Indigo Dye Mlv

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Indigo Dye Indigo dye is an important dyestuff with a distinctive blue color. The natural dye comes from several species of plants, but nearly all indigo produced today is synthetic. Among other uses, it is used in the production of denim cloth for blue jeans. Indigo is a frequency range of visible light, from 440 to 420 nanometers in wavelength, placing it between blue and violet. The human eye is relatively insensitive to indigo frequencies, and some otherwise well-sighted people cannot distinguish indigo from blue and violet. A variety of plants have provided indigo throughout history, but most natural indigo is obtained from plants in the genus Indigofera, which are native to the tropics. In temperate climates indigo can be obtained from woad (Isatis tinctoria) and dyer's knotweed (Polygonum tinctorum), although the Indigofera species yield more dye. The primary commercial indigo species in Asia was true indigo (Indigofera tinctoria, also known as Indigofera sumatrana). In Central and South America the two species Indigofera suffructicosa and Indigofera arrecta (Natal indigo) were the most important. Indigo is a dark blue crystalline powder that melts at 390°–392°C. It is insoluble in water, alcohol, or ether but soluble in chloroform, nitrobenzene, or concentrated sulfuric acid. The chemical structure of indigo corresponds to the formula C16H10N2O2. The naturally occurring substance is indican, which is colorless and soluble in water. Indican can easily be hydrolyzed to glucose and indoxyl. Mild oxidation, such as exposure to air, converts indoxyl to indigo.

Transcript of Indigo Dye Mlv

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Indigo Dye

Indigo dye is an important dyestuff with a distinctive blue color. The natural dye comes from several species of plants, but nearly all indigo produced today is synthetic. Among other uses, it is used in the production of denim cloth for blue jeans. Indigo is a frequency range of visible light, from 440 to 420 nanometers in wavelength, placing it between blue and violet. The human eye is relatively insensitive to indigo frequencies, and some otherwise well-sighted people cannot distinguish indigo from blue and violet. A variety of plants have provided indigo throughout history, but most natural indigo is obtained from plants in the genus Indigofera, which are native to the tropics. In temperate climates indigo can be obtained from woad (Isatis tinctoria) and dyer's knotweed (Polygonum tinctorum), although the Indigofera species yield more dye. The primary commercial indigo species in Asia was true indigo (Indigofera tinctoria, also known as Indigofera sumatrana). In Central and South America the two species Indigofera suffructicosa and Indigofera arrecta (Natal indigo) were the most important.

Indigo is a dark blue crystalline powder that melts at 390°–392°C. It is insoluble in water, alcohol, or ether but soluble in chloroform, nitrobenzene, or concentrated sulfuric acid. The chemical structure of indigo corresponds to the formula C16H10N2O2. The naturally occurring substance is indican, which is colorless and soluble in water. Indican can easily be hydrolyzed to glucose and indoxyl. Mild oxidation, such as exposure to air, converts indoxyl to indigo.

Several simpler compounds can be produced by decomposing indigo; these compounds include aniline and picric acid. The only chemical reaction of practical importance is its reduction by urea to indigo white. The indigo white is reoxidized to indigo after it has been applied to the fabric. Indigo treated with sulfuric acid produces a blue-green color. It became available in the mid-1700s. Sulfonated indigo is also referred to as Saxon blue or indigo carmine.

Indigo is a challenging dye to use because it is not soluble in water; to be dissolved, it must undergo a chemical change. When a submerged fabric is removed from the dyebath, the indigo quickly combines with oxygen in the air and reverts to its insoluble form. When it first became widely available in

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Europe in the sixteenth century, European dyers and printers struggled with indigo because of this distinctive property.

A preindustrial process for dyeing with indigo, used in Europe, was to dissolve the indigo in stale urine. Urine reduces the water-insoluble indigo to a soluble substance known as indigo white or leucoindigo, which produces a yellow-green solution. Fabric dyed in the solution turns blue after the indigo white oxidizes and returns to indigo. Synthetic urea to replace urine became available in the 1800s. Another preindustrial method, used in Japan, was to dissolve the indigo in a heated vat in which a culture of thermophilic, anaerobic bacteria was maintained. Some species of such bacteria generate hydrogen as a metabolic product, which can convert insoluble indigo into soluble indigo white. Cloth dyed in such a vat was decorated with the techniques of shibori (tie-dye), kasuri, katazome, and tsutsugaki.

Two different methods for the direct application of indigo were developed in England in the eighteenth century and remained in use well into the nineteenth century. The first method, known as pencil blue because it was most often applied by pencil or brush, could be used to achieve dark hues. Arsenic trisulfide and a thickener were added to the indigo vat. The arsenic compound delayed the oxidation of the indigo long enough to paint the dye onto fabrics.

The second method was known as china blue due to its resemblance to Chinese blue-and-white porcelain. Instead of using an indigo solution directly, the process involved printing the insoluble form of indigo onto the fabric. The indigo was then oxidized in a sequence of baths of ferrous sulfate. The china blue process could make sharp designs, but it could not produce the dark hues possible with the pencil blue method.

 Denim FabricDenim Fabrics woven of 100% cotton would be very strong and durable.Traditionally Blue Denim is warp faced cotton fabric with 3 x 1 twill construction with warp being dyed in a solid colour and weft left un-dyed. The look and quality of the Denim Fabric shall improve after dyeing, the process of which differs from plant to plant. Normally the process of dyeing dictates the technology of Denim manufacturing.

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The dyeing for Denim Fabric happens at the sizing stage. Generally there are two most popular methods of dyeing Denim Fabric. They are:o Rope Dyeingo Sheet Dyeing This process eliminates a few intermediate processes of the rope dyeing. The yarn sheet is washed with chemicals such as caustic and washing soda and after squeezing the excess water; the yarn sheet is allowed to pass through Dyeing Troughs one time for oxidation and development of dye on yarn. After dyeing, the dyed yarn is washed again with fresh water for two-three times and finalIy squeezed before allowing it to pass through 36 drying cylinders. Even today Denim Fabric without Indigo Dyeing is not called authentic Denim. Initially when Denim Fabric entered the fashion market, Denim manufacturers were using Natural Indigo Dye, which was costly and giving a natural finish. Though Synthetic Indigo Dye has gradually replaced Natural Indigo Dye, some unorganised manufacturers still prefer the latter and attract premium after branding them “Natural Dye Used”.Dyeing: The unique feature in the manufacturing of denim fabric is the dyeing of the warp yarn through a long chain Indigo Dye Range. The logs of yarns from the warping process called "ball warps" are loaded at the entry end of the range and are processed through a series of boxes which contain dye to build the shade and through boxes that rinse the yarn of excess dye. Between boxes, the ropes are exposed to air in a process known as skying, where oxidation or fixing of the dye takes place.At the end of the range, the yarn is passed over steam heated dry cans for drying. Process controls are located throughout critical components of the Indigo Range and processing is monitored and controlled. When the yarn leaves the dry cans, an in-line color monitoring system measures its shade and provides immediate feedback.

MORRISON ROPE DYEING MACHINE.              

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Features. Total length of yarn sheet in machine = 700 meterSpeed of machine = 60 meter per min (average used 25-40 meter per min)Scour box = for pre treatment and can be used for sulphur dyingSkying rollers = 35-40 rollersSkying time after every dye bath = 1-2 minutes or depend on the speed of the machineTotal number of dye bath = 8 baths Steamer = for the fixation of sulpher dyesTotal number of washing baths = 3 washing bath (2 for cold and 1 for hot wash)Total number dryers = 36 (4 TEFLON coated and 32 are stain less steel)

Usually in US Denim mills 12 – 24 ropes are simultaneously

process on the rope dyeing machine. Prior to dyeing, the ropes

are boiled out and treated with caustic-soda and wetting agent to

remove from the cotton oil, impurities which could influence the

fastness for the dye.

To dye with indigo, the ropes are immersed into the dye-bath. To

dye in rope 30 – 60 seconds immersion (20 meters yarn) and 60 -

180 seconds are required for the oxidation of the Indigo dyestuff

to ensure that also ends in the centre of the rope are equally

dyed. Please note that squeezing pressure is important 5 tons as

fastness of colour and shade depends on even squeezing

pressure. The comparatively long immersion and oxidation time

requires a comparatively expensive equipment of machinery.

In order to obtain the required deep shade of blue colour the

ropes are 5 – 6 times immersed in a sequence of dye boxes with

an oxidation range then so called skying after each dye box.

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(Indigo belongs to the group of the vat dyes which is water-

soluble in reduced solution and becomes an insoluble pigment

when oxidized.

About the author : M Bilal Tariq has worked as a Deputy General Manager

Having passed the dyeing and oxidation rage the ropes are

guided through 2 or 3 washing boxes to wash off excessive loss

pigments in the last box softener are added to ease the opening

of the ropes. They are dried in series of cans. The dried ropes

which contain 380 – 420 ends are then deposited into large

coilers Rebeaming with 300 – 380 ends per rope is easer. These

coilers are placed behind the long chain beamer where the

Rebeaming and opening of the ropes takes place. In order to

guarantee even yarn tension through Rebeaming on to a back

beam ready for sizing the ropes are guided over a tension device

which is placed approx. in 10 -11 meters distance from the long

chain beamer. Broken ends which very really happen process of

the rope are repaired at this process stage. Initially these

machines were supplied without yarn stop motion but are

available now a days on special request. This is of major

importance as lost ends, fluff, 3 – tail ends and yarn remnants can

cause inferior performance in weaving.

The so prepared beck beams are now sized in a sizing machine

preferably with 2 size boxes. The size pick up varies between 8 –

10%. In Europe mainly modified starches with binders are used,

whilst in USA certain low % of PVA is applied sin combination with

starches by some companies. Depending on the final finishing

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process (washed denim) with no filler also CMC gives excellent

performance in weaving. Special size mixes for soft denim will be

discussed separately. We recommend however not to use PVA for

sizing of denim as a surface of denim may show a leather skinned

appearance.

Process Control of Rope Dyeing for denim.

1. Concentration of HydrosulphiteIt is measured by “tytano meter”. It should be from 1.5 gpl to 2.5gpl , or by redox potential of dye bath which should be from -730 mV to -860 mV.

2. Caustic Soda or pH value

Should be from 11.5-12.5

3. Dye concentration in Dye bath

it is measured by spectrophotometer. It should be in g/l

Guidelines

High Indigo Concentration --> Shade is greener and lighterLow Indigo Concentration --> Shade is dull and Red.

High pH or Caustic Concentration --> Redder and lighterLow pH or caustic concentration --> greener and darker

Dipping Time

Longer the dipping time, better will be the penetration and lesser will be the ring dyeing effect. It varies from 15-22 seconds.

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Squeeze PressureHigh pressure will lead to lower wet pick up and result in lesser color and better penetration. At rope dyeing, squeeze pressure is 5-10 tonnes, ie. wet pick up is as low as 60%. Hardness of squeeze roller is about 70-75 deg. shores. It sqeeze rolls are too hard then there are chances of slippage and uneven yarn tension.. If squeeze rollers are too soft then shading will occur. Surface of the squeeze rolls should be ground twice a year.

Airing Time

It should be 60-75 seconds. Longer airing time results in high tension on the yarn and subsequent processes will become difficult.

Drying

Insufficient or unevenly dried yarns will result in poor rebeaming

Calculation of Replenishing Dye feed/min

Conc. of stock vat is g/l= 90range speed in yards/min=25count = 7stotoal ends = 4100

Wt of yarn dyed /min= (4100*25*1000)/(7*840*202)= 7924 gmsshade desired = 2%Amount of dye to be replenished/min= 158.5 gms

Effect of pH

At pH of 10.5 to 11.5, there will be formation of more monophenolate ions, which lead to higher color yield, as strike rate of the dye to the yarn bundle is very high, and wash down activities will be very good.

At pH higher than this, dye penetration will be less and wash down characteristics are also poor.

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Testing

1. Alkalanity in Dye Bath Liquor

Pipet 10.0 ml of vat liquor into 100ml of distilled water in a 150 ml beaker. place under continuous agitation and insert the electrodes of a pH meter caliberated at pH 7.0 with standard buffer solution.

Titrate with tenth normal HCl ( 0.1 HCl) to pH 7.0 (ml = A)

calculateg/l of NaOH = A *0.40

2. Hydro in Dye bath Liquor

Add 2 ml of 37% HCHO to 150 ml beaker. Add 2 ml of dye range liquor . Add 6 ml of 25% glacial acetic acid solution prepared by diluting 1 part acid with 3 parts water. Add 2 ml of starch/KI indicator. Add ml of water. Titrate with 0.046 N ( prepared by diluting 460 ml of 0.1 N Iodine to one liter ) solution until the color changes from emarald green to bluish purple.

G/l of hydro= mo fo 0.046N of Iodine

Importance of High Concentration of Free Hydrosulphite

The clearest shades with minimum reddish streaks are observed at by relatively high conc. of hydrosulphite. On the other side, with lack of hydrosulphite, the leuco indigo is less dissolved and thereby adheres to a greater extent to the fibres. With lack of hydrosulphite furthermore, the amount of unreduced dyestuff by oxidation at the upper level of the liquor and through activiation of unfixed dyestuff, gets separated from the fibrous material would constantly rise as the reducing agent for creating leucoform would be missing. Under these circumstances a reddish bronze like shade results due to dispersion of not reduced dyestuff in the yarn. The min. proportion of hydrosulphite should

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be around 1.3 to 1.5 gpl in case of rope dyeing and 3-4 gpl in case of sheet dyeing. Also to avoid the lack of hydrosulphite or Indigo at certain places in the immersion, vat, the whole quantity of the liquor should be circulated 2-3 times every hour.

Reaction Time

At very short reaction time, an adequate liquor exchange ( i.e. the amount of chemicals consumed and replaced by fresh addition of reduced indigo) is not assured. This has a negative influence on dyeing and depth of dye penetration. In addition to this the time available for diffusion of dyestuff until oxidation commences is too short. To ensure an even and good depth of dye penetration by dyeing in several passages, the reaction time should be 20-30 sec. for each vat (eg. at a speed of 20m/min for a reaciton time of 10 seconds, the immersion path should be maximum 3.3 meters).

A reaction time exceeding 60 seconds should be avoided as the amount of dyestuff again get reduced and released may again supersede that of additionally take up dye stuff, resulting in higher shades.

Softening Agent: 8 g/lit

Drying: Rest humidity should be 30% and then sized.

Indigo Dye Range                                                                              Sizing of yarn in Set/ Beam to Beam Position.The object of Sizing is to improve the strength of yarn by chemically binding the fibres with each other and also improve upon its friction resistance capacity by chemically coating the surface of yarn/fibres. Further, number of threads in warpers beam sheet is very less against number of threads required in whole width of fabric. Hence multiplication of sheets by drawing yarns together from many warp beams and again making one sheet is also performed on sizing machine. On sizing, normally, 8-

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12 % size material on warp thread is applied. This improvement in strength and frictional resistance characteristic of warp yarn is essential because during weaving, yarn has to undergo severe strain & stress as well as frictional operations

Indigo Rope Dyeing : Some Important Technical Considerations

September 13th, 2009 by Sandeep Agarwal | Filed under Denim - Developments.

Rope Dyeing is considered a superior dyeing technology where the dyeing uniformity achieved is better than other Indigo Dyeing technologies like Slasher Dyeing. However, Rope Dyeing is a also a more difficult dyeing technology. One needs to master its nitty gritties to get the best out of the system.

I , recently came across a very well written article on Rope Dyeing and thought it appropriate to share here.  The article mentions in great details the technical points to be kept in consideration while using Rope Dyeing..

Read on only if you are very technically oriented !

Notes on Yarn for Rope Dyeing

* Yarn faces stress and stretch at ball warping, rope dyeing, rebeaming, sizing and loom shed so elongation of yarn should be more than stretch at (ball warping + Robe Dyeing+ Rebeaming + Sizing )= (2-3%) + Loom shed (about 5%)

* Tension at Ball warping should be less by 7-8% of single yarn strength.

* Strength CV should be within limits as it may give rise to weak points

* The tendency of yarn to migrate at rope dyeing can be countered by less micronaire of yarn ( should be around 3.8-4.2)

* More dropping of short fibers at long chain beaming is good

*The sensitivity settings for neps is set at +280 for rotor spun yarn and not +200 as in case of ring spun yarn. The reason for this is that the structure of rotor spun yarn is intrinsically different from that of conventional ring spun yarn. Neps in rotor

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yarn tend to be spun into the solid yarn body rather than remaining on the yarn surface, which is typical of ring spun yarns. Although embedded in the yarn core, these neps still represent a short mass defect and will therefore trigger the imperfection counter upon exceeding the preset value. However, compared to neps that are attached to the yarn surface, fully embedded neps are barely perceptible for the human eye. Thus, in order to balance the typical visual appearance of rotor spun yarn with the imperfection counts, +280 sensitivity setting is a common convention for rotor spun yarns.

Comparison of Ring Yarn with OE yarn at Ne 7

1.

Process of dyeing of sulphur color in Indigo Dyeing Range:

1st Wash tank: mercerisation by taking 22% NaOH ie. 250 gpl 2nd Wash Tank: Hot Wash 3rd Wash Tank: Cold Wash 2. In 1st and 2nd dye bath take sulphur color 6-8% on the weight of the yarn sheet. Temperature 90 deg. cel. The solution contains the following: 1. solubalised sulphur color: 150 gpl 2. Na2S–> reducing agent: It is added to increase its reducing power 3. Caustinc Soda –> 10 gpl–> reducing agent 4. Wetting agent–> 2gpl 5. Antioxident Sulphide ( Glucose paste–> 5gpl). This is added to prevent the oxidation of of Sulphide solution. It will always remain in reduced form ( Alos if the shade is slightly greyish, one can add tiny tinge of sulpher blue–> 20gpl) in III, IV and V dye bath–> cold wash in 6th dye bath. We take H2O2(30%)+Acetic Acid(2:1 by weight). H2O2 acts as an oxidising agent. But as it acts on neutral pH (=7) and after cold bath the solution is slightly alkaline, to make it neutral wil add acetic acid. Acs in alkaline pH, oxidising action of H2O2 will be similar to the bleaching action, which may cause tendering in the fabric. 7th and 8th Dye Bath: Cold Wash

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Wash Box Number 4: Here washing is done with detergent and soda ash at 60-70 deg.c 5th and 6th Wash Box: Hot Wash 7th wash Box: Here softner is added at 25 gpl. It is cationic softener with pH 4.5 to 6.5. As during oxidation of sulphur, strength is reduced by 10%. On a yarn sulphur is of two types : 1. Free Sulphur 2. Reacted Sulphur. The free sulphur will react with moisture in the atmosphere to form: H2O + S –> H2SO4 Which tenders the yarn. Now at acidic pH reaction is much faster. So we add only a small amount of softener (25 gpl) as against that in indigo which is 100gpl. 3rd Point Over all during sulphur dyeing and storing, the yarn strength is reduced by 15% as compared to Indigo. 4th point If ball formation takes place of sulphur dyed warp at loom shed, then we can taken in 4th dye bath little Na2S+Caustic to reduce the free sulphur.

Technical Considerations in Rope Dyeing for Indigo dyed Denim.

The passage of yarn in rope dyeing is as follows: Pre-scouring –>hot wash–>cold wash –> Dye baths–> hot wash–>cold wash–> application of softener lets discuss these processes one by one: Pre-scouring 1. The objectives of pre-scouring are the removal of wax content from cotton, removal of trapped air from cotton yarn and Making yarn wet 2. This is done at 90 o C 3. We use the following ingredients at pre-scouring stage: Caustic Soda: Its quantity depends upon the quality of cotton fibres used in the mixing. Generally we take 2-4% of caustic soda. It removes the wax by the action of soapanification. Wetting agent: It is anionic in nature Sequestering Agent: Even with the use of water softening, it is very difficult to find the desired softness in water ( about 2-3 ppm) . So we use the agent to make the water soft. 4. Why Trapped Air should be removed. The reason for this can be understood as follows: In 1 kg of yarn, there is approximately 2 litres of air. 1 litre of air decomposes 1.8

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litres of Sodium Hydrosulphide. It will cause uneven dyeing and more consumption of Sodium Hydrosulphide ( hydro). 5. Absorbency of yarn may be checked after scouring. Hot wash As some caustic is carried by the yarn after pre-scouring, so hot water is given at 70-800C. If this is not done, this yarn will go into the dye-bath which will change the pH of the dye-bath. Cold Wash After hot wash, yarn temperature is more. To bring it back to its room temperature, cold wash is given to it. INDIGO DYEING

1. Indigo is not a perfect vat color. It may be called a trash vat color. The constant of substantivity for other colors is 30, for indigo it is only 2.7. So there is a need of 5 to 6 dye baths and make the use of multi-dip and multi-nip facility to increase the penetration. 2. The dyeing is done at room temperature as indigo belongs to Ik class of vat dyes, where dyeing is done at room temperature and oxidation is done by air only and not by chemicals. If oxidizing agents are used, they will cause stripping of colors. 3. Indigo is not soluble in water. So it is reduced with Sodium Hydrosulphide. Then caustic soda is added to make sodium salt of vat colors to make it soluble. To reduce 1 kg of Indigo, 700 gms of sodium hydrosulphide is required. However some extra SHS needs to be taken to avoid some decomposition of SHS. Practically it is prepared in the following sequence -Take indigo -Add caustic -Then reducing agent 4. When caustic is added to indigo, it is an exothermic reaction. It is allowed to cool down, then before sending it to feeder, sodium hydro-sulphide is added. Reducing agent is not added first as it will be decomposed first, so consumption of it will increase. It is also not advisable to take solubalised vat, as offered by some companies due to the following reasons: a. If it is used after 6 months, there will be a decomposition of sod. Hydrosulphide. It will become partially soluble. Then to make it soluble again, more SHS has to be added. b. Transportation is difficult c. Cost is more 5. Feeding System Rat of flow of yarn is given by

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((No of ropes x no of ends x speed of machine)/ count x 1.693 x 1000) in kg of yarn / minute So we can determine the rate of feed of indigo. It is very important that replenishment of indigo is there as any variation will result in the change of shade and also if level is more, there is a problem of over-flow. 6. If total capacity of dye bath for example is 15000 litres, then circulation must be 3 times the volume. If it is less then there are 100% chances of getting a lighter shade. 7. Core and ring dyeing effect This effect is obtained by multidip-multinip facility 8. pH of the Dye bath should be kept in between 10.5-11.5. At this pH , sodium salt of Indigo is mono phenolic form. At this form, the strike rate of dye is very high. So after washing, there will be a better dye effect. At pH 11.5 to 11.7, at this affinity is less, so dye effect will be less prominent. pH is controlled by the addition of caustic soda. 9. Testing of Hydro TOTAL HYDRO We take 10 ml of indio with SHS in 30-35 ml of water. It is set for one minute and shaken. As air will decompose SHS. So vacuum created will fetch the water from above. If 3 ml of water is required, then concentration of hydro is 3 gpl. As a thumb rule, concentration of total hydro should be min. 1.5 gpl. REDUCED HYDRO It is the hydro that is used for the reduction of Indigo. It should be around 0.7 ( 1000 kg of Indigo needs 700 kg of hydro to reduce it). For testing we take 10 ml of dye solution and 30 ml of water and 5-6 drops of 40% formaldehyde and shake it for one minute. The water that goes gives the readings of the reduced hydro. Total Hydro- Reduced Hydro = free hydro If Total hydro is min. 1.5 gm/lit. then free hydro must be min. 0.5 gms/ litre which acts as buffer 10. Also hydro reduction capacity is measured by mV meter which measures the Redox Potential. It should be around 760-800 Through the day, the redox potential should be +- 20 mV of the norm. If it is more then the process control is a failure. Caustic–> It is around 0.4 to 0.5 times the hydro used. Washing Rubbing fastness of indigo is very important. On a scale of (1-4), it is 2. Washing is done to improve the rubbing fastness. Wash at 60 deg.–> Wash at 60 deg.–> Wash at room temperature–> wash with softener

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Why Softener: 1. The rope is going to be opened at Long Chain Beamer. It the softener is not used, opening will be hampered. 2. It is generally 1.2% of the weight of the yarn. It is a cationic softener. It is always having pH in the range of 4 to 55. Softening is done at room temperature. If high temperature is used there is always some chance of tendering of yarn. 3. Concept of Buffer pH is given by Virkler USA, they say by addition of this, there is 40% less consumption of Indigo for same shade depth. 4. Metering Consumption If solution is of 900 litres 10% Indigo–>90 litres Hydro–> 90*.7 = 63 kg Caustic–> 63*0.445= 28 kg.

It belongs to a VAT class of dyes. It has a dark blue color wit a bronze lustre. It belongs to KI class of dyes. In this class, dyeing is done at cold and air oxidation is done to reoxidise the dye. It can be applied on both cellulosic and protein fibres. For protein fibres, a weaker alkaline solution is used. It can be reduced by NaOH and Na2SO4 in water to give monophenolate and biphenolate ions as complete solution. Reduced form of Indigo is called leuco indigo. Leuco has got low affinity for cellulosic fibres. Dye take up can be improved by: 1. Either mercerisation of cellulosic fibres before by dyeing 2. or by adopting multidip, squeeze and airing process, so that dye is coated on the fibre layer by layer Indigo can be further developed into Halogenated derivatives and sulphonated derivatives. Halogenated derivatives give better fastness properties and brighter shades, whereas sulphonated derivatives gives a soluble blue dye, good dye and is applicable on protein fibres. reaction : Image 1 Although indigo is a vat dye, it can be regarded as a ‘trash’ dye, the dyeing and fastness properties are in no way comparable to other class of vat dyes. It is due to these properties, that make it an excellent dye for denim. The on tone fading and the bleach down properties of indigo blue has generated a lot of denim jeans fashions like stone, ice faded looks, etc. These special effects cannot be simulated by the other classes of dyes. During Preparatiuon of stock vat, the following points must be remembered: 1. Vatting temperture should be as close to room temperature as possible. 2. Stirring should be minumum, unnecessary stirring affects the stability of reduced vat.

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3. Volume of the reduced vat should be kept constant for every stock vat batch, as the constant volume will ensure a constant replenishing amount. For rope dyeing system, with chemical replenishment with Stock replenishment Indigo: NaOH: Na2SO4 :: 1:0.8:0.8 Without stock replenishment indigo: NaOH: Na2SO4:: 1:1:1.2 Chemical Feeding NaOH: Na2SO4: : 1: 1.2-1.6 ie. for approximately 60 gpl of NaOH–> 120 gpl of hydro is required

Indigo Dyeing process control

1. Concentration of Hydrosulphite It is measured by vatometer. It should be from 1.5 gpl to 2.5gpl , or by redox potential of dye bath which should be from -730 mV to -860 mV. 2. Caustic Soda or pH value Should be from 11.5-12.5 3. Dye concentration in Dye bath it is measured by spectrophotometer. It should be in g/l Guidelines High Indigo Concentration –> Shade is greener and lighter Low Indigo Concentration –> Shade is dull and Red. High pH or Caustic Concentration –> Redder and lighter Low pH or caustic concentration –> greener and darker Dipping Time Longer the dipping time, better will be the penetration and lesser will be the ring dyeing effect. It varies from 15-22 seconds. Squeeze Pressure High pressure will lead to lower wet pick up and result in lesser color and better penetration. At rope dyeing, squeeze pressure is 5-10 tonnes, ie. wet pick up is as low as 60%. Hardness of squeeze roller is about 70-75 deg. shores. It sqeeze rolls are too hard then there are chances of slippage and uneven yarn tension.. If squeeze rollers are too soft then shading will occur. Surface of the squeeze rolls should be ground twice a year. Airing Time It should be 60-75 seconds. Longer airing time results in high tension on the yarn and subsequent processes will become difficult.

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Drying Insufficient or unevenly dried yarns will result in poor rebeaming Calculation of Replenishing Dye feed/min Conc. of stock vat is g/l= 90 range speed in yards/min=25 count = 7s totoal ends = 4100 Wt of yarn dyed /min= (4100*25*1000)/(7*840*202)= 7924 gms shade desired = 2% Amount of dye to be replenished/min= 158.5 gms Effect of pH At pH of 10.5 to 11.5, there will be formation of more monophenolate ions, which lead to higher color yield, as strike rate of the dye to the yarn bundle is very high, and wash down activities will be very good. At pH higher than this, dye penetration will be less and wash down characteristics are also poor. Testing 1. Alkalanity in Dye Bath Liquor Pipet 10.0 ml of vat liquor into 100ml of distilled water in a 150 ml beaker. place under continuous agitation and insert the electrodes of a pH meter caliberated at pH 7.0 with standard buffer solution. Titrate with tenth normal HCl ( 0.1 HCl) to pH 7.0 (ml = A) calculate g/l of NaOH = A *0.40 2. Hydro in Dye bath Liquor Add 2 ml of 37% HCHO to 150 ml beaker. Add 2 ml of dye range liquor . Add 6 ml of 25% glacial acetic acid solution prepared by diluting 1 part acid with 3 parts water. Add 2 ml of starch/KI indicator. Add ml of water. Titrate with 0.046 N ( prepared by diluting 460 ml of 0.1 N Iodine to one liter ) solution until the color changes from emarald green to bluish purple. G/l of hydro= mo fo 0.046N of Iodine Importance of High Concentration of Free Hydrosulphite The clearest shades with minimum reddish streaks are observed at by relatively high conc. of hydrosulphite. On the other side, with lack of hydrosulphite, the leuco indigo is less dissolved and thereby adheres to a greater extent to the fibres. With lack of hydrosulphite furthermore, the amount of unreduced dyestuff by oxidation at the upper level of the liquor

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and through activiation of unfixed dyestuff, gets separated from the fibrous material would constantly rise as the reducing agent for creating leucoform would be missing. Under these circumstances a reddish bronze like shade results due to dispersion of not reduced dyestuff in the yarn. The min. proportion of hydrosulphite should be around 1.3 to 1.5 gpl in case of rope dyeing and 3-4 gpl in case of sheet dyeing. Also to avoid the lack of hydrosulphite or Indigo at certain places in the immersion, vat, the whole quantity of the liquor should be circulated 2-3 times every hour. Reaction Time At very short reaction time, an adequate liquor exchange ( i.e. the amount of chemicals consumed and replaced by fresh addition of reduced indigo) is not assured. This has a negative influence on dyeing and depth of dye penetration. In addition to this the time available for diffusion of dyestuff until oxidation commences is too short. To ensure an even and good depth of dye penetration by dyeing in several passages, the reaction time should be 20-30 sec. for each vat (eg. at a speed of 20m/min for a reaciton time of 10 seconds, the immersion path should be maximum 3.3 meters). A reaction time exceeding 60 seconds should be avoided as the amount of dyestuff again get reduced and released may again supersede that of additionally take up dye stuff, resulting in higher shades. Softening Agent: 8 g/lit Drying: Rest humidity should be 30% and then sized. Addition of chemicals 1. Red Tinge: reduce addition of NaOH, increase slightly Na2S2O3 2. Darkish Red: increase Hydro 3. Light Greenish: decrease Hydro 4. Dark Green: Increase Caustic

Indigo dyeing calculations

For 12 ropes, at 24 m/min, of 344 ends of 14000 m length of 7s count. wt of yarn = (12*344*14000*100*453.6)/(7*840*36*2.54*1000) kg= 5000 kg at 24 m/min, a lot of 14000 m will be completed in 14000/24 = 583.3 min at 1.8% shade 100 kg of yarn needs–> 1.8 kg of Indigo 5000 kg of yarn needs –> 90 kg of dye at 100 gpl 100 gms of dye = 1 lit of solution

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90 kg of dye = 900 litres 900 litres should be completed in 583.3 min 1 litre would be completed in = 583.3/900= 38.8 seconds so flow rate will be 38.8 seconds / litre Similarly flow rate of caustic and hydro can be determined Hydro is taken around 100 gpl caustic is taken around 90 to 100 gpl

Indigo preparation sequence

In a tank of 1000 liters: a. take 400 litres of water (soft) b. add setamol ws–> 4 g/l (stirring) ( dispersing solution) c. Add 100 kg of Indigo ( at 1.8 % shade -see the indigo calculations- stirring) d. add caustic soda –> stirring ( for solubilising and pH) e. allow to cool it for 2/3 hours f. Add hydrosulphide ( As reducing agent) g. Make the solution to 1000 l by adding water. If pH is fluctuating, if it is > 11.7 then hydro is added (2-3 kg), if (<11.2) then caustic is added. For 100 kg of Indigo, Caustic Required= 90 kg Hydro Required= 80 kg

Difference Between Rope Dyeing and Sheet Dyeing

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THE A-Z OF DENIM

A complete A-Z glossary of denim terms from finishes, detail and weaves to mills, branding and history ...

Simply click on a letter below to skip

a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | y | z

a

ABRASION

Process of making garments look worn and aged by scraping or rubbing the surface of the fabric causing abrasion. Pumice stones are most frequently used by industrial laundries.

ACID WASH

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(Marble/ Moon Wash/ Snow Wash)- This finish gives indigo jeans sharp contrasts. The process is achieved by soaking pumice stones in chlorine and letting these stones create contrast. The process was created in Italy and patented in 1986.

AGED

A kind of wet processing that gives the garment an artificial worn look and a softer feel through prolonged abrasion.

ANTI-TWIST

A step in the finishing process, before sanforization, that corrects denim’s natural tendency to twist in the direction of the diagonal twill weave. Also known as skewing.

AMOSKEAG

A New Hampshire factory town which was the first major source of denim in the US. The Amoskeag Manufacturing Company opened in 1838 and by 1900 claimed to be the world’s biggest textile producer; it later declined due to industrial unrest and competition from southern mills. On Christmas Eve, 1935 the Amoskeag Manufacturing Company closed abruptly closed its doors and filed for bankruptcy and a flood soon after crushed any hope of reopening. Denim from Amoskeag was prolific and hugely influential in the success of the fabric, being used exclusively for Levi’s® 501 until 1915.

ARCUATE

Distinctive  double stitching used on the back pocket of the very first  Levi’s® jeans, now acknowledged as the world’s oldest clothing trademark. The shape became synonymous with Levi’s® jeans by 1900, although it’s conceivable that other early work wear might have used the device before them. LS&Co. trademarked the stitching in 1943.

ATARI

A Japanese term describing the selective fading of the ridges of creases. The most common areas for ‘Atari’ are along side seams, on the front and back of the knees, the upper thigh, along the hem, on belt loops and along pocket seams.

AUTHENTIC

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A jeanswear term used to describe both original jeans qualities and stone and enzyme wash optics. It became a marketing buzzword in the early 90’s, when the quest for original denim swept the European market. Among the characteristics of authentic jeans are traditional fabric weaves and styling details.

b

BACK CINCH

Also known as martingale, the back cinch with a back buckle was used to tighten the waist on jeans before widespread use of belts; hence the term ‘buckle back’. Most jeans makers abandoned them by 1942; with renewed interest in vintage-style looks, cinch backs have returned on modern jeans including Evisu, Atelier La Durance and Levi’s®.

BACK POCKET FLASHER

A paper or cardboard flap attached to the right back pocket of jeans and used to communicate differences in denims, washes, styles and size.

BARTACK

A sewing procedure that reinforces stress points on jeans- usually found near zippers and pocket openings.

BELL BOTTOMS

A jeans style born in the late ‘60s and popularized in the 70’s by brands such as Landlubber Jeans. This style was tight at the waist and thighs and the trousers flare out from the knee down. The name ‘bell bottoms’ presumably originates in the fact that the legs of these jeans take on the shape of a bell or trumpet when viewed from the side.

BELT LOOPS

Belt loops were first added to the waistband of the Levi’s 501 jean in 1922 to allow a belt to be worn without slipping. Both suspender buttons and the cinch back still remained on these first styles. A classic pair of jeans usually has 5 belt loops – 2 in front above the front pockets, 2 more at each side and one at the back.

BIG E

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A term used to describe Levi’s® clothing made before 1971, at which time the all uppercase logo on the red tab was redesigned with a lower case ‘e’. Levi’s® jeans with a big ‘E’ are considered vintage and more valuable than later little e’s.

BLACK-BLACK DENIIM

Denim where the warp yarn is black instead of blue and which is also dyed black after weaving. this makes the jeans truly black rather than gray.

BLEACH

A chemical used to make denim fade. Liquid bleach is usually an aqueous solution of sodium hypochlorite, and dry powdered bleaches contain chloride of lime (calcium hypochlorite).

BOOT LEG

A popular jeans style cut wide enough in the leg to accommodate a pair of cowboy boots underneath.

BROKEN TWILL

A denim weave first used by Wrangler in 1964 as style 13MWZ. The diagonal weave of the twill is intentionally reversed at every two warp ends to form a random design. This type of weave reduces the natural torque characteristic of regular twill weaves, and has the effect of eliminating leg twist.]

BUDDY LEE

This cherub-cheeked ceramic doll, clad in Lee overalls, was introduced in 1920 as H.D.Lee’s first promotion. As popularity grew, the doll gained a larger wardrobe including cowboy duds and railroad uniforms. Production stopped in 1962 and today the dolls are favourites with collectors.

BULL DENIM

A heavyweight denim weave (14oz. plus) with a typical 3x1 twill construction. An ecru fabric, bull denim is later printed or garment dyed.

BUTTON

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The traditional jeans button is made of two parts: a short ‘nail’ fixed on the fabric and the visible part pressed on the nail. It is typically made of a metal alloy- copper, brass or aluminium- and bears the brand’s logo, symbol or initial on its face. Some jeans buttons, composed of three parts, have a moveable head for better flexibility in fastening.

c

CASTE

A term that describes shading. Depending on the method and type of dye used, indigo denim can have a black, brown, gray, green, red, or yellow caste to it.

CELLULOSE ENZYME WASH

Enzymes which are like yeast , are used to physically eat away the cellulose in cotton. Since the colour in denim fabric is actually on the outside of the yard, when the denim is washed in a cellulose enzyme bath the indigo is removed along with the fiber. When the desired colour has been achieved, either changing the alkalinity of the bath or heating the water stops the enzymes from reacting. A rinsing and softening cycle follows. This process is more environmentally friendly than stone washing because strip-mined pumice stones are not used.

CHAIN STITCHING

A series of looped stitches that form a chain-like pattern. Chainstitching pulls the denim at slightly different tensions on either side, causing the distinctive ‘roping’ that really shows the beauty of worn indigo-dyed denim.

COIN POCKET

The fifth pocket, also called watch pocket. Strictly functional, it sits inside the right front pocket and justifies the term five-pocket jeans. Also known as match or

watch pocket.

CONE MILLS

Cone Mills started producing denim in 1895 in Greensboro, North Carolina. The company started supplying denim for Levi’s® jeans in 1910, becoming the exclusive supplier for the 501 in 1922. Cone is still one of the world’s biggest denim manufacturers.

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CROSSHATCH

A unique type of denim that shows a square grid-like pattern in the weave. It is created by mixing uneven yarns in both the weft and warp directions.

d

DENIM

A sturdy cotton twill fabric characterised by a 3x1 warp-faced weave in which the weft passes under two or more warp fibres producing the familiar diagonal ribbing, identifiable on the reverse of the reverse of the fabric. Traditionally denim is made with indigo-dyed yarn for the warp and natural yarn for the weft.

Originally called Serge De Nimes for the French city where it was produced, denim is now manufactured in specialized mills around the world.Denim is an indigo-dyed cotton twill fabric, woven  with a dyed warp yarn and a natural fill yarn. The term derives from Serge De Nimes; but denim and Serge De Nimes are in fact different fabrics.

DESIZING

An amylase enzyme rinse (desize) used to soften denim. A type of size such as cornstarch is added to the warp yarns prior to weaving in a process called slashing, which adds stiffness to the yarns. During the desizing step, the amylase enzyme attacks the starch and removes it from the fabric. Although this process reduces colour slightly, it is primarily used to give a softness and drapability to denim.

DIPS

Used to describe fabric or yarn when they are immersed in dye. Indigo yarns are usually dipped in an indigo bath six times.

DUAL RING-SPUN

Also called “ring X ring”. Signifies a denim weave in which both the warp and the weft threads are made of ring-spun yarn. Creates a much softer and textured hand than both open-end and regular (single) ring-spun denim. Due to the additional labour required to produce dual ring-spun denim, it is usually only used by higher end, premium denim labels.  

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e

ENZYMES

Enzymes, which are proteins present in all living cells, speed up chemical processes that would run very slowly if at all. They are non-toxic and readily broken down. Enzymes are used in textile processing, mainly in the finishing of fabrics and garments.

ENZYME WASH

Considered a more efficient and environmentally sound way to stone wash jeans. Rather than using pumice stones, organic enzymes (proteins) are used that eat away at the indigo. Jeans finished using enzymes tend to be stronger than those broken down by traditional stone washing, as the fabric is not subjected to the same level of abuse.

f

FINISHING

The techniques or processes performed on a garment, which give it it’s unique look.

FIVE POCKET JEANS

One of the most common styles of jeans; they have two back pockets, two front pockets and a coin pocket inside the right front pocket.

g

GARMENT DYE

A dyeing process performed on finished garments, as opposed to a yarn dye, which takes place prior to the weaving of yarn. If you see pocket linings or labels that look the same colour as the self-fabric, the garment was likely garment dyed.

h

HAND

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A description of the way a fabric feels. A subjective judgement of the feel or handle of a fabric used to help decide if a fabric is suitable for a specific end use. The hand can be described as crisp, soft, drapable, smooth, springy, stiff, cool, warm, rough, hard, limp, soapy etc. Finishing and garment wash will affect the final hand of a fabric.

HANK DYEING

This is a very special dyeing process that very few people use. The yarns are loosely arranged in skeins or hanks. These are then hung over a rung and immersed in a dye bath being dipped in and out and left to oxidize in the air between each dip giving the yarns a natural irregularity of patina and caste. In this method, the colour penetration is the best and the yarns retain a softer, loftier feel.

i

INDIGO

The dye used for denim, initially taken from the indigofera tinctoria plant. It was synthesized 14 years after it’s chemical structure was identified by Adolf Bayer in 1897. Indigo’s inherent features are good colour fastness to water and light, a continual fading and it’s inability to penetrate fibers completely. This allows the blue colour in jeans made dyed with indigo to always look irregular and individual. Pre-1920’s jeans were generally dyed with natural indigo and were- as far as one can tell by comparing vintage examples- paler in colour, with a green cast. Later jeans were a darker blue, particularly used in combination with sulphur dyes. The majority of indigo used today is synthetically made. Natural indigo has a slightly red cast.

IRO-OCHI

Japanese term referring to the fading of indigo dye in denim. The term specifically relates to fading in exposed areas and not across the entire garment.

j

JEAN

The term is possibly derived from the French word ‘genes’. It was originally used to describe the type of pants worn by sailors from Genoa. While the historical definition implied that all jeans were made of denim, the term jeans today can

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sometimes refer to a garment that has five pockets and be made from fabrics such as corduroy, twill or bull denim.

k

KHAKI

Chinos, combat pants, military styles in khaki and olive- these became a popular replacement for jeans amongst the youth of the 90’s.

l

LAUNDRY

In the ‘Denim Industry’, a Laundry is a manufacturing company that takes unwashed jeans and processes them. This processing includes washing, stone washing, sandblasting, garment dyeing , finishing, use of ‘Tonello’ machine with abrasive bristles, applying enzymes to simulate a ‘whisker’ effect and sandpapering by hand. Laundries today are critical in making jeans look commercial and wash development has become as important as fabric development in the denim industry. The best Laundries and wash developments come from the U.S, Japan and Italy.

LEFT-HAND TWILL

Also known as an ‘S Twill’, this is a weave in which the grain lines run from the top left-hand corner of the fabric towards the bottom right. Usually in piece dyed fabrics, left hand twill fabrics are woven from single plied yarns in the warp. The denim brand Lee has always used left-hand twill denim as it’s basic denim. Left-hand twills will often have a softer hand feel to them after washing than right hand twills.

LEG TWIST

Many vintage jeans suffer from leg-twist. This is simply a natural adjustment of the fabric, which tends to follow the direction of the weave. Stefano Aldighieri, Director of Fabric & Finishing at LS&Co. explains it thus: “Levi’s® denim were mostly right hand twills; the twill line rises to the right. During the weaving process you basically ‘force’ the fabric to be straight, perpendicular to the selvage, but at the same time you give it this direction in the construction. You lay and cut the fabric; in the early days LS&Co. patterns were cut straight along the selvage.

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When you wash the garments, the fabric will try to follow the direction of the weave and will pull in that direction... hence the twisted legs, the result of the movement of fabric. Because Lee started to use left hand weave denims, their legs would twist the other way.” Leg twist was eliminated in the 1970s by skewing (which contorts denim to its after-wash shape)- and later revived with Levi’s® Red and Engineered jeans.

LOOP DYED

One of the three major industrial methods of dyeing indigo yarns. In the loop dyeing process, the yarn is dyed in a single bath instead of several. The desired depth of colour is attained by passing the yarn through the vat several times. Subsequently as part of the same process, the yarn is sized.

m

MERCERIZATION

An industrial process used on yarn or fabrics to increase it’s lustre and dye affinity. For fabrics used in the denim industry, mercerization can be used for keeping dye on the surface of the yarns or fabrics and to prevent dyes from fully penetrating the fibres.

MICROSANDING

In this fabric treatment process, a series of cylindrical rolls in a horizontal arrangement, either wrapped with an abrasive paper or chemically coated with an abrasive , are used to create a soft, sueded hand. The denim is pulled over the face of the sand rollers creating a raised surface finishinig. Some colour reduction is experienced.

n

NATURAL DYE

Up to to the middle of the 19th century there were only natural dyes and most of these these were vegetable origin. Natural indigo being one of the more important dyes. Natural dyes usually have no affinity for textile fibres until the fibres are treated with aluminum, iron, or tin compounds to receive the dye (mordanting). This is a problematic process and the dyes in any case have poor fastness to sun or abrasion.

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NATURAL FIBRES

Any hairlike raw material directly obtainable from an vegetable, animal, or mineral source that can be converted, after spinning, into yarns and then into woven cloth.

o

OPEN END DENIM

Open End or OE spinning was introduced in the 1970s, reducing costs by omitting several elements of the traditional spinning process. The cotton fibres are ‘mock twisted’ by blowing them together. Open End denim is bulkier, coarser and darker, because it absorbs more dye, and wears less well than Ring Spun denim. Although cheaper to produce it has been used on many designer jeans, including Calvin Klein and Tommy Hilfiger.

OVERDYE

A fabric dyeing process in which additional colour is applied to the fabric or garment to create a different shade or cast. ‘Dirty Denim’ is often created by applying a yellow overdye to denim. By localising the application of the tint, you can create specific areas that look dirtier than the surrounding areas.

OXIDATION

Occurs when oxygen and another substance chemically join. This occurs when indigo yarn comes out of the bath between dips.

p

PIGMENT DYES

Dyes that do not have an affinity for fibre and must therefore be held to the fabric with resins. They are available in almost any colour and are used extensively in the denim industry by fabric dyers who want to create fabrics that fade more easily.

PLY

All yarns are single ply unless twisted with another yarn. Plied yarns are used to make yarns stronger. In the denim industry, it has become important to ply yarns stronger. In the denim industry, it has become important to ply yarns in piece dyed

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fabrics that are intended to endure a long stone wash cycle. The method of twisting and length of each yarn is a major determinant in the ultimate look and feel of the finished fabric.

POLYCORE DENIM

Often found in replica jeans, offers the best mix of strength (polyester core) and vintage aesthetic (cotton top thread layer).

PUMICE STONES

Volcanic stone used for stone washing garments. Pumice is popular because of it’s strength and light weight. Before the use of pumice, rocks, plastic, shoes and just about every other material was used to wear down and soften denim during the laundry process.

q

QUALITY CONTROL

Each pair oj jeans is subjected to a series of quality checks. The first random samples are examined during pre-sewing. Then after the pieces are assembled, every single pair of jeans is individually examined, and again after washing.

r

RIGHT-HAND TWILL

Most denim is right-hand twill, a weave which produces a diagonal, or twill, line which rises from left to right. This was standard practice in weaving; single yarn warps were woven right-hand, double yarn warps were woven left hand. Most Levi’s® jeans are right-hand twill whereas most Lee jeans are left-hand twill.

RING DYEING

Describes a characteristic unique to indigo dye in which only the outer ring of the fibres in the yarn is dyed while the inner core remains white.

RING-SPUN DENIM

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Ring spun yarns were traditionally used in denim up until the late 1970s, but were later supplanted by cheaper Open End yarns. This is a spinning process in which the individual fibers are fed onto the end of the yarn while it is in the ‘twisting’ stage. The process consists of a ring, a ring traveller and a bobbin that rotates at high speed. The ring-spun yarn produced by this method creates unique surface characteristics in the fabric, including unevenness, which gives jeans an irregular authentic vintage look. Ring-spun yarns add strength, softness and character to denim fabric.

RING-RING DENIM

Ring/Ring, or double ring-spun denim uses ring-spun yarn for both warp and weft. This is the traditional way to produce denim. It’s possible to combine a ring-spun warp fabric with an Open End weft, to get much of the strength and look of the traditional ring/ring denim at lower cost.

RIVER WASHING

A washing process using a combination of pumice stones and cellulose enzymes to give denim a vintage, worn hand. The washer is loaded only with stones and fabric for the first cycle. Enzymes are introduced for the second stage in combination with the stones and they are tumbled until a naturally aged look is produced.

RIVET

A metal accessory that is used for reinforcement of stress points as well as for non-functional ornamentation.

ROPE DYEING

Considered the best possible method to dye indigo yarns. The threads of denim yarn are twisted into a rope, which is then fed through sequence of being dipped into a bath of indigo dye, followed by exposure to air, multiple times. The frequency determines the ultimate shade of blue.

s

SANDBLASTING

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A laundry process performed before washing in which jeans are shot with guns of sand in order to abrade them and cause a worn appearance. While originally done by hand this process is now automated at most large laundry houses.

SANDING/EMERSING

A fabric finishing process where fabrics are sanded with real sandpaper to make the surface soft without hair. It can be performed before or after dying.

SANFORIZATION

A pre-shrinking fabric process that limits residual fabric shrinkage to under 1%. The process includes the stretching and manipulation of the denim cloth before it is washed. Raw, un-sanforized jeans will shrink 7-10% after the first wash, and continue to shrink slightly up to the third wash. Developed in the late 1920s by the Sanforize Co. and patented in 1928, the process was reportedly first used by Erwin Mills in 1936 to make denim for overalls marketed under JC Penney’s Big Mac label. Lee jeans were made from Sanforized fabric soon afterwards, Lady Levi’s® introduced around 1935 were also Sanforized although most other Levi’s® jeans remained shrink-to-fit for another three decades.

SELVAGE

Also referred to as ‘Redline’ or ‘Aka-Mimi’. Originally called ‘self-edge’, the selvage is the narrow tightly woven band on either edge of the denim fabric, parallel to the warp. A selvage end prevents the edge of the denim from unravelling. Old 28 to 30 inch shuttle looms produce denim where selvages are closed, whereas on larger modern weaving machines, the weft yarn is cut on every pick, creating what is called a ‘fringe’ selvage. Coloured thread was used by Cone Mills to identify the particular fabric used by it’s major manufacturers. Vintage Levi’s® jeans began with an all white strip and later had a single red strip along both selvages, Lee’s had a blue or green strip along one end and Wrangler’s was yellow.

SHADE BATCHING

The process of selecting batches of fabric into homogeneous shade lots to obtain consistent colour continuity in garment making.

SHADE BLANKET

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Fabric is cut from each roll of fabric and sewn together with roll numbers on the back of each roll. This is an important tool in cutting apparel made from denim to ensure that garments from the same shade group are cut.

SHRINKAGE

Traditionally before denim is woven, the threads it’s made of are treated with wax or resin to stiffen them and make them easier to weave (although with most repro denim starch is used instead.) When dry/raw/unwashed denim  is washed for the first time the fibres constrict and the denim shrinks. Raw denim can be sanforized (treated with a sanforizing process that lessens shrinkage) but all raw denim will shrink to some degree upon immersion in water, up until it’s third wash.

SHED

During the weaving process, this is the opening formed by raising and lowering the warp yarns on a loom. The shed opening is what the weft yarns are passed through to complete the weaving interlace.

SHUTTLE

The device that carries the weft yarn across the loom in vintage shuttle looms. Selvage denim can only be woven using a shuttle loom.

SILHOUETTE

Refers to the shape of a garment (i’e bootleg, relaxed, low rise, slim, carpenter, etc...)

SIZING

Starch, gelatine glue or wax that is added to fabrics in the finishing stage to improve touch or weight and to help fabric laying in the cutting phase. Denim fabrics, for example can have almost one ounce of sizing.

SKEWING

Refers to the occurrence of twisting that happens when the fabric shrinks more perpendicular to the twill line than along the twill line. Without compensating for this occurrence, the twill line will cause the right angles that the fabric is woven in to torque approximately 5° after washing. To compensate for this, denim is skewed

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about 5° in the same direction as the twill line tom prevent the side seam from twisting to the front of the jean. You will often find authentic vintage jeans with one or both of the side seams twisted towards the front of the jean.

SLASHER DYEING

One of three main methods of dyeing indigo yarn.

SLIVER

In the yarn manufacturing process, a sliver refers to the loose, soft, untwisted rope of cotton fibers that is produced using the carding machine.

SLUB

Refers to thick or heavy places in the yarn. Slubs and other inconsistencies are common in denim produced on vintage shuttle looms. Modern yarn spinning technology is able to engineer these vintage looking textures into yarn in a predefined manner.

STONEWASHING

A process that physically removes colour and adds contrast. A 20 yard roll of fabric, generally 62 inches in width, is put into a 250-pound washing machine along with pumice stones. The fabric and stones are rotated together for a set period of time. The washing time dictates the final colour of the fabric- the longer the denim and stones are rotated the lighter the colour becomes and more contrast is achieved. The denim is then rinsed, softened and tumble dried. Both Marithe & Francois Girbau from France  and the Japanese ‘Edwin’ claim to have pioneered this finishing technique.

SULPHER BOTTOM

Many manufacturers apply a sulphur dye before the customary indigo dye; this is known as Sulpher Bottom dyeing. This can be used to create a grey or yellow ‘vintage’ cast.

SUSPENDER BUTTONS

Attached to the waist bands of jeans to attach suspenders and braces these became less common from the late 30s when suspender buttons were removed to make

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getting dressed easier for the modern belt-wearing man. However many retailers stocked and fitted ‘Press On’ buttons for customers who preferred suspenders to a belt.

t

TATE-OCHI

Japanese term referring to occurrences of ‘Iro-ochi’ forming in vertical lines in vintage denim. As the thread width is not uniform in vintage denim, the colour fades the most where the thread is the thickest. This creates a white or severely faded thread of several centimetres along a single vertical indigo thread.

TOP STITCH

A commonly used straight simple stitch.

TWILL

The diagonal lines formed by the weave.

u

UNWASHED

Exactly what the word says- jeans that have been left unwashed, a characteristic that goes back to pre-sanforized days, when manufacturers sold their garments dark, stiff and not pre-shrunk. Some brands offer jeans this way for purists who want to break in their own jeans on their own bodies to recapture the original magic of denim’s good old days.

USED WASH

Term referring  to a type of placed abrasive effect or sandblasting, made individually on each garment in special areas like the knees, pockets, thighs bottom etc...

v

VENETO

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A Northern Italian region considered the cradle for some of the most successful names of the International jeans industry. Denim brands such as Diesel, Replay, Gas and Seal Kay were all born and raised here as were famous laundries such as Martelli. 

VINTAGE

From the past; old or secondhand. Vintage jeans can either be previously worn or never worn and sorted in their original state

w

WAIST OVERALLS

The original term for what we know as jeans- Levi’s® continued to use this term up until the 1960s to distinguish their jeans from bib overalls.

WARP

This is the lengthways vertical yarns woven into the weft yarn. They usually have more twist and are stronger than weft yarns. In denim it runs parallel to the selvage and is dyed indigo.

WEAVE

The combination of warp and weft yarns woven into the weft yarns to produce different weave designs. The warp face designs used in the denim are called out by the number of weft yarns that the warp ends pass over followed by the number of weft yarns they pass under. Some of the most common denim weaves are 3x1 and 2x1 can be made in left or right-hand twill directions. 3x1 right-hand twill is the most common design.

WEFT

The un-dyed, crosswise filling yarns used in denim weave.

WEIGHT

Denim is traditionally graded by its weight per yard of fabric at a 29-inch width. Early Levi’s® were 9oz denim, increasing to 10oz in 1927; Lee 101 Cowboy Pants

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were introduced in the much heavier 13oz weight; most modern jeans are around 14oz.

WHISKERING

A fading of the ridges increases in the crotch area and back of the knees, which gives the appearance of aged denim. It can also be inverse- dark creased in faded denim.

x

XX

The name used originally to reference a particular model of Levi’s® jeans built prior to 1890. The XX has been present ever since and is used as both a lot or ordering number and to signify Levi’s® highest quality denim, ‘501 XX’, woven by Cone Denim.

y

YARN DYE

Refers to fabric in which the individual yarns are dyed prior to weaving- denim is a yarn dyed fabric.

YOKE

V-shaped section at the back of jeans, also known as a ‘riser’, which gives curve to the seat. The deeper the V of the yoke, the greater the curve. Cowboy jeans often feature a deep yoke whereas workwear or dungaree jeans might have a shallower yoke- or no yoke at all.

z

ZIP

The alternative to the button fly, first used for jeans by H.D. Lee in 1926. Wrangler was the first to do a centre zip fly for women in its Jeanie line, which debuted in 1950. The innovation was considered hazardous at first, but eventually became a huge success.

ZIPPER

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A popular jeans closure. Also sometimes used as a design detail on back pockets or on tapered pants legs. The zipper was invented in 1893 by American W. Litcomb Judson as a system of small hooks and eyelets; it was improved by Swedish Gideon Sundback in 1913, when it became a system of small metallic teeth intertwined with a movable clasp.