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© Boardworks Ltd 20051 of 21

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Graphic ProductsPrinting


Learning objectivesL

earn

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ob

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the different printing methods available

four colour process printing

the printing effects that can be applied to printed products

quality checks that are performed on printed products.

To learn about:


Graphic products can be printed in a variety of different ways. The designer has to select the printing process that suits their product best.

This will depend on the length of the print run, the quality required, the paper or card needed, and the project’s budget.

The designer will choose from the following printing methods:

Printing methods

letterpress

lithography

flexography

gravure

screen printing.


Letterpress

Letterpress is one of the oldest forms of industrial printing. Letterpress is known as a relief printing method, because the printing plate is not flat.

A printing plate is prepared with the image to be printed raised above the surface of the plate, standing proud of the non-printing area.

The raised surface is coated with ink and is then pressed onto the paper.

It is an expensive process, as the plate has to be specially made and high quality paper is needed. It is used for high quality books and stationary.

Printing methods


Lithography

Lithography is the most commonly used process in the printing industry.

The image is transferred onto the completely flat printing plate photographically, using UV light.

The plate is washed in a chemical that makes the image area attractive to the oil-based ink. The non-image area is dampened with water to repel the ink.

Lithography is used for medium to large print runs because the set-up costs are high.

Printing methods


Flexography Flexography is very similar to letterpress as it uses a relief plate. As the name suggests, the relief plate is made from a flexible material, like rubber.

It is used to print on unconventional materials, like polythene for packaging. Flexography is ideal for these surfaces, because the ink is mixed with a solvent that evaporates, causing the ink to dry quickly.

Flexography is used on carrier bags and some wallpapers.

Printing methods


Gravure

Gravure is used to produce high quality photographic images. It is very good for reproducing fine detail. However, gravure is a very costly process due to the skill needed to manufacture the printing plate.

It is the opposite to letterpress – the printing areas are in fact lower then the non-printing areas. The image is engraved onto a copper plate, creating cells that are filled with a spirit based ink. The paper is pressed against these cells to produce the image. The ink evaporates quickly once printed.

Printing methods


Screen printing

Screen printing is completely different to any other printing method. It works by forcing ink through a stencil. The stencil shape reflects the image to be printed. The stencil can be made of paper or card and is supported by a fine mesh.

The ink is spread over the mesh using a spreader, and then forced through the mesh onto the surface to be printed. Stencils can be made fairly simply, but to create more complex images, a photographic stencil is required. These have to be made by a professional or using a computer.

Printing methods


Other printing processes

Material Commercial printing processes

Plastics Paper labels – lithographic, gravure, letterpress, screen printingShrink sleeves – as aboveDirectly onto plastic – heat transfer labels, gravure, screen printing, dry offset

PVC shrink sleeves Gravure – reverse printedFlexographic – reverse printed

Glass Onto paper labels – lithographic, gravure, letterpress, screen printingOnto polypropylene labels – as aboveDirectly onto glass – ceramic decoration

Metals On to paper labels – lithographic etc.Directly onto metal – dry offset print, reprotherm

Solid board Litho, flexographic, Screen printing, Gravure

Foil/film laminates Flexographic, Gravure


Printing methods


Guillotines can be used to cut straight edges on batches of card and paper. Die cutting is used when the shape is irregular.

A blade similar to that of a cookie cutter is made, and the design is stamped out. This can be done by hand or using a hydraulic press.

Folds are created in a similar way, except that the blade does not cut all the way through – it creates a crease instead.

Die cutting and folding


You can add interest and impact to a graphic product by adding a printing effect. There are lots of printing techniques to choose from, but they can restrict your choice of materials and add to the final cost.

The designer can choose from the following printing effects:

Printing effects

Embossing

Laminating

UV Varnishing

Spirit Varnishing


Applying varnish to a product has two main functions:

Printing effects

Varnishing

Varnishing is done after printing but before any cutting, folding or trimming.

There are several different types of varnishing. Oil-based and water-based varnishes are sometimes used, but the most important types of varnishing are spirit varnishing and ultraviolet varnishing.

to protect the product

to make the product look better.


Spirit varnishing involves applying a spirit-based coating to the product to produce a high-shine finish.

It is relatively cheap, but the ink must be completely dry before the varnish is added, making the manufacturing time longer.

Printing effects

Ultraviolet varnishing involves applying a thin coating of liquid plastic, and then hardening it using UV radiation.

It gives a tougher, glossier finish than spirit-based varnishing, but is more expensive. It cannot be added until the printing ink is completely dry.

UV varnishing

Spirit varnishing


Laminating (or encapsulating) produces a tough, high gloss finish.

The image is sealed between two layers of plastic. It is twice as expensive as varnishing, but the end result is of a lot better quality.

Lamination is used for products like menus that need to be easily wiped clean.

Printing effects

HOT LAMINATE

COLD LAMINATE


Embossing is when a portion of the surface is raised above the surrounding area. It is used for two reasons:

The required shape is pressed into the work using a steel die.

Printing effects

visual impact

add texture

Embossing can give an expensive, high quality feel.


Printing effects


To reproduce a full colour image or document, commercial printing companies use what is called ‘four colour process printing’.

The four colours are called the ‘process colours’. They are overlaid to produce the full range of colours. The process colours are:

Process colours

The image is separated into the four process colours, and a separate printing plate is produced for each. This is known as ‘colour separation’.

CyanCyan

BlackBlack

YellowYellowMagentaMagenta

These colours are known as CMYK.

Black is represented by the letter K so it is

not confused with blue.


This image shows the colour separation for the picture in the top left hand corner.

Process colours


Quality is essential in all products – printed products are no exception. When a document or item is printed, a series of marks are created that allow manufacturers to check that the printing has been done correctly:

Registration marks

These marks allow printers to check alignment. If the colour plates are aligned properly, the mark will appear black.

Quality checks

Colour blocks Allow you to check the colour for correct tone and equal density.


Plenary


Key pointsK

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There are many different printing methods available, including letterpress, lithography, flexography, gravure and screen printing.

Die cutters and creasing bars are used to cut out shapes and create folds accurately.

You can add interest and texture to graphic products by varnishing, laminating or embossing them.

Commercial printers usually use four colour process printing, which involves colour separation.

Registration marks and colour blocks are used to check print quality.

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