines

with the wrong end of his brush to denote rainfall. Later in his gum work he brushed away parts of layers of emulsion

selectively and allowed the brushstrokes to show. Even something as apparently clumsy as a scrap of etching blanket

can be used to delete color in broad lines that look like pastel on rough paper as the paper or the previously printed

color beneath the layer of pigment is revealed. You will probably think of other ways to manipulate gum.

l4) Washing: When you have finished manipulating your print, lift it up by a corner and see if the water that drips off

the bottom corner is clear or tinged with orange dichromate and/or the color of the pigment you exposed. If the water

is not clear, wash the print some more face down in the large tray with the siphon flowing gently until the print drips

clear water. Hang the print from a clothespin to dry and rotate it occasionally. (Don’t stretch it tautly between two

clothespins or it might dry ever so slightly wider on that end than the other.) Clean up carefully. Graduated cylinders

should be rinsed in warm water. If emulsion has begun to dry in the graduate, add some sodium carbonate (or

ammonia or bleach) to dissolve it. Soak sponge brushes briefly in tubs of water (tofu containers work well) and keep

changing the water until it is clear. Shake the brushes in the sink with a snap to your wrist to get rid of water in the

sponges or, if that motion begins to give you carpal tunnel syndrome, press them flat between gloved hands to

squeeze out excess water. Dry them flat, stacked like Lincoln logs on tofu containers with no pressure on the ends of

the sponges. Never dry brushes, either bristle or sponge, resting on their working ends. They will be splayed, crimped

and generally rendered useless.

The dry gum print is tough, safe to handle, and ready to receive new layers without affecting the existing layers. Wash

your hands even if you’ve been wearing gloves.

15) Clearing a Gum Print: You must wait until your print is completely dry, preferably overnight, before clearing it in

sodium bisulfite to get rid of subtle yellow staining of highlights as well as all but the darkest chromatype

underprinting. The mild acidity of this clearing bath allegedly sets (as well as clears) the gum print but I don’t think it is

absolutely necessary to use this bath if you are happy with an uncleared print or if no underprinting is visible. Be sure

to use the sodium bisulfite in a fumehood or outdoors since it has a strong odor that will make you cough. The same is

probably true with sodium metabisulfite though I have not used it. Sodium sulfite does not have an odor but more of it

is required and it takes longer to clear a print. Whatever you clear with, have a tray of water on hand to stop the

action. You may wish to retain some of the warmth of the chromatype underprinting by not clearing it entirely. You can

also apply the clearing agent in different concentrations with a brush to certain areas. Be sure to wash the print for a

few minutes after clearing so that the acidity of the sodium bisulfite does not remain in the paper fibers.

16) Presentation of Print: If you have flattened your print after each layer of printing you can easily mat and frame

it. If your print is very curly, do not ‘break’ it by placing weights on it or putting it in a drymount press. Instead, spray a

fine mist of water on the back of the print to relax the curl and leave the print face up under plate glass on top of foam

or some other porous surface until it has dried.

Occasionally there will be white or light spots on your finished gum print which you will wish to bring down in tone.

Spotone dyes work well on gum prints, sinking right into the emulsion. From among the 6 Spotone colors that are sold

it is possible to find or mix a match with appropriate dilution to spot small areas in gum prints. If these dyes are used to

darken just a tiny light spot it probably will not matter if the dye is not entirely archival and changes a little over time.

If you prefer to spot with watercolor, add a drop of Photo-Flo or some other surfactant to the watercolor to reduce

surface tension and allow the color to sink into the emulsion. The Pitt artist pens by Faber Castell are lightfast. Last

year a range of grays, terras, and landscape colors , all with the brush tips, were introduced. I use Pitt pens to spot my

gum prints. Mistakes can be sponged off with water on a bit of sponge if the print is covered with tough gum emulsion.

If you are matting your gum print, the issue of where to crop it will arise. Do you allow only the image to show,

emphasizing the content of the image and bringing out its pictorial qualities, or do you permit the brushed borders to

show, thus emphasizing the process and revealing the individual colors that formed the image? If showing the borders,

how much should be shown? Should the print be floated on top of a piece of matboard? If you are cropping the image,

do you let the edges of the film show? Can you crop into the image? There are no rules about presentation just as there

are no hard and fast rules about how to work in gum. It is up to you to find your own way of working with this complex

expressive medium.

17) The ‘Failed’ Print: If you are not happy with your completed gum print, do not throw it away. Your teacher, if you

have one, may be able to help you understand what happened and what might help you achieve what you were after.

For instance, if your highlights are freckled with pigment from the last layer of emulsion you applied, the problem is

that your sizing wore away just where you wanted it to work best. This often happens when the sizing is unhardened

gelatin because it is soft and abrades easily; or if you washed your print in water over 80˚, as can happen in the

summer, the gelatin simply dissolved and washed away – this does not happen with hardened gelatin. You probably

didn’t have freckles where previous layers of gum emulsion were already printed because those layers acted as sizing.

Or perhaps over-exposure darkened your highlights. Instead of throwing a print with freckled or muddy highlights into

the trash you might print the highlights from a positive transparency in a layer of titanium white emulsion. If you don’t

already have a full-size positive from making an enlarged negative, a positive can be obtained in the chemical

darkroom by contact printing the negative against another sheet of film or in the digital darkroom by scanning the

negative and generating a positive on inkjet or laser acetate. You may be pleasantly surprised to recover your

highlights and end up with a print that is more interesting than if everything had gone as planned.

Finally, there is no rule (except a self-imposed one) that says you can’t draw, paint or collage on a gum print or work

the gum print into a larger piece. From apparent failure you may be led into a new way of working.

Albumen printingShare

Writer / Chad JarvisPhotographer / Chad Jarvis

Creating and processing albumen paper

Always be careful when handling chemicals. Read the health and safety instructions.

Albumen prints

Presented in this paper are the procedures for making your own albumen prints. This is an involved, fairly time-

consuming process but requires skills well within the abilities of the average person. If you are patient and interested in

the time-honored technique of producing your own hand-coated paper, then you can easily master the art of albumen

printmaking.

Starting point

A well-presented albumen print begins with high quality paper. Lightweight papers (stationery stock or slightly heavier

papers) are better for producing albumen (or other POP) prints than heavier stocks, but the paper must be sufficiently

sized to endure prolonged wetting and should contain no impurities which could stain or otherwise contaminate the

emulsion. Several manufacturers produce 100% rag papers suitable for creating albumen prints, notable examples are

Cranes (Kid Finish 32#, Platinotype or Parchment Wove 44#), Arches (Platinotype) and Strathmore (500 Drawing).

These papers or acceptable substitutes can be purchased from Bostick & Sullivan, Photographer’s Formulary or

most art supply stores. Try to avoid heavier stock, as the paper will absorb the albumen coating, causing prints to lose

sharpness due to the emulsion’s being embedded in the fibers of the paper, rather than resting on it.

Ingredients

Sizing/salting solution

12 eggs or enough for 500ml of egg whites 15-g ammonium chloride or salt 15-ml distilled water

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http://www.alternativephotography.com/wp/processes/health-and-safety

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2-ml 28% acetic (glacial) acid 15-g sodium citrate (optional preservative) 2 drops Kodak PhotoFlo (optional)

Sensitizer

37.5-g silver nitrate 250-ml distilled water 2 drops 6.5-7% potassium dichromate (optional contrast control)

Preparing the albumen

To double coat 50 sheets of 8.5X11 paper, you will need about 500-ml of egg whites. Separate the eggs, avoiding

getting yolk, shells or chalazae (the stringy white stuff) in the whites.

All the ingredients

The high-tech kitchen lab

Pour the 500-ml of egg whites, 2-ml of 28% acetic acid, 15-ml of distilled water and 15-g of ammonium chloride

(sodium chloride or kosher/deiodized table or sea salt may be used as an alternative to ammonium chloride) into a

large glassbowl. Additionally 15-g of sodium citrate may be added as a preservative. This is not necessary if you will

be using your albumen mixture within a couple months and will be using your newly-created paper shortly thereafter.

KitchenAid makes life easy

Scooping off the dirty froth

Beat the mixture with a whisk (an electric hand mixer will make this much less tiring) for a minimum of 30 minutes.

The mixture will become very meringue-like but will not stiffen. The longer the mixture is beaten, the finer the

suspended air bubbles will become until nothing is left but a fine froth.

After beating, cover the bowl with plastic wrap, and place it in a refrigerator overnight. The mixture will settle, leaving

a dirty froth on top. Remove and discard the froth,

Straining the mixture through cheesecloth

The final product

and filter the remaining albumen (approximately 350-ml of a surprisingly free-flowing liquid) through cheesecloth,

folded two or three times, into a clearly labeled glass jar with a plastic lid. Adding a drop or two of a wash aid such

as Kodak PhotoFlo will help prevent the formation of bubbles on the surface of the paper at time of coating. Age the

mixture in a refrigerator for a week or so to further denature it. This is your sizing/salting mixture.

Coating the paper

Pour the albumen into a glass casserole dish. Scrape away any tiny bubbles, which will probably have formed on the

surface of the liquid. Place a sheet of paper, front side down, on the surface of the albumen. (Look for the watermark

while holding the paper up to a light. If the watermark reads correctly, you are looking at the front side of the paper.)

Float the paper on the mixture for three minutes. The edges of the paper, which will curl up and away from the surface

of the liquid, can be pushed down SLIGHTLY to ensure proper contact. According to Farber other methods that can be

used to prevent paper from curling include:

keeping the paper and albumen mixture at the same temperature, lightly dampening the back of the paper or contructing a rectangular-bottomed “boat” out of the the paper.

Care should be used to not get any albumen on the back of the paper, as this will cause an undesirable print-through

effect in the final product. As the paper floats on the mixture, the curled edges will relax to fully coat the surface of the

paper. After three minutes have expired, use a toothpick to lift one corner of the paper, and lift the sheet from the

surface of the albumen, allowing the liquid to drain.

Hang the paper lengthwise, blotting off any excess as the coating dries. A toothpick works well to pop or scrape away

any surface bubbles and to squeegee the thick edge, which will form at the bottom of the paper.

Double coating

Double coating, though not required, produces prints with a glossier finish, more even coating and greater density. This

process increases the level of difficulty of creating albumen prints, though the final product is worthy of the extra

effort. The first albumen coating should be hardened before applying the second using one of the following methods:

fully steam the coated paper, thoroughly warm the paper with an iron or mounting press, protecting the coating with a sheet of dry, clean

mount board, allow the paper to sit in a warm place for several weeks or immerse the paper in an isopropyl alcohol/salt solution.

To double coat the paper using an isopropyl alcohol/salt hardening solution with the albumen formula given, use the

following method. After the single-coated paper has dried, immerse it for 15 seconds in a solution of 70% isopropyl

alcohol with 3% ammonium chloride added. This will harden the albumen for the second coat. When the alcohol has

evaporated (fully – otherwise the second coat won’t stick), float the paper on the surface of the albumen mixture once

again following the previously described procedure. The recommended salt concentration corresponds directly with the

concentration of salt in the albumen coating. (Since 70% isopropyl alcohol will leech salt from the albumen, the same

concentration must exist in both solutions.)

Without this hardening step, the first albumen coating would otherwise wash away with the second coating. Hang to

dry from the opposite side for even results, blotting away any excess along the bottom edge. The paper will probably

curl severely; it may be straightened in a warm mounting press.

Sensitizing the paper

Coated paper will keep for several weeks if sensitizing is to be performed at a later time; however, it is best to sensitize

the paper as soon as it is dry. Wear rubber gloves unless you want brown/black/purple stains on your fingers,

fingernails and/or clothing. Silver nitrate will react with the salt of your skin to form silver chloride, just as it does on

paper, and will “develop out” in a matter of a minute or two in sunlight. Wearing safety glasses is also recommended,

for silver nitrate can cause permanent damage if even a small amount is splashed into the eyes. All of the following

techniques may be carried out in subdued (incandescent) room lighting. Avoid fluorescent lamps and other sources of

UV light.

In an amber glass bottle with a plastic top mix 37.5-g of silver nitrate with 250-ml of distilled water to make a 15%

solution. Initially the solution will be cloudy due to the reaction between the silver nitrate and the salts and minerals in

the water. The precipitate will settle overnight and is of no consequence. Store the sesitizer in a cool, dark place.

Method 1 – Floatation coating

Pour 15% silver nitrate solution into a flat-bottomed tray. The glass casserole dish used for albumen coating will work

butMUST be cleaned thoroughly after use if food is to be ingested from it. WARNING: Ingestion of any heavy

metal can be toxic; it is best to dedicate lab ware to these procedures. Float the coated paper on the surface

of the solution for three minutes, avoiding air bubbles. Peel the paper from the surface, and hang to dry.

Some salt will inevitably leech from the paper surface, reacting with the silver nitrate solution and forming a precipitate

which will eventually settle on the bottom of the coating tray and storage bottle. This is the major drawback to this

method – waste. As more and more chloride ions saturate the silver nitrate solution, it will become darker in color and

less effective. Some of this potential loss of silver nitrate can be combated by allowing the solution to sit for an hour or

two after completing sensitization, perhaps while making a print or two, to settle the precipitate. While slowly and

carefully pouring the liquid back into its storage bottle, forego the last few milliliters, preventing the heavier precipitate

from being mixed with the solution. Filtering off the precipitate after every use will go a long way toward extending the

life of the silver nitrate solution.

Method 2 – Glass rod/brush coating

Tape the albumen-coated paper to a sheet of plate glass with drafting tape. If the negative to be printed is smaller than

the paper lay the negative on the paper and lightly mark off the corners with a pencil. Use these marks as a guide for

coating.

Transfer 45 drops (for an 8×10; use a proportional amount for other sizes of paper) of 15% silver nitrate solution in a

plastic medicine cup. The small condiment cups used by fast food restaurants are perfect. Optionally add 9 drops (for

8×10; use a proportional amount for other sizes of paper) of gum arabic solution, which will aid in spreading the

emulsion. Mix the solutions by swirling them in the cup. Use a brush without a metal ferrule, which silver nitrate will

rapidly react with, or a glass coating rod to apply the solution to the paper. A coating rod, also available from Bostick

& Sullivanor Photographer’s Formulary, is the preferred device for spreading the emulsion, since creating streak-

free papers is rather difficult, though not impossible, with a brush. The addition of gum arabic will give the solution an

oily appearance, making seeing and spreading the coating easier.

http://www.photoformulary.com/



To brush coat tip the glass, to which the paper has been taped, at a 45 degree angle and paint the silver nitrate

coating from top to bottom, drawing the brush from one side to the other, overlapping each stripe by about half the

width of the stroke. Recoat the brush after each stroke.

To coat with a glass rod lay the plate glass, to which the paper has been taped, flat. Pour a “bead” of silver nitrate

solution on the paper along the edge of the glass rod. Lifting the rod just slightly from the surface of the paper and

wiggling it slightly will cause a capillary action to draw the solution along the length of the rod. Lower the glass rod to

the surface of the paper, and swipe it across the paper. At the end of the paper lift the rod slightly from the surface of

the paper, and swipe it across the paper in the opposite direction. Performing this operation several times will ensure a

smooth, even coating. If the sensitizer is absorbed by the paper too rapidly, the paper is not sized well enough to coat

using a rod. Either try another brand/type of paper, pre-size the paper, apply another coat of albumen, or use the

floatation method of sensitizing the paper.

The paper may be air-dried or blown dry while taped to the glass or may be carefully removed from the glass and hung

to dry.

Method 2 – Wash coating

Tape the albumen-coated paper to a sheet of plate glass with drafting tape. If the negative to be printed is smaller than

the paper lay the negative on the paper and lightly mark off the corners with a pencil. Use these marks as a guide for

coating. Tilt the glass plate about 45 degrees for coating.

Add 3 or 4 milliliters of 15% silver nitrate to a small test tube, and stuff a wad of cotton snugly into it so that a third of

the wad protrudes from the end. Tilt the test tube to allow the solution to fully saturate the cotton.

Hold the test tube at a right angle to the paper, and starting from the top left corner, lightly “paint” a streak of solution

across the top of the paper. When the right edge of the paper is reached, paint a streak in the opposite direction,

making sure that the streaks of solution overlap slightly, spreading the bead of solution, which gathers at the bottom of

each stroke. Continue this pattern, right-left, left-right, right-left, until the end of the paper is reached. The paper will

have a uniform coating and will show no evidence of streaking when done correctly. Air or hang dry. Remove the

cotton with tweezers and discard.

Negative Requirements

Albumen paper requires several items somewhat unique to alternative processes. The first requirement is a negative

with a density range of 1.8 to 2.0, as the extreme tonal range of albumen paper will cause a “normal” negative to print

very flat. The second is a contact printing frame with a split back, which enables monitoring of the printing-out process.

Third, some sort of toner is needed, usually gold or selenium, unless a brown-orange print color is desired. The fourth

requirement is a bright, sunny day, since albumen is very sensitive to ultraviolet light, and the best source of this

radiation is the sun. The last (absolute) necessity is patience…and lots of it.

Exposing

Loading – This step must be performed in subdued light. Load a contact printing frame with paper and a negative in

typical fashion. (Place the back, spring side down, on a flat surface. Place the paper to be exposed on top of the back,

emulsion side up. Place a negative on the paper, emulsion side down. Cover with the (CLEAN) glass from the print

frame. Place the frame on top of the entire assembly. Flip the frame over, so that the spring side is facing up, and

clamp shut.) Once the assembly has been examined for straightness, cleanliness, etc., place the print frame in the sun

for printing.

Printing – The amount of time required to fully print out a silver chloride print will vary depending on the strength of

the light source (by the way, UV printers may be used in lieu of the sun) and the density of the negative. Some prints

will take as little as a minute or two, while others may take 15 to 20 minutes to produce. The summer sun, since it is

much higher in the sky than it is in the winter, will dramatically shorten print times. Prints may also be produced by

placing the print frame toward open sky, which yields higher contrast images but takes considerably longer due to the

lack of direct sunlight.

After some time has passed, remove the frame from the light source, and open half of the split back of the print frame.

Incredible! This is why it’s called printing-out paper! The image already exists on the paper, but this is where the

process gets tricky. Toning and fixing will bleach the print somewhat, while drying will darken it. A little trial and error

is required to determine when to stop printing. The general rule of thumb is to print until the highlights start to show

detail. The shadow areas will appear quite dark most likely but will bleach more than enough to show detail. The toning

procedure being used should also be considered at this time. Toning in gold before fixing is rather straightforward, and

follows the aforementioned rule of thumb. Toning in gold after fixing will require exposing the print to light until it is

considerably darker than one would think is “normal”. This is because fixing the print first will bleach it much more

than toning first. At this point it should be mentioned that when using selenium toner, the print should be fixed BEFORE

it is toned, otherwise the toner will react with the silver chloride in the print and will make the print “fuzzy” in

appearance.

Processing

Rinsing – Once the print has been exposed to an acceptable level, remove it from the print frame and rinse it in

running water. The water will be murky at first as unreacted silver salt is rinsed away. As it is rinsed the print will turn

from a bluish-purple color to an orange-brown color as the reaction is stopped. This will probably take about 30

seconds but should be continued until the water is clear, as excess silver will quickly exhaust the toning solution. If a

small print is being made on larger paper (and the dark edge will ultimately be trimmed away), trim any excessive dark

border from the print. There is no point to using (and wasting) precious gold toner on paper, which is going to be

discarded anyway.

Toning – After rinsing, slip the print into the toning solution, and watch for a color change while agitating. Usually

toning times run anywhere from three to twelve minutes, with the longer times producing the coldest tones. The thing

to keep in mind here is that the color of the print while it is in the toner has little to do with the ultimate color of the

print. Watch for the amount of color CHANGE to determine when to stop toning. (Yes… more trial and error.) After a

few attempts instinct will guide the process.

Fixing – Prints should be fixed in two baths of non-hardening fixer for approximately 5 minutes each. As they are being

fixed, the prints will experience yet another color shift, which will closely resemble the look of the final print. Bear in

mind that a considerable dry-down effect will impact the final look of the print. If a print looks great while sitting in the

fixer, it is guaranteed to be too dark once dried.

Washing – Before washing, soak in a hypo clear (use Kodak HCA or one tablespoon EDTA plus one tablespoon sodium

sulfite to a gallon of water) bath for two to three minutes. Wash prints for 60 to 90 minutes (only about 30 minutes is

required if using hypo clear) in running water, preferably in an archival print washer. One of the undeniably great

virtues of albumen paper is that a properly washed print will outlive the artist who produced it (as well as his children

and his grandchildren). Silver chloride prints exist today which were produced over 150 years ago and have withstood

the rigors of time with amazing permanence. Hang prints to dry, and straighten in a dry mounting press.

Alternative toning methods – If selenium or gold toning AFTER fixing is desired, rinse and fix the print as described

above, then fully wash. Once the print has been washed thoroughly, tone in either gold or selenium. Then wash again

for another 30 minutes. This method of toning is not necessary for gold, but is absolutely required if toning in selenium.

Keep in mind that prints produced using this method will be vastly different from those created using the standard

method of toning. (The difference is in the point at which bleaching occurs.)

Consider toning with tea or coffee as well. Steep five or six tea bags (no need to use any elaborate blend; the standard

orange pekoe will do fine) in a quart of water. Let cool, and tone away. Surprisingly teas and coffee are archivally

permanent but may require extended washing.

Toning

The only chemical that is absolutely required for processing albumen paper is plain non-hardening (sodium thiosulfate)

fixer. Kodak RapidFix (without the hardener – part b) is a suitable product. Remember: only use part A of the product;

the hardener will ruin an albumen print by severely over-bleaching it. Dilute the stock solution with water to create a

1:7 working solution. Two fixing baths are recommended, using the typical rotation method to avoid exhaustion of the

fixer.

If a print tone other than ugly orange is desired, a toner should be used. Here are several popular toning formulae:

Two-part gold thiocyanateStock Solution

Part A Part B

Distilled water 490ml Distilled water 500ml

Gold chloride 1% solution 10ml Sodium thiocyanate 10g

Working Solution

Distilled water 900ml

Part A 50ml

Part B 50ml

These stock solutions have an indefinite shelf life.

Upon mixing parts A and B the solution will turn a bright red color, which will quickly dissipate to yield a clear liquid.

This is the working strength solution to be used for this session only, as gold thiocyanate is quickly rendered useless by

oxidation. After toning each 8×10 print, add 8ml of each stock solution to maintain consistency. Tone print before

fixing.

Stock/Working Solution


Gold chloride 1% solution 6ml

Borax 3g

Distilled water to make 400ml

Gold borax

This toner keeps well, may be reused and can be replenished. Experiment with different strengths of toner to expand

or contract toning times. Tone print before fixing.

Stock/Working Solution


Kodak Rapid Selenium Toner 1-2ml

Selenium

Experimentation will be required to hone selenium toning, which can be finnicky. One is better off toning too slowly

than too fast, so a low concentration is the prescription for best control. Fast toning in selenium can produce

interesting split-toning effects. Tone print after fixing.

Image below: Devil’s Backbone – by Chad Jarvis, gold toned albumen print.

Pour toner and fixer into trays one size larger than the paper being used (11×14 tray for 8×10 prints). Ribbed trays

may be used; however, the prints must be constantly agitated to avoid having bright lines form where the paper

contacts the tray. Flat trays do not have this problem and are better for fully submerging the print, since, to avoid

waste, small amounts of toner are used.

Notes

Albumen papers should be used within hours of sensitization, otherwise a 1.5 to 2 stop reduction in density and speed can be expected. This can purportedly be countered somewhat by adding 15-g of sodium citrate to the albumen solution during its initial preparation.

Print contrast can be boosted through the addition of a drop or two of 6.5-7% (2-g/30-ml) potassium dichromate to the sensitizing solution. WARNING: Dichromates are highly toxic and should be handled with great care to avoid accidental inhalation or ingestion.

Albumen coating solution may be aged for up to several months to further denature the solution. This denaturing process actually “unwinds” the molecules which form the albumen protein, making the solution less viscous. Some have noted, “the older the better”.

Albumen prints require negatives of exceedingly high contrast range, usually above 2.0, dictating the need for full exposure (at least one stop more than a negative to be used for a silver gelatin print) and N+2 development. These negatives will comonly exceed the contrast range of silver gelatin papers. Negatives that are difficult to print on grade 0 or 1 paper can often be “rescued” with albumen, salted or other printing-out papers.

The fundamentals of temperaprintWriter / by Alex Chater and Peter Fredrick

Peter Fredrick and Alex Chater explains the colorful temperaprint process.

Always be careful when handling chemicals. Read the health and safety instructions.

http://www.alternativephotography.com/wp/processes/health-and-safety

In the beginning there was the egg.

Eggs have been used as a binding medium for pigment paint since primitive times. This is all about using eggs to

make light sensitive emulsions containing pigment. Worked photographically, these have the surface quality of a

classic Egg-Tempera painting, giving the process its name.

Image above: Beside the Sea by Peter Fredrick

The process is applied to a suitable substrate in a very similar manner to Egg-Tempera painting. The image is built

up layer by layer. Often several layers going to make a single coat, and a number of coats to make a final

Temperaprint.

Process outline

Before you start Make sure you have a safe, clean environment.

Have all the tools and materials you need at hand Prepare the egg 3 Make a saturated solution of ammonium dichromate, SAT/SOL Make a Standard Emulsion Mix, (STEM) Add colour to the STEM Coat the Yupo/substrate with Coloured Temperaprint Emulsion Dry the coated Yupo/substrate Register the Yupo/substrate to the negative to be printed Load the registered Yupo/substrate plus negative into contact

Frame Expose to a light source rich in Ultra-Violet radiation Develop Clear Final wash Dry

Introduction

We will cover the fundamentals of the process and find out how we can safely and effectively set up and make

Temperaprints. By following the guidance in this fundamentals section, step by step, you will produce a

good Temperaprint. It will be precise and practical. However we will not go into any more detail than is necessary,

preferring instead to inform you of the basic major considerations, which underlie the working practices of the process.

Image above: Beside the pool by Peter Fredrick

We will cover the manufacture of the Temperaprint emulsion, how to coat that emulsion, the exposure, wash off and

final clearing of the residual dichromate stains ready to lay on further coats. Where possible specialist techniques will

be covered in their relevant chapters and can be considered once you have achieved an understanding of these basic

fundamentals.

Temperaprint Emulsion

The Temperaprint emulsion is a light sensitive compound and as such needs to be worked in a safe light situation,

such as any other photographic emulsion, but it is nowhere near as sensitive as regular photographic

materials, so the normal darkroom requirement does not apply. Sun and daylight must be completely

excluded. You should work by the light of an ordinary filament light bulb not stronger than 100 watt at a reasonable

distance and not fluorescent tubes. You will need to see what you are doing so don’t handicap yourself by being to

mean with the light, but don’t be unaware of it either. The mixture is light sensitive. The emulsion itself consists of

three major parts, whole egg, sensitizer and colouring matter. The following descriptions will take you through

the sequential construction of this emulsion.

1Preparing the Egg: Tools Materials

Three large eggs Sealable container Tea strainer preferably stainless steel 500ml Measuring vessel

Break three eggs into a sealable container that is large enough to allow plenty of room for the egg to splosh about.

Once sealed shake the container vigorously to mix up the egg into a uniform liquid state. Always use the freshest

egg possible. Store bought eggs work fine providing they are fresh. A fresh egg will have a strong sac and will form a

firm mound. Over time, the sac weakens, as does the binding strength of its contents. The type of egg used can also

affect binding strength. Fresh eggs from free-range chickens will produce a stronger binder because of the rich, viscous

yolks.

Though appearing uniform the egg will have small clots, the yoke sack, speck etc. and possibly pieces of eggshell that

have fallen in. So it will be necessary to remove these. Filter the egg through a fine tea strainer into the

measuring vessel, remove the strainer as soon as the flow has dropped off and wash. What you will see are the white

stingy clots and yoke sack washing away down the sink. If this raw egg is not correctly filtered these stringy semi-

clotted parts of the egg will pass into the emulsion stage where they will get up to all kinds of mischief, on to the roller

and coating area and form irregular lighter patches or blotchiness to appear in the print. It is sound practice, to make

sure that you wash and put up to drain and dry all the tools [such as in this case the sealable container, measuring

vessel, tea-strainer] at the end of each stage.

2To make a Saturated Solution Tools materials

Safelighting 100watt filament (household bulb) Clean sink with running water Glass container with a sealable lid. Distilled water Protective Gloves Ammonium Dichromate powdered chemical Dark brown glass storage container 5ml spoon preferably stainless steel.

A saturated solution is where, water reaches a point at which it is unable absorb any more of a

dissolvable chemical, and becomes saturated. Once this condition is reached any further additions of the chemical

will not be absorbed and it will just sit on the bottom of its container until further water is added. A saturated

solution will always be the same, and is therefore known and constant.

You can use bottled, de-ionised, or still spa water for the purpose. The best water to use is distilled water. Never

use tap water! To this water is added Ammonium Dichromate, which is the actual sensitizer. It is these chemicals when

mixed with a colloid such as egg. That has the effect of hardening the colloid in direct proportion to the amount of light

that it receives. Rendering it insoluble or tanning as it is sometimes described. Making a saturated solution is a very

easy task. Work cleanly and keep the chemistry contained to an area that can be cleaned, and has running water such

as a sink, and wear protective/disposable gloves.

Take a glass container with a sealable lid and add 100ml of pure water. To this add two heaped spoons of

Ammonium Dichromate crystals and close the container. You will notice that the water turns yellow and that the

crystals are sitting on the bottom, now agitate the container for thirty seconds. To check your progress let the

crystals settle. The fine dust like particles will have dissolved away first, so what you should see when it clears is just

the larger lump’s looking rather like sugar crystals in water. Once most of the crystals have dissolved, add another

heaped spoon and continue to agitate, checking periodically on your progress. When you notice that the fine particles

remain, as slurry on the bottom, and no amount of agitation will get them to dissolve, the solution is now saturated.

Keeping the glass container sealed, wash under running water to remove any sensitizer that may have

escaped or is trapped in the threads of the lid and clean up the area. In this saturated state the solution will last for

months provided it is kept from the light in a dark brown glass container To maintain the saturated solution, add more

of the distilled water or Ammonium Dichromate, always ensuring that a fine slurry of crystals is present on the bottom.

Again make sure that all the containers and tools you have used are washed up and put to dry.

Issues and Concerns

All chemistry can be considered potentially dangerous and therefore should be treated with respect.

1. You should not inhale the dust.

2. Use protective or disposable gloves when mixing the sensitizer.3. Remove any splashes on your skin immediately.

STEM

STEM stands for Standard Emulsion Mix, (STEM). It is a mixture primarily of the whole egg with Ammonium Dichromate,

which is our sensitizer. Each part needs to be prepared separately and then brought together in the right proportions. It

is at this stage of the process that the STEM can be adjusted for particular working characteristic. Though not

complicated in any way, it should be born in mind that it is important that the measuring is done accurately for results

to be consistent.

3Assembling the STEM Tools materials

Sealable container 500ml Measuring vessel

To complete the STEM, measure out a 100ml of the filtered liquid egg into a sealable container. Now add 50ml of

saturated sensitizer solution. Seal the container and agitate vigorously for ten to twenty seconds to ensure that the two

liquids are fully mixed. When you open the jar you will see a frothed up orange liquid. Do not worry about this, the froth

soon settles down. This is the basic STEM mix and is transferred into a measuring jug.

It is at this stage that various adjustments can be made to the basic STEM. Other constituent’s such as

plasticizer’s flow enhancer’s, other elements, and colloids can be added to improve performance.

Only make up enough standard emulsion for one printmaking session of say three hours duration. Given

time this emulsion will spoil due to dark reaction effects that are similar to the way that milk goes sour with time and

temperature. Therefore the STEM must be discarded at the end of each print session even you have made up a large

quantity. IT CANNOT be stored for later use.


4Colouring the STEM Solution

The colouring of the STEM can be done in a number of ways using a variety of colouring materials. In this initial

method, we will use a painting medium to colour the STEM solution, {which we now call the Temperaprint

Emulsion.} artist quality acrylic paint is employed. There are many different brands and all will work; though some may

not be as strong in pigmentation as others may. We use an acrylic paint known as Liquitex in little bottles and

jars. A highly concentrated colourant which is added in a fixed proportion by volume to the Temperaprint

Emulsion. You may also use raw powdered pigments, or watercolours in which case you may wish to add acrylic when

assembling the Temperaprint Emulsion. Omission of this element is not a catastrophe. It only means that the resultant

image that you get after you have exposed and washed off will be a little softer both in edge and in its physical

properties. Dyes are not normally suitable for use, despite the fact that they are water based and will work. Almost all

dyes are fugitive and therefore of no real value in a system that has great archival potential, such as Temperaprint.

Tools Materials

1/2 inch Brush STEM solution Bottle/jar of Acrylic Paint [Liquitex] 5ml Measuring Spoon preferably stainless steel /or a syringe without needle Small Pallet Knife

Take the 5ml spoon and squeeze out or pour enough paint to make a level spoon full of paint, if necessary

use the pallet knife to ensure accuracy. A very accurate alternative method is to use a 5ml plastic syringe. Now use

the brush to move the paint into a suitable container or the paint tray. Add 5 ml of the STEM solution and

begin to work the paint and STEM solution into each other until they are thoroughly uniform and mixed.

Now add a further 5-ml and again work them together. The important issue is to ensure as even dispersion as

possible, and not to end up with clumps of pure paint sitting in the bottom of the container or paint tray. Initially this

means working the paint from it original stiff consistency to a liquid through a series of additions. As this progresses it

will get easier to mix together as the mix becomes more and more fluid.

There can be few hard and fast rules to the correct amount of colorant to STEM solution as the variables

in the supply are just too vast. Experience and getting to know your materials is in practice the only sure way of

knowing absolutely. It is important to remember that there are two ways to change colour saturation or tonal density.

One is to increase or decrease the amount of pigment in the mix. Or secondly to print a number identical coats one on

top of the other in a multiple layer approach. In practice you will tend to use a mixture of both these methods. However

it is noticeable that once the ratio drops below five parts STEM solution to one part paint the working characteristics

start to radically change. Coats will become heavy, exposure time will be significantly increased and the contrast will

become excessive until eventually you are unable to gain a good even coat or exposure.

The following provides a general guide to the limitations of how much colourant it is possible to load into a coat: -

Use one level spoonful of acrylic paint as a standard unit of measure i.e. 5 ml: -

Chromatically Spoons of Emulsion

Strong Four

Medium [normal] Six

Thin Eight

Glaze Twelve

It is very important to measure these quantities carefully, and consistently. What has to understand, is that

this coloured Temperaprint emulsion. Is not just some messy paint, but in fact a precise photo-sensitive emulsion.


Coating Introduction

No coating system is without its problems; in fact the main reason that the photographic manufacturers gained

dominance historically is that they could successfully coat photographic materials to a high level of perfection, by the

application of precise mechanical factory technique.

The principle custom hand coating methods can be summarised as follows: -

Airbrush Brushing hair/foam Buffing Dip or float on methods Foam roller systems Glass rod K/Graber bar

At the moment our favoured coating tool is the foam roller. Many years have been spent refining the technique to

get the exact balance in the egg emulsion to print onto a sheet of Yupo/substrate. The foam roller has one defect when

used on a smooth non-absorbent substrate such as Yupo [laminated polypropylene] it gives a pronounced texture.

These footprints of the foam will normally need two or three coatings to disappear and give a smooth full-bodied

colour. What has to be born in mind that this process works best in a multiple layer manner! Several layers

often go the make a single coat and a number of coatings go to make the final image. So the foam footprint will tend to

disappear quite rapidly of its own accord as printmaking progresses.

6The substrate.

Choice

The relationship between the emulsion or paint and the surface quality of the substrate onto which it will be laid is

extremely complex. They both need to be matched very carefully. Rather like a hand snugly fitting into a glove.

For instance ideally we would like in the School Temperaprint to employ watercolour paper, with its beautiful textural

surface. However this material has a number of defects that do not favour its use with our process. It needs to be very

heavily sized to work efficiently. This heavy sizing destroys the very surface texture that is its main

attraction.

The problem lies with the absorbent nature of the material. This is a required characteristic for watercolour paper as

easy staining is part and parcel of the watercolour painting technique.

However the unexposed soluble egg emulsion has to be removed in our process which is part and parcel of the

processing cycle. The egg emulsion is far to adhesive to be used in this manner on unsized watercolour paper. The

soluble non-image would just not come out of the paper fibre, resulting in massive pigment stain. Secondly the

watercolour paper is inherently unstable from a dimensional point of view. It stretches and shrinks during the

processing cycle. Even when dry it will still change it shape in response to relative humidity and temperature change a

characteristic that makes fine registration difficult to achieve. As the process is by its very nature a multiple coat

method of printmaking. The final image is constructed of a number of tonal and/or colour coatings, each in exact

register; it is difficult, if not impossible, to achieve this aim, with normal untreated watercolour paper.

7Ideal Base

We have found that an impervious base seems to work best. It facilitates a stain free surface, and allows for an

accurate system of registration. Thus in one stroke solving the problems, inherent in other processes. We mainly use a

polypropylene plastic paper known as Synteape in the UK and in the States the product is called Kimdura.

However it is manufactured by the Oji-Yuka Synthetic Paper of Japan and is called Yupo and can be sourced at their

website.

Alternative substrates

This does not mean that there are no alternatives to this excellent product. Semi-matt RC photopaper can also be

employed if the sliver gelatine emulsion is physically removed with strong domestic bleach. Standard watercolour

paper works if it is strongly sized. We have found that a 10% to 12% solution of gelatine to be effective. Or two neat

coats of Liquatex matte medium. This changes the quality of the watercolour paper surface to a pleasant sheen. Other

substrates such as wood, stone, metal, fabric and ceramics will be dealt with in the advanced section of the book. The

virtue of this process is the ease with which it will happily coat onto a great variety of substrate surfaces.

8The Environment Tools Materials

Safelighting 100 watt filament (household bulb) Clean working area Glass sheets twice the size of the piece of paper. Piece of Synteape/Kimdura/Yupo larger than the print size Masking Tape Paint tray 8-x 4 inch Foam Roller 4inch Coloured Temperaprint Emulsion Paint brush 1/2inch Kitchen Paper towel Hairdryer

http://www.yupo.com/welcome.html

http://www.yupo.com/welcome.html

The Temperaprint emulsion is a light sensitive compound and as such needs to be worked in a safe

light situation, such as any other photographic emulsion, but it is nowhere near as sensitive as regular photographic

materials, so the normal darkroom requirement does not apply. Sun and daylight must be completely excluded.

You should work by the light of an ordinary filament light bulb not stronger than 100 watt at a reasonable distance and

keep any fluorescent tubes turned off. You will need to see what you are doing so don’t handicap yourself by being too

mean with the light, but don’t be unaware of it either. The mixture is light sensitive. The working environment must be

clean and as free of clutter and dust free as is practically possible. It is essential that the work surfaces are kept

squeaky clean from commencement to conclusion of the printmaking. The Temperaprint emulsion will readily pick up

any dust, hair, or other debris in its close proximity.

9Coating the Emulsion

Take a sheet of glass; place onto a clean work surface. Attach a piece of Yupo/substrate to this glass, with

masking tape applied to the diagonal corners. Ideally the sheet of glass should be at least twice the size of the piece of

paper. You should ensure that your paper has a sufficient border around the actual print area to allow plenty of room

for you to stay on the paper during the roll coating. This is good practice as it means that you are keeping the coating

environment clean because all unwanted emulsion will be on the paper surface, not on the glass, and therefore will

conveniently wash away during the print development stage. Take a four-inch acrylic foam paint roller, and a

small paint tray, the sort that you can buy for using with gloss paint. This tray holds a convenient amount of the

emulsion, as a minimum say 25ml which will be enough to lay up to 5 coats, and also provides a ribbed palette which

can be employed to contain and control the foam roller. Pour a working amount of Temperaprint emulsion into

this tray. Stir the emulsion with a small brush to ensure that it is completely smooth and homogenous. Place the

roller in the tray, charge up until the roller has absorbed a “generous” amount of the mix, then roll out vigorously

onto the ribbed palette followed byclean newsprint until it reaches a conditioned state, neither too wet nor too dry

just damp.

A convenient way to control the amount of the mixture in the roller for subsequent coating is to paint the mixture on to

the ribbed part of the paint tray and then reload the roller from there. The mixture will get caught on the ribs of the

tray and the amount that is loaded on to the roller can be quite accurately controlled by this method. This way you get

to know to how much of the mixture you need to replenish the roller to keep it in the ideal coating condition. When you

begin to coat using the roller, roll in one direction only, not backwards and forwards. Roll from east to west, then when

you reach the west, lift up the roller and start from the east again. Repeat over and over again; roll north to south, east

to west, change direction from time to time. This action will seem a bit strange at first but you will soon get the knack

and it is key to getting an even coat. Try to keep your coating to a defined area, and not just all over the place, Work to

an area larger than the desired print size but inside the paper dimensions. Throughout the coating, roll the coat

methodically so that all parts of the area get equal treatment from the roller, not just the middle.

Start to roll down hard onto the substrate then slowly lighten the pressure until you are only just supporting the handle.

When you begin to coat you should be firm and apply as much pressure as needed to gain the initial evenness and

define your coating area. By the time you are coming to the end of the coating procedure. The only pressure should be

the weight of the roller handle resting in your hand. Take your time. Let the coat just relax onto the substrate. By the

time you are coming to the end of the coating the roller should be moving much faster, as if you were just lightly

polishing the surface. Directly the coat looks even, stop rolling. If all has gone well, you will end up with a smooth

eggshell like finish that will expose well.

10Issues and Problems

Beware of handling the Yupo/substrate too much; wash your hands first so that you do not transfer any grease

from your hands to the substrate. If grease does get on to the Yupo/substrate when you come to lay your first coat you

will get clearly defined fingerprints and patches where the coat will refuse to take. This can be repaired, by

scrubbing the offending spot with the roller until the coating mixture is no longer repelled by the substrate. In the long

term this is not really a problem as it rarely persists to the second coat, However it maybe an indication that things

could be more tightly controlled.

Sometimes beginners experience problems with their first coat that appears blotchy. This is due to the fineness of

the surface and the thinness of the coating and is normal.

In this respect the viscosity of the mixture is critical. If it is too wet you get bubbles that will denigrate into big

blotches and if the coat is too viscous you get little white specks that also give similar unevenness problems. To solve

the former, deplete the roller on a paper kitchen towel or clean news print paper. Then pass the hot hair dryer over the

coat a few times to stiffen up the coat, and re-roll. To solve the latter throw away the mix, remake and roll over again.

Do not try and let down the mixture by adding fresh emulsion.

As part of the process you will get a pronounced texture on the first coat. This is the footprint of the foam roller, which

will disappear with subsequent coating. To obtain a texture free coat, first time is very difficult. So multiple

coating is essential. However in practice this does not pose a problem, as the coats dry very quickly. The process of

building up the image in this manner is very satisfying it puts you in charge. Not the process, this is one of the great

joys of Temperaprint.

Another problem associated with rolling technique is when you get bars of lighter density appearing in your coat.

These bars can be horizontal or vertical to the direction of the roller. The cause is going outside your defined coating

area compounded by not rolling in one direction in the early stages. You are allowing the roller to go off the

coating area and onto the uncoated surfaces. This has a direct effect on the roller as these surfaces now take some of

the emulsion from the roller, which in turn takes it from the part of the coat you want, i.e. from within the print area.

You will notice that the distance between the bars is the same as the circumference of the roller, which is a sure

indication that this is the problem.

What upsets and effects the students at the School of Temperaprint are minor imperfections in the preliminary coats

coursed by, dust, bits of hair, and other debris. One of the major causes that has contributed to this problem has been

what the students are themselves wearing, where fibres from their own clothing can get on to the coating surface.

Awareness of this problem and a clean working environment will certainly substantially alleviate, if not completely

eliminate these problems.

However it must be born in mind that the process is self-healing. As the multiple coating proceeds, students find that

these defects magically disappear as the further coats heal the perceived defect until it is no longer noticeable in the

print. That perceived defect just seems so much more important when it is the only mark on the paper, in the first

coat!

11Drying

Once you have finished laying the coat you will need to dry it prior to exposure. To do this, apply a stream of warm

air over the surface at the finish of the coating process. This is most conveniently achieved using a hair dryer. When

you come to this part do not hold the hair dryer over a single spot, keep it moving. If heat is applied to a single spot

you run the risk of heat fogging which needless to say is something that could ruin a print. Keep the hair dryer

moving at all times and at least nine inches away.

The Yupo/substrate has no fibre to hold moisture so that the only moisture present is in the actual thin emulsion layer

that you have applied. It will only take a few moments, at most a minute, for this coat to dry. You can tell when dry

by the surface sheen, which turns to an eggshell matt appearance. To test if the coat is actually dry, turn the hair dryer

on to your free hand to drive off any moisture and then lightly run your hand round the boarders of your print. That

way if it is still tacky you have not disturbed the main part of the coat that you want to keep. Once the coat is dry you

are ready to make the exposure. Remember the coating is much more light sensitive when dry. It is a good idea to

have a separate clean workspace dedicated for this purpose. Remember DON’T OVERDRY. Otherwise a heat fogging

will spoil the print.

12Exposure

Contact printmaking

NEED

As previously stated, Temperaprint is by its nature very insensitive to light. Herein lies both the strength and

weakness of the process. Contact printing is the only feasible method. Although there are heroes who spend

hours printing by projection in our opinion, life is just to short to travel down that path. However they’re many

advantages to contact printing. The method is mechanically faster than most the projection technique. It is possible to

print several negatives at the same time, and contact exposure once assessed, will tend to remain constant.

The main disadvantage is that to make a reasonable sized print, a negative of the same size is also needed, and as

most of contemporary photographic image making is centred around small format negatives. Some form of enlarged

duplication will needed.

13Large format

The prime requisite will be a large format negative that is the same size as the resultant print. This aim can be

achieved in a number of ways, as the Chinese say there are many paths to heaven not just one. We at the School of

Temperaprint now concentrate on the production of positive digital files that we then enhance electronically, and

output as printers in either negative or positive separations via the computer and print onto inkjet film.

Alternative non-digital methods are also possible, for those not conversant with or sympathetic too digital imaging and

control.

14CONTACT PRINT MAKING

Registration

Need

At the heart of any multiple printing lies the problem of registration. Temperaprint is no different, fortunately our

yupo/substrate is dimensionally stable so half the problem is solved.

Methods

There are many methods of registration that are used in printmaking and industry. The most common and reliable is

thepin register system. This is a method where the printers are punched with a series of holes that are in the same

place on each of the printers. The paper that you are going to print onto is also punched and the printers are attached

using special pins that fit the holes perfectly. The joy of this is that the pins will ensure that the printers always go back

in exactly the same place each time with out the need to visually line them up, as all the registration is carried out in

the initial punching phase.

The problem with this is that these systems are professional and can be prohibitively expensive. An inexpensive

version of this system can be constructed using a four-hole office punch that is a fraction of the cost of

the professional versions. Unfortunately these punches are not standard in the size of the hole that they produce

and there are no pins on the market to cater for them. A way that has been found to deal with this problem is to use

double-sided tape and stick two or three layers of Yupo/substrate together with a further strip of the double-sided tape

on one side. These pieces of layered yupo/substrate are then punched to produce round punched pieces, these

punched round pieces are then attached to a further slightly larger piece, say about three-quarters of an inch or two

centimetres in diameter.

This can produce a cheap and relatively easy way of solving the problem Though not completely perfect you can make

many of these home made pins, so that if they fail, as some will, it will not matter as you will have many more as

spares. A bonus if you have a problem with miss-laying things in a working studio. Some stick on rubber or plastic tiles

can also be used in a similar manner.

15Contact Frames

For a contact frame there are many that are supplied from photographic manufactures that are perfect for the job. The

best type of contact frame is a vacuum frame where the air is removed using a pump. This results in an even

contact across the whole print area and ensures that all the detail that is in the printer has a chance to be exposed

accurately. Again the problem is that this is a professional piece of equipment an as such commands a professional

price. A simple and easy type of frame to make consists of at least four strong clips, a sheet of glass, and a piece of

board cut to the same size as the glass and some thin foam. Make a sandwich of the board, foam, yupo/substrate

printer and place the glass on top. Now put the clips around the edges and they should squeeze the glass and the

board together, thereby giving you the contact you need. This is a very rudimentary way of achieving a form of contact

frame. A more precise method is to construct a pneumatic version known as the litestar frame as explained in the

advanced chapters

16Ultra Violet light Sources

Now that you have your coated paper and printer prepared, it is time to expose it to a light source rich in ultra Violet

radiation. A number of light sources are employable, but most are too weak for this process. A cheap and

convenient source is a sun bed, particularly the small facial or half size torso type that can be purchased at quite

reasonable prices.

It is important to remember that ultra Violet light is a harmful form of radiation and as such should be contained even if

it is a sun bed which has been designed for tanning skin. The other source of useful light, which is readily available, is

direct sunlight. This can be used, but you will have to deal with the vagaries of the weather and the time of day. A

further source is a plate maker or silk screen lamp such as is used in industry. These sources can be very dangerous

and you should always confer with the suppliers on its containment and use.

Of all the sources the simplest and most convenient is the sunbed. You should be able to purchase this through mail

order, or if you are living in the more northerly climates you may find one in a local store or second hand shop. The

good thing about sunbeds is that they are consistent, repeatable and can be used with the flick of a

switch; a major consideration in a multi-coat system such as Temperaprint. To use a sunbed place it face down on

supports at each end leaving a gap underneath for the contact frame to be slid in and out. You can place a piece of

fabric along the edge of the gap to contain the light but do not cover any heat vents. Exposure should be made at a

distance of three to six inches. If the coating has been carried out correctly. The time exposure should be in the order

of three to five minutes; you will need to test this for yourself. Which is only a case of making a series of controlled test

exposures to find an optimum time. Darker colours may require a slight increase in exposure while thinner lighter coats

may require slightly less. Familiarisation with the process will come after making many coatings, and you will in time

be able to see how to make these slight adjustments instinctively.

17Wash off Environment Tools

Sink with running water Paint pad Washing-up liquid Sponge Small brush Two photographic flat bottomed dishes, one with a cover 1% sulphuric acid Glass sheet Plastic or rubber apron Protective gloves Tongs Eye shields

Ensure that the washing off area has everything in place. There should be running water, preferably with a hose so that

you can direct the water where you want it. Place in or next to the wash area a bowl with water, containing a “squirt”

of washing-up liquid, in which you can place the paint pad, brushes and sponge. The glass sheet is to lay the print on

during the development of the coat. It is important that the surface you use for the wash off is flat and not uneven

because when you remove the unwanted portions of the coat, any irregularities in that surface will result in uneven

development. Depending on your own individual circumstances and preferences you may find it more comfortable to

work in an upright position in which case ensure that the glass sheet is propped up at a suitable angle inside the wash

area and is not liable to slip. You may find that you prefer to work flat and have the room to lay the sheet down in the

wash area. The choice is not a critical one but should be made according to comfort and ease. This is a multi-coat

system and you will return to this area time and time again.

There will need to be a provision for the 1% sulphuric acid clearing bath. This bath at the specified dilution is not

dangerous. However it is sensible to place in a position, that easily disposed of when finished with. Ideally this should

be either in the washing area so that splashes and drips are contained and easily washed away, or directly adjacent to

it so as there is minimal handling of it in when in use.

The function of this bath is to remove the residual dichromate stain, which if not removed, will degrade the

colours of the print giving them a orange brown cast, in monochrome this is of no matter, but in fine colour work it is

essential to remove this troublesome caste.

18Developing the Coat

Now that you have prepared the area and completed the exposure the next phase is to remove those parts of the

image that have received no exposure. After you have removed the print from the exposure unit and taken off the

printer, place the print in a tray of water to remove the now unwanted sensitizer. This soaking phase will still need

to be carried out under subdued lighting. You will notice that the water turns yellow.

This is the Ammonium Dichromate being released from the coating and dissolving into the water. The importance of

this is that the coating layer will no longer be sensitive to light. This means that once it has had a one minute soak you

can take the print out into a full light situation to complete the washing phase of the print without any danger to the

print.

Place the print on the glass sheet and wash with running water to remove any sensitizer that remains.

Take the paint pad and place it flat to the surface of the print and in a gentile circular motion begin to remove those

portions that are still soluble. As you are doing this, do not press, let the pad glide over the surface of the print by is

own weight do not press down In this way the pad is very gentile and will produce an even development if done

uniformly.

Work across the whole image area in a methodical manner so that all areas get equal treatment. From time to time

play the water across the surface so that you can see any area’s that have been missed and are not there for being

fully developed. Wash some areas a little less if you want to retain more of the coat or a little harder if you wish to

retain less. Be careful not to lift the pad on to an edge or corner, this will result in a more abrasive effect on the coat

and will produce an uneven development. A brush can be used creatively to remove coating in precise area’s if

required. It will be more abrasive than the pad. Having the benefit that you can tackle individual elements of the image

in greater detail giving a more painterly approach to the manipulation of the image than just using the pad alone.

A sponge can also be used to remove the coating gently instead of the pad. Being able to tackle more specific

areas. Though not as precise as the use of the brush it does allow you to scumble the coat in a similar manner as

painters treat a glaze coat, also the application of a small amount of cream abrasive can be effective. However do not

use hash powder type such as Vim. What is needed is a gentle cream abrasive the type that is used to clean plastic

baths. With these abrasives it is possible to obtain very subtle graduations of colour and tone.

19Clearing Bath

The clearing bath is used to remove the residual dichromate stain that is left after the print has been developed.

The bath consists of a dilute solution of Sulphuric acid i.e. 1% great care must be taken when this is initially made up.

Once you have completed the wash off phase to your satisfaction place the print into the bath. A yellow tint

will become apparent within the bath; this is the residual stain being removed. The clearing will only take about a

minuet to complete. This stage does not need to be carried out after every coat and can be either left to the end of the

printing, or done at any chosen point when you wish to check for colour balance.

With monochromatic images using just earth colours you may omit this stage if you wish, as the stain is a compatible

colour so the clearing will predominantly have a lightening, rather than a chromatic, effect.

Once the print has cleared remove it from the bath and wash.

Final wash

Once cleared the print needs a final wash to get rid of any residual clearing bath that may interfere with further

printmaking.

20Dry

Now dry the print keeping the hair-dryer moving at all times, or just hang it up to dry. The Synteape/Kimdura/Yupo

has no paper fibre so it will dry quite quickly. You may blot the surface to remove the bulk of the water using J cloths or

other similar non-fibrous material but be careful the surface emulsion is quite delicate until it has fully dried.

Conclusion

When you have reached this point you are ready to re-coat the print. Further colour layers will increase the richness of

the print but you must be aware that if you continue to coat beyond a certain point, the print will begin to darken.

Artist colours, in common with all paints work by the subtraction of light, so further coats will have the effect of taking

more of the reflected light away. Again this is a matter of experience and cannot be prescribed in advance. You are

now ready to return to the coating stage. The coat that you have printed is now quite firmly attached to the substrate

and will not be removed by further coating.Happy printmaking!

Patterning the World: The Rise of Chemically Amplified Photoresists

In the late 20th century increasingly powerful and numerous personal computers and interconnected networks thereof were at the center of shifts in work practices, communications, and cultural production that collectively became known as the digital age. These personal computers were in no small part defined by two key types of electronic components: the microprocessor and the dynamic random access memory (DRAM). These components in turn were both species of silicon integrated circuits, owing both their existence and their growing power to new developments in the manufacturing technology used to create them. Computer chip manufacturers in the mid-1980s were pushing the limits of miniaturization using a variety of innovative manufacturing practices. The rise of the digital age depended on new materials and techniques that could both increase performance and drive down cost

For decades the semiconductor industry had used photolithography to build integrated circuits on wafers cut from large single crystals of the element silicon. In the patterning process of photolithography, a polymer film called a photoresist is deposited over a thin film of one of a variety of materials deposited atop a silicon wafer. Next, in a complex (and expensive) apparatus known as an exposure tool, light of a very specific wavelength is projected through a pattern-bearing mask onto the photoresist. Regions of the photoresist exposed to the light undergo chemical changes, making them either more or less susceptible (depending on the process) to being removed in a subsequent chemical developing process. Thus the pattern of the mask is transferred to the photoresist. The pattern from the photoresist is then transferred to the underlying thin film through a subsequent process of chemical etching. Multiple iterations of this thin-film patterning process, along with several other physical processes, produce integrated circuits. The photoresist is at the center of the photolithographic process, just as film used to be the crux of photography.

In the late 1970s photolithographic procedures used light from the near-ultraviolet (UV) and mid-UV ranges at 365 and 313 nanometers (nm), respectively. Manufacturers realized that moving to a shorter wavelength, the so-called deep UV, at 248 nm or less, would allow even smaller patterning of integrated circuits, thereby continuing the dynamics of miniaturization, exponential increases in functionality, and dramatic decreases in cost that characterize Moore’s law. Making the leap to deep UV would require dramatic materials innovations and a sea change in photoresist technology. An entirely new breed of photoresist—chemically amplified (CA) photoresists—created within IBM in the early 1980s for just this purpose would eventually come to dominate global semiconductor manufacture. More recently, a later generation of chemically amplified photoresists tuned to 193-nm light has continued to enable Moore’s law. For nearly two decades CA photoresists have stood behind the digital age, largely unrecognized and undeservedly so.

Pushing the Limits at IBM

Some commentators describe the digital computing business in the late 1970s as divided into halves, with IBM on one side and all the other companies on the other. Despite thriving competitors in the minicomputer business and the appearance of the very first personal computers, IBM dominated the computer industry with its broad offering of mainframe and mid-range computer systems, largely produced by captive suppliers within IBM. Large semiconductor fabrication operations in East Fishkill, New York, and Burlington, Vermont (among other locations), produced integrated circuits as logic and memory components. Many of the materials for these semiconductor fabrication plants, or “fabs,” came from additional operations in East Fishkill. In San Jose, California, a disk-drive manufacturing facility boasted a research laboratory. On the East Coast, Yorktown Heights, New York, was the site for the firm’s research and development headquarters.

Throughout the 1970s IBM produced its own photolithography equipment. As the decade drew to a close, however, IBM began to purchase significant numbers of sophisticated and expensive optical devices from the outside, particularly the Micralign lithography tools produced by the venerable optics house and chemical-instrumentation manufacturer PerkinElmer. IBM’s production facilities for advanced semiconductor components contained hosts of self- and PerkinElmer– produced lithography “tools.” These

capital goods represented an enormous expenditure, with each tool having cost hundreds of thousands of dollars. In the same period, the fate and future utility of these existing tools were being seriously questioned within IBM.

By the time the 16K DRAM generation was launched in 1977, semiconductor memory was well on its way to displacing magnetic core memory as the dominant memory technology for digital computers. DRAMs were considered the shining examples of so-called large-scale and even very-large-scale integrated circuits in which huge numbers of components were squeezed onto tiny chips of silicon using the latest manufacturing technology, yielding expanded memory functionality at declining costs. Magnetic core memory, in contrast, hailed from the 1950s and consisted of great grid-like planes of wires with small metal rings at each intersection: think of the screen in a window, with a miniature washer around the corner of each little square. The magnetic states of these rings, or “cores,” represented the digital language of zeros and ones. First introduced in 1970, DRAMs were beating out cores on both performance and cost just six years later.

The success of DRAM depended on the semiconductor industry’s ability to push its manufacturing technology to the limits. Indeed, DRAM production became the bellwether for such technology. The semiconductor industry, led by Intel, had established a metronomic pattern in which the industry launched a new generation of DRAM with four times the capacity of the previous generation—1K, 4K, 16K—every three years. Each generation required a new level of miniaturization, thereby creating a fundamental link between DRAM generations and manufacturing technology.

In 1977 a looming question for the semiconductor industry was whether or not the existing lithography tools for the 16K DRAM generation could be used again for the upcoming 64K DRAM generation or perhaps even for the 256K DRAM generation. The ability to form smaller features depended on the wavelength of light used in the tool: the smaller the wavelength, the smaller the possible features. The existing lithography tools used 365 nm light in the near-UV region to expose patterns onto silicon wafers coated with photoresists. Could the existing lithography tools and photoresists be modified to work with smaller wavelengths of light? The economic consequence of the answer was significant. Millions of dollars could be saved if the useful life of the manufacturing equipment could be extended.

Pausing at 313

Extending the life of IBM’s lithography tools and photoresists was a major challenge that C. Grant Willson absorbed when he joined a research group focused on polymer science and technology at IBM’s San Jose operations. Willson, a Bay Area native, had earned his Ph.D. in organic chemistry at the University of California, Berkeley, and had been working at the University of California, San Diego, doing research in biochemistry. Although it was generally recognized in the semiconductor community that significantly lower wavelengths would eventually be needed to get the required miniaturization, the San Jose polymers group was exploring the extension of near-UV lithography for upcoming DRAM generations. The IBM researchers saw an opportunity to extend the usefulness of their tools by moving to an “intermediate wavelength,” a halfway point between the current near-UV and the future deep UV.

The attraction of this intermediate step was savings: they could postpone the need to refit factories with the new tools and resists that they knew would eventually be required for the deep-UV regime. Moreover, this intermediate wavelength step—to 313 nm from 365 nm— would buy the researchers time to tackle the more radical developments that would be necessary for the eventual migration to the deep UV.

Willson’s first great success in photoresists was to develop a modified version of the standard type of near-UV photoresist, known as the DNQ-Novolac resist, but tuned to work with 313-nm light and to be compatible with existing lithography equipment. Willson’s proprietary resist was used for both 313-nm and traditional near-UV lithography and in a few short years suffused IBM semiconductor manufacturing. The resist gave IBM a competitive advantage in the form of tremendous cost savings by extending the utility of IBM’s existing tools and device performance advantages through successful miniaturization. Willson had established himself as a leader in photoresists within IBM.

By 1979 Willson was focusing on a more challenging prospect: the move to deep UV. By this time IBM was anticipating the delivery of new PerkinElmer lithography tools to its fabs—the PerkinElmer Micralign 500. This tool used a mercury lamp that generated UV radiation with intensity peaks at 365, 313, and 248 nm. The use of an appropriate filter made the tool capable of operating at any one of these wavelengths. The 248-nm wavelength was in the deep UV region, but at that wavelength the lamp emitted only 1/30 the amount of light as it did in the other UV regions. This relative dimness raised serious challenges.

Existing photoresists did not have enough sensitivity for working with such a low intensity. A work-around was possible with unprecedentedly long exposure times, but that was an economic nonstarter. Grindingly slow fabs would destroy any savings from extending the tools. The IBM researchers had two remaining options: create a new lamp for the tools that was 30 times brighter at 248 nm, or invent a photoresist that was 30 times more sensitive to 248-nm light than the DNQNovolac resists.

A Chemical Solution

Willson focused on the chemical challenge: could he create a new photoresist with 30 times the sensitivity? Willson discussed this situation with a visiting scientist who joined his group in the first days of 1979: Jean Fréchet. Fréchet, born in France, was an accomplished polymer chemist on sabbatical at IBM in San Jose from the University of Ottawa. In discussions between Willson and Fréchet the essence of the needed innovation emerged: chain reactions. They imagined a photoresist in which a single photochemical event—the absorption of a photon by a material in the resist—could generate a cascading chain reaction. The chemistry of the photo-resist would amplify the effect of the photochemical event, yielding the great sensitivity that was their goal.

Fréchet quickly advanced a particular polymer as a possible candidate for use in such a system: polyphthalaldehyde (PPHA). This polymer chain is unstable at room temperature; its propensity is to unzip, to depolymerize. The only way to stabilize the polymer at temperatures up to 200°C is to cap the chain with a chemical group. Both the polymer chain and the capping groups are highly susceptible to cleavage by acid as well. Fréchet and Willson considered the possibility that irradiation could directly break bonds in the back bone of the polymer, causing the PPHA to depolymerize. Once started, the polymer would unzip in a chain reaction.

Fréchet synthesized PPHA samples so that he and Willson could begin to work with it. By the summer of 1979, however, it became clear to Fréchet that the project could not be completed before his sabbatical ended. At Fréchet’s urging Willson made a recruiting trip to the chemistry department at the State University of New York’s College of Environmental Science and Forestry in Syracuse, where Fréchet had earned his Ph.D. There Willson met Hiroshi Ito, a research associate in the department with a Ph.D. in polymer chemistry from the University of Tokyo. Ito, like Fréchet, had experience with the special

techniques required to synthesize PPHA. Willson offered Ito a postdoctoral position in his San Jose group, and in the summer of 1980 Ito joined the lab.

Ito took over where Fréchet left off, beginning by synthesizing PPHA by new means to produce a more temperature-stable polymer. Ito irradiated his PPHA, and the result was more a fizzle than a chain reaction: there was depolymerization, but not enough. Ito’s next move was to mix a well-known photoacid generator (PAG) into his PPHA and expose the mix to deep-UV light. PAGs are compounds that generate acid when exposed to light. Since both the PPHA chain and its capping group could be cleaved by acid, Ito thought the PAG might initiate the desired chain reaction. This time half of the PPHA unzipped. This was far better but still not good enough.

Meanwhile a new class of PAGs based on onium-salt compounds had recently emerged from both 3M and General Electric. These onium-salt PAGs produced notably strong acid, and many had the added virtue of stability at high temperatures. The potential of these new PAGs for polymer chemistry was broad, and the PAGs quickly generated interest. Remarkably, Willson learned about the 3M PAGs at almost the same time that Ito alighted upon the General Electric PAGs. Ito had been searching for another PAG to add to PPHA—one that was more temperature-stable and produced stronger acid than the traditional PAGs. At General Electric the chemist James Crivello had invented triphenylsulfonium hexafluoroantimonate (TPSHFA) for UV-induced polymerization, or “curing,” of epoxy resins. This onium salt generated a strong acid that catalyzed the polymerization. Ito hoped that in his PPHA photoresist system, the onium-salt PAG would initiate a strong chain reaction of unzipping.

Willson vividly recalls the day when Ito first tested his novel mixture of PPHA and Crivello’s PAG as a deep UV photoresist. The results, Willson recalls, were “remarkable.” With the new onium-salt PAG and a dose of UV light 100 times less intense than that used in conventional photolithography, the PPHA rapidly and fully unzipped. Not only did the materials unzip, but the exposed regions of Ito’s mixture also completely vaporized, laying bare the underlying substrate. Ito’s material was a dramatic proof of concept of the chemical amplification scheme that Willson and Fréchet had advanced the previous year. At hand was a material with high resolution (the ability to produce fine patterns), high speed, and tremendously improved sensitivity to deep-UV radiation. Yet Ito’s PPHA system worked too well and not well at all. The vaporized photoresist material would hopelessly contaminate the lithography tools. Further, PPHA’s susceptibility to acid meant that it could offer little protection from acidic etching procedures and hence would be of little to no use in actual device fabrication.

Willson and Ito turned to another polymer that Fréchet had worked on earlier at IBM San Jose during his sabbatical there in 1979: poly(p-hydroxystyrene), or PHOST. PHOST is a styrene-based polymer, chemically similar to the Novolac resins used in conventional photoresists. Willson suggested modifying the polymer to include a new side chain: tertiary butoxycarbonyl, or tBOC. The resulting polymer was poly(p-t-butyloxycarbonyloxystyrene), or PBOCST. Willson, who had worked mainly in biochemistry before joining IBM, was aware that tBOC—a mainstay in peptide work—was susceptible to cleavage from the basic polymer through the action of both heat and acid. Willson and Fréchet recall early, inconclusive attempts by Willson and several coworkers to make a PBOCST resist based on acid-catalyzed cleavage of the tBOC groups using photosensitive orthonitrobenzyl esters to produce the acid. From Ito’s perspective the PBOCST work was dormant when he reached the lab. However, Ito also began investigations of photoacid-catalyzed cleavage of a different tBOCprotected polymer as a potential basis for a chemically amplified resist. Looking at Ito’s results, Willson and Ito decided to pursue a hybrid course: mixing PBOCST with the

onium-salt PAG. The result of this mixture—the brew resulting from the experiences and interests of Fréchet, Willson, and Ito—stopped the researchers in their tracks.

The tBOC resist displayed dramatic chemical amplification. After exposing the tBOC resist to 248-nm deep-UV light, the resist-coated silicon wafer was heated in a post-exposure bake. The acid generated by the onium salt catalyzed the cleavage of the tBOC groups. The resulting fragments then generated additional acid, catalyzing further tBOC cleavages in a cascade of de-protection. The reaction was both extremely fast and extraordinarily sensitive to the deep-UV light. At the beginning of his search for a CA resist Willson knew that he needed a 30-fold improvement in sensitivity over conventional resists. With the tBOC resist, Willson, Fréchet, and Ito had generated a 100- to 200-fold improvement.

By 1983 Willson was confident enough in the new tBOC resist to promote it within IBM. At East Fishkill he presented it to a collection of researchers and engineers from a variety of IBM sites, including representatives from East Fishkill’s own photoresist operation and staff from the cutting-edge fab in Burlington. John Maltabes, a lithography engineer from the Burlington plant, had been helping develop a manufacturing process for a 1M DRAM using deep-UV radiation to meet a “1 micron design rule.” Deep-UV lithography would be used to produce features as small as 1 micron on the new powerful memory chip. Maltabes had been evaluating the possibility of replacing the mercury lamps within the PerkinElmer lithography tools in Burlington with excimer lasers. But Willson’s tBOC presentation persuaded Maltabes that using the new photoresist with the existing mercury lamps was the better strategy: when he returned to Burlington, Maltabes tried to convince his supervisors to kill his project. Three months later they did just that. Maltabes’s new job would be to help implement the tBOC resist for manufacturing the 1M DRAM.

Something in the Air?

IBM had staked the future of its cutting-edge products on CA photoresists. The advantages were tremendous: the tBOC resist could save IBM millions of dollars in modification and replacement of its existing lithography tools. The downside was the uncertainty that the new resists would work in an active manufacturing environment.

Production trials at Burlington, however, revealed new, unanticipated problems with the CA resist. For one, its sensitivity varied widely. After eliminating the lithography tools as the source of this unpredictability by installing new, exacting filters, the blame rested squarely on the tBOC resist. Eventually, the production engineers in Vermont resorted to the kind of highly empirical “black magic” practices that characterized much of semiconductor manufacturing in its early years. They did not know why certain things worked, only that they did. The engineers found, for instance, that letting silicon wafers that had been coated with the tBOC resist sit for several hours in the factory before exposing them stabilized the sensitivity, but at a lower level.

More troubling was the occasional formation of “skins” in the uppermost layer of the tBOC resist. These skins were regions of the photoresist in which sensitivity had catastrophically collapsed. Exposed regions of the resist near the surface would not develop properly and thus formed a skin that could not be removed by the solvent. Puzzlingly, these skins were all at the surface of the resist. Regions of the resist directly below these skins developed perfectly. The issue was serious: these skins would result in fatally defective DRAMs.

The groups at San Jose, Burlington, and East Fishkill were troubled by the new resist’s difficulties. Maltabes recalls a lunch conversation in San Jose about these issues in which a researcher who had experience manufacturing disk-drive systems suggested that these troubles stemmed from “something in the air.” This researcher and his colleagues had attributed certain failures of disk-drive systems to airborne contaminants and had used air-filtration systems with activated charcoal and HEPA filters to get around the problem. Surplus filtration units sat in a warehouse, and he offered them to the tBOC team.

Maltabes and Scott McDonald from Willson’s team returned to Burlington with the surplus units. With a series of experiments the pair determined that in filtered-air environments, and indeed environments of air pumped in from outside the fab, the skins disappeared and the resist sensitivity was both high and consistent. The atmosphere of the fab itself harbored contaminants that were responsible for the problems with the tBOC resist. With pressure mounting to get the 1M DRAM into full production, Burlington decided to filter the air rather than hunt down the unknown contaminant or contaminants. Once wafers were coated with the tBOC resist, they remained in a filtered-air environment until they entered the lithography tool.

By 1986 1M DRAM production was in full swing. IBM manufactured several million of these DRAMs, all dependent on the CA tBOC resist. Reflecting the criticality of tBOC resists to the success of this project in moving IBM to the first deep-UV manufacturing technology, the firm kept the tBOC resist as a proprietary material and the use of filtered air as a closely held trade secret into the early 1990s. Several million working DRAMs within IBM’s flagship computer products offered powerful testimony: the era of CA photoresists had arrived.

Coda

For IBM, possession of the first CA photoresist conferred significant competitive advantage. By the mid-1990s, however, a combination of accidental and systematic factors broke IBM’s exclusive hold on this class of material. Willson, Fréchet, and Ito had patented the tBOC resist in 1982, but the patent was limited to just the tBOC material, not the very idea of a CA photoresist. This limited scope was the product of multiple factors: the large role played by the researchers rather than attorneys in writing the patent; the vagaries of process patenting in comparison with patents on particular materials; and the discovery of “prior art” in the patenting process. One of the developers of onium-salt photoacid generators at 3M, George Smith, had previously patented a photoresist involving a very similar mechanism to the tBOC resist. These accidental factors allowed commercial photoresist producers—inspired by IBM’s success— to bring their own versions of CA deep-UV resists to the market by the early 1990s.

More systematically, CA photoresists escaped IBM as the computer giant participated in the growing trend among semiconductor manufacturers to obtain manufacturing equipment and materials from specialized external suppliers. As IBM came to rely more heavily on lithography tools produced by outsiders, the close coupling of tool with resist meant not only that the tool makers would need access to the best CA resists but that the tool makers’ other customers would also require access. Moreover, specialized photoresist houses had greater resources and incentives for pushing CA photoresists forward. In the mid-1990s IBM actively transferred the second- and third-generation CA photoresists developed by Ito and others to the outside world. In doing so, IBM accelerated future developments in CA resists, empowering the continued evolution of the digital age.

David C. Brock is a senior research fellow with CHF’s Center for Contemporary History and Policy and the editor of Understanding Moore’s Law: Four Decades of Innovation (CHF, 2006). The author wishes to thank CHF’s Gore Innovation Project for the support of the research leading to this article; Hiroshi Ito, C. Grant Willson, John Maltabes, and William Brunsvold for their time and candor in a series of research interviews; and Christophe Lécuyer for his revealing oral history with Jean Fréchet.

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