dyeing with indigo

8/3/2019 Dyeing With Indigo

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Dyeing with Indigo - Natural Fermentation Vat

Why Indigo?

Indigo is a dye different than any other. It does not

require any mordant. Rather it is dyed through a livingfermentation process. The process "reduces" the

Indigo, changing it from blue to yellow. In this state, it

dissolves in an alkaline solution. The fibre is worked in

the solution, or "vat". When brought out to the air, it is

a bright green. Slowly the air changes it to the

beautiful deep and rich blue of Indigo.

Indigo in some form is used in all traditional cultures, for it is the only clear and

fast natural blue. Indigo dyeing was one of the first speciality professions. Yet it

is easy to keep a home pot going, and most colonial homesteads had one. This

recipe is the one most commonly used for home dyeing. It contains no harsh

chemicals nor toxic metals. It can be used to dye any natural fibre.

An additional beauty of dark Indigo is that when ironed or pounded, the blue

cloth takes on a beautiful coppery sheen - the same sheen that is seen on the

well reduced Indigo vat, when it is ready for dyeing.

Indigo: Natural Vermentation Vat

NOTE: requires advance preparation of about one week.

4 oz. groundIndigo

2 oz. groundMadder 2 oz. wheat bran (buy at any health food store)

12 oz.washing soda("soda ash")

(above amounts are by weight ounces, not volume ounces.)

Combine in about a three gallon pot of warm water.

Always add these amounts in proportion. A larger vat can be made, for example

with: 1 lb. ground indigo, 1/2 lb ground madder, 1/2 lb ground bran and 3 lbs

washing soda in about a 10 gallon plastic tub. However, I advise starting small,

till you are comfortable with the process. The size of the pot is determined by the

amount of fobre you need to dye at one time. A three gallon pot is good for yarn

skeins of 4 to 6 oz., while a 10 gallon or larger tub will be needed for yards offabric.

WARMTH: It is necessary to keep the vat warm, but not hot, around 100 - 110

Fahrenheit. It is the same temperature for raising bread or making yogurt. It

should feel pleasantly warm to the hand.

click to enlarge

Buy Indigo

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To keep it warm, a light bulb in a reflector can be put under the vat, with a

blanket over it to keep in the heat. (See illustration, next page.) In a warm

climate no additional heat is needed, but be sure the vat is out of direct sun so it

does not overheat.

TIME is very important. It takes time for the vat to ferment and it does no good

to try to rush the process. The first time, it takes about a week for the vat to

ferment and be ready to dye. With "renewals" the time needed is a bit less, four

or five days.

It takes time to do the dyeing. The fibre is "dipped" several times to build up a

dark color, with airing between each dip.

The vat itself lasts a long time. I have had my current vat over fifteen years. In

traditional cultures there are vats over 100 years old. The vat is "renewed" with

more Indigo and the other ingredients in proportion, whenever the dye value

weakens. Then let sit a few days to re-ferment. Indigo dyeing by this naturalfermentation method is a slow-steady process. It is good meditation.

Stir the vat once a day. The idea is to integrate the undissolved Indigo, madder

and bran that settles to the bottom, back into solution. And to do this without

incorporating air into the vat. So stir gently.

Keep the vat covered. Air is the enemy of a good Indigo vat. The level of

liquid in the pot should just allow room for the yarn dyeing, without spilling. The

less air between surface and lid the better. I use a domed lid, turned upside

down. If you leave more than 2" of air at the top of the vat, it will not reduce

properly.

The vat is ready for dyeing when:

It develops a coppery film on the top of the vat.

The liquid, lifted carefully in a glass jar, will appear green.

A test piece of fibre or paper will emerge green and turn blue in the air.

Now is the exciting time to begin Indigo dyeing!

1. Wet your fibre out very well in warm water. It must be well wet out. Any

air remaining in the fibre will oxidize Indigo in the vat, and this must be

avoided.

2. Put on rubber gloves! You don't want to scare people with blue hands;

also the strongly alkaline vat may irritate your skin.

3. Enter the fibre (yarn/fabric) into the vat very carefully, to avoid adding

any air to the vat. Now the fibre must be "worked" in the vat, under the

surface. It should not be stirred, but with your gloved hands, gently,

slowly and deliberately squeeze the liquid through the fibre while you

hold it under the surface. Any time you break the surface you introduce


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air into the vat and this you do not want to do.

4. After you have worked it several minutes, carefully and slowly raise it out

of the vat, squeezing the excess Indigo solution back into the vat. Do this

squeezing as close to the surface as you can, as dropping liquid will bring

air into the vat.

5. The fibre should be a bright clear green. It will start to turn blue in the

air immediately. Lay it out on newspaper and let it air for 20 minutes.

Repeat the dips up to five times for dark Indigo Blue. Air between each

dip. For lighter shades, fewer dips are needed.

6. Rinse well. Then leave the fibre to air overnight. Soak and do a final rinse

in the morning.

The vat lasts indefinitely. It is begun with a certain amount of Indigo, and all

other ingredients as given, in proportion. Dyeing is begun, with the darkest color

dyed first, then medium, then lights. Between dyeings the vat must rest

overnight or an extra day. This is because, during dyeing a certain amount of the

Indigo is oxidized in the vat. Allowing it to rest lets it re-reduce that Indigo. An

oxidized (blue colored) vat won't dye well. The Indigo color will only wash out

and rub off too quickly.

When the vat is "exhausted", and will only dye light shades, it is time to renew it.

All ingredients are again added, again in correct proportion. The vat is let to

ferment for several days, and is ready to dye when it shows the proper signs. In

this way a vat can be kept going for many years.

If one wishes to rest from dyeing for several weeks, simply turn off the heat

source, and keep the vat cool for that period. Stir it vigorously on occasion.

When ready to dye again, warm it up, renew it with the ingredients, and proceed

as before.

It is not good to leave a vat unused for too long, as it is a living process and may

then get cranky about starting up again. Also it is important to exhaust the vat

before leaving it, or it may over-ferment and ruin any Indigo remaining in it.

Over time a deposit of sludge will develop at the bottom of the vat. You may

want to gently lower a screen into the vat before dyeing, to keep your fibre from

pickinging itup during the dye process. Be sure to remove the screen after the

day's dyeing, so you can stir the vat before closing it.

For greens, dye you fibre Indigo first, then rinse well and overdye with alum

mordant and your chosen yellow dye. For purples, dye the Indigo first, rinse well,then mordant and dye over with any red dye.

The indigo vat is very alkaline. It is important to rinse out all the alkalinity. Just

to be on the safe side, I always double rinse my indigo dyed textiles. First I rinse

well just after dyeing, then I let air overnight. Next day I soak in two successive

waters for about an hour each time, rinse again, wring and dry.


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Squeeze solution through yarn for best penetration. Always work under

the surface of the vat. Always wear rubber gloves.

More About Indigo

Indigofera is a legume. The plant looks similar to alfalfa, but is usually larger. It

is an excellent rotational crop for increasing soil fertility. In southern Mexico,

where some of the current Indigo of commerce originates, it is naturalized and

grows in fallow fields, so no effort is spent cultivating it.

Indigo dye must be prepared from the fresh plant in an exacting and elaborate

process that takes about a month. The Indigo plants are harvested and brought

to a central location. They are soaked in water and allowed to ferment. This

separates the dyestuff from the plant. The solution is then beaten to oxidize and

precipitate the Indigo. Excess water is poured off and the sludge is dried. This

sludge, packed into balls or patties and fully dried, is the Indigo dye of

commerce.

This Indigo comes to us in the form of a hard, dark blue colored cake. It must be

ground to be used for dyeing. Very small amounts can be ground in a mortar and

pestle. Use a bit of water to facilitate grinding and keep down the dust. A Corona

Corn mill is what I use. Meat grinders also work. A zip-loc baggie cinched over

the grinding plates catches all the powder and keeps blue dust from getting

everywhere.

In most traditional cultures, the color(s) of ones clothing indicates ones status or

class. Indigo blue has long been associated with the less than aristocratic

classes. Indigo blue has still the association of "The Working Class". We use the

distinction as "Blue Collar Workers" and "Blue Jeans". These clothes wereoriginally dyed with indigo. In the past, Indigo has been a prolific dyestuff. It is

relatively easy to grow and dye, and is quite fast. It withstands well the many

washings that work clothes require.

In most cultures, Indigo dyeing is or was a specialty. The dye process is unique,

and the facilities require a stable set-up. Vats made of great clay pots set in the

ground are commonly used in warmer climates. If more heat is needed, pits for

burning charcoal are placed between clusters of the vats.

Indigo dyeing is practiced today in Japan, Southern China, Tibet, India,

Indonesia, Indo China, Africa, especially Nigeria, Southern Mexico and

Guatemala, and it has recently been reintroduced to Turkey. Traditional

fermentation methods are used. However, many of these cultures now use

synthetic Indigo, manufactured from coal tar or petroleum.

Natural Indigo contains several related dye chemicals that give different shades

of blue. As much as twenty percent of the dye may be a violet tone called Indigo

Red. These complexities give Natural Indigo nuances and depths that cannot be


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achieved with the synthetic substitute. Here is a page with more about the

chemical properties of indigo.

An additional beauty of dark Indigo Blue, is that when ironed or pounded, cloth

so dyed takes a coppery sheen - the same sheen we see on the top of the well

reduced Indigo vat.

PO Box 14 Somerset, MA 02726 orders 1-800-2-BUY-DYE

technical support 508-676-3838fax 508-676-3980

e-mail [email protected]

Indigo

Please read the directions carefully before starting.

Indigo belongs to a class of dyes called vat dyes, which are among the oldest naturalcoloring substances used for textiles. Until the beginning of this century, indigo could beobtained only from plants. Two things are required to make indigo work, Thiox, thereducing agent, and Lye, the alkali. The dye vat is prepared in two steps: The stocksolution and the dye vat. The stock solution then added to the dye vat. Always do testsamples before working on a large project.

While Indigo and the chemicals used are comparatively safe and non-toxic, it is best to treat them all withcaution. Wear rubber gloves to minimize contact with hands. Eye protection is urged as you are working

with alkalies and strong reducing agents. Always work in a well ventilated area. Good house-keeping isessential to good results. Utensils used for dyeing should never be used for food preparation. See cautionfor Lye (Sodium Hydroxide) below.

Supplies:

For Cotton, linen, rayon, and silk For Wool

PRO Indigo grains PRO Indigo grains
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Lye (Sodium Hydroxide) Lye (Sodium Hydroxide)

Thiox (Thiourea Dioxide) Thiox (Thiourea Dioxide)

Metaphos Synthrapol SP

Non-Iodized Salt Unflavored Gelatin

Distilled White Vinegar Clear Household Ammonia

Ivory Bar Soap or Ivory Flakes Distilled White Vinegar

Ivory Bar Soap or Ivory Flakes

Procedure for dyeing cotton, linen, rayon and silk

1. Determine whether you wish to make a 20 gallon (80 liter) full size vat or 4 gallon (16liter) mini vat and prepare the stock solution.

Full size vat Mini vat

PRO Indigo 1 cup (70 gm) 3 Tbl (15 gm)

Cold water 6 cups (1.5 liters) 1 cups (375 ml)

Lye 1 cup (215 gm) 5 tsp (23 gm)

Thiox 2 Tbl (25 gm) 1 tsp (4 gm)

2. Mix Indigo with enough luke warm water to make a lump free paste.

3. Measure the COLD water into a separate container. Carefully add the lye and setaside to cool.

4. In a third container, add the Thiox to 1 cup (250 ml) of warm water (Mini Vat use cup (125 ml) water). Stir gently to dissolve.

5. Slowly add the lye solution to the pasted Indigo and stir to make a smooth mixture.

6. Next, slowly add the thiox solution. Avoid creating air bubbles.

7. Stir this mixture gently from time to time, until reduction is complete. Reduction iscomplete when the stock solution turns yellow. Otherwise the surface is a deep bluefrom oxygen coming in contact with the dye. Set the jar of stock solution in a pan ofHOT Water, if necessary. Raise the temperature no higher than 135oF (57oC) for 15 to30 minutes or until reduction takes place.


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8. Make the dye vat.

Full Size Vat Mini Vat

Warm Water 120oF(49oC) 20 gallons (80 liters) 3 gallons (12 liters)

Metaphos 3 Tbl (63 gm) 1 tsp (7 gm)

Salt 2 cups (600 gm) 1/4 cup (75 gm)

Thiox 4 tsp (15 gm) tsp (2 gm)

9. Measure warm water into dye vat container.

10. Stir in the Metaphos and salt.

11. Dissolve the Thiox in a small amount of warm water and add it to the dye vat.

12. Add reduced stock solution by carefully lowering the container into the Dye Vat andsliding the liquid out at an angle. Stir gently.

13. After 30 to 60 minutes the vat should be clear greenish-yellow with a shiny, darkblue metallic surface. The vat is then ready to use. If the vat is not clear and greenish-yellow in color wait an additional 30 to 60 minutes. It can take as long as 6 hours forproper reduction.

Maintaining the Indigo vat

* Every precaution MUST be taken to keep oxygen out of an Indigo vat!!!

* For your vat, use a deep vessel with a narrow top to minimize exposure to air.

* When adding additional Stock Solution or dissolved chemicals to the vat, do not pourthem in. Lower the container into the vat and slide the liquid out at an angle.

Using the Indigo vat

*Before dyeing, machine wash the fabric on HOT cycle with a minimum temperature of140oF (60oC) water OR by hand in a pot on the stove with tsp (2 gm) PRO DyeActivator or Soda Ash and tsp (2.5 ml) Synthrapol per pound (454 gm) of fabric.Rinse thoroughly.


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* Thoroughly wet fabrics before dipping in vat. A warm water soak for 15 to 30 minutesis recommended. Wearing gloves, squeeze out excess water evenly.

* Gently push the dark blue scum aside before entering fabric in the vat. Where scumclings to the cloth it will look dark blue. However, after dyeing is finished the spot will

wash off the surface, leaving a light undyed spot.

* Lower fabric into the vat very gently, without splashing.

* Slowly manipulate the cloth while working below the surface of the vat. This helps thedye penetrate. Keep fabric submerged for the duration of each dip, 2 to 3 minutes. DONOT SWISH the fabric around in the vat.

* Gently squeeze out excess dye BELOW the surface and remove fabric from the dyevat. DO NOT allow fabric to drip into the vat after dyeing.

*Let fabric oxidize (turn blue) for approximately 15 minutes. Repeat dipping andoxidizing until youve reached the desired depth of blue. If youve gotten some of thedark blue scum on your fabric, then give it a rinse in plain room temperature water. Thisway the fabric that is underneath the scum can oxidize. Let the fabric air dry beforewashing. Remember that after washing, the final color will be one to two shades lighter.If youve done a bound resist dyed fabric its best to let the fabric dry completely beforeuntying so the threads wont rip the fabric.

Washing the fabric

Wash the fabric in hot 135oF to140oF (57oC to 60oC) water for 10 minutes in a generous

bath of Ivory bar soap or Ivory Flakes. With a knife, its easy to flake off a 1/8 inch thickpeel of soap. Stir the wash bath occasionally and rinse the fabric until the water runsclear. Hang cotton and rayon to dry.

If youre dyeing silk then soak it for 10 minutes in a bucket of acid soak. Make the acidsoak by mixing 2 Tbl (30 ml) of White Distilled Vinegar in 1 gallon (4 liters) of roomtemperature water. Then rinse the silk thoroughly in plain water.

Troubleshooting the dye vat

* If the vat appears grayish and watery, it is exhausted. This means that all the indigo

has been used. An addition of Stock Solution is needed.

* If the vat has been left for a few days, it may need to be "Sharpened" with a smallamount ( tsp (2 gm) for full size vat) Thiox, dissolved in water.

* If the vat changes from yellow-green to blue, or if blue specks appear, more Thiox isneeded. Add a small amount ( tsp (2 gm) for full size vat) Thiox, dissolved in water.Stir gently. Wait 15 minutes and check vat again before dyeing.


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* If white specks appear or the vat appears "milky" add small amount (1 tsp for full sizevat) of Lye, dissolved in cup water. Stir gently. Wait 15 minutes and check vat againbefore dyeing.

* Occasionally, more than one addition is required to revive a vat. Use small amounts,

and wait 15 to 20 minutes between additions, testing each time. Excess alkali orreducing agent can unbalance the vat, making it impossible to build up deep shades. Bepatient, and the vat will have a long life.

* Always dissolve Thiox and Lye in water BEFORE adding to the dye vat. DO NOT adddry flakes.

* Cover with a tight fitting lid when not in use.

Troubleshooting fabric

* Dye washes off of fabric: too little reducing agent.

* Crocking off (Dye rubs off): too little alkali

Procedure for dyeing wool

1. Prepare the stock solution.

Mini Vat

PRO Indigo 3 Tbl (15 gm)

Lye 5 tsp (23 gm)

Thiox 1 tsp (4 gm)

2. Mix Indigo with enough luke warm water to make a lump free paste.

3. Measure 1 cups (375 ml) of COLD water into a separate container. Carefully addthe lye and set mixture aside to cool.

4.In a third container add the Thiox to cup (60 ml) water. Stir gently until its

dissolved.

5. Slowly add the Lye solution to the pasted Indigo and stir to make a smooth mixture.

6. Add the Thiox solution slowly to avoid making air bubbles.

7. Stir gently from time to time until reduction is complete. Reduction is complete whenthe stock solution turns yellow. If necessary set the jar of stock solution in a pan of HOT


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Water. Raise the temperature no higher than 135oF (57o) for 15 to 30 minutes or untilreduction takes place.

8. Make the dye vat.

Mini Vat

Warm Water 120oF (49oC) 3 gallons (12 liters)

Unflavored Gelatin powder 1 tsp (2 gm)

Synthrapol 1 tsp (5 ml)

Clear Household Ammonia 2 Tbl (30 ml)

Thiox 1 tsp 4 gm)

9. Measure warm water into dye pot. Use non-reactive metal such as stainless steel orun-chipped enamel as your dye pot.

10. Mix the remaining ingredients in the order listed above making certain each item isthoroughly mixed before adding the next.

11. Add reduced stock solution by carefully lowering the container into the dye vat andsliding the liquid out at an angle. Stir gently.

12. After 30 to 60 minutes the vat should be clear greenish-yellow with a shiny, dark

blue metallic surface. The vat is now ready to use.

13. Maintain a 120oF(49oC) temperature throughout the dye process. Soak your wool forat least 15 minutes in 1 gallon (4 liters) of 120oF (49oC) water with 1 tsp (5 ml) ofSynthrapol. The wool should sink in the Synthrapol soak, not float. Squeeze out excesswater evenly from the wool. Gently push the dark blue scum aside before putting yourwool into the vat. Wool that is not thoroughly wet carries large quantities of air whichquickly oxidize the reduced Indigo and destroy the vat.

14. Soak the wool in the dye vat for 30 minutes with gentle, intermittent stirring, makingsure all the wool remains below the surface of the vat.

15. After 30 minutes, remove the wool, squeeze excess liquid back into the vat whileholding the wool close to the surface to avoid introducing air into the vat.

16. Let the wool oxidize (turn blue) for approximately 15 minutes.

17. Repeat dipping and oxidizing until the desired depth of blue is obtained.


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18. After the final dip and the fiber is fully oxidized, gently wash the wool in a warm120oF (49oC) water bath for 10 minutes in a generous bath of Ivory bar soap or IvoryFlakes. With a knife, its easy to flake off a 1/8 inch thick peel of soap. Gently stir thewash bath occasionally and rinse the fiber until the water runs clear.

Then soak the wool for 10 minutes in a bucket of acid soak. Make the acid soak bymixing 2 Tbl (30 ml) of White Distilled Vinegar in 1 gallon (4 liters) of room temperaturewater. Then rinse the wool thoroughly in plain water and hang to dry.

Copyright 2002

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color-wash-fastness-and-fashion-effects/

Indigo Dyeing Methods Engineering Color, Wash Fastness And Fashion Effects

Indigo Dyeing

Indigo dyeing is unique and because of the complex chemical reactions should be correctly

viewed a a form of chemical engineering.

Only Indigo dyeing requires multiple dye applications for a dark shade.

Color consistency of Indigo in recent decades has been unsatisfactory as a result of machine

designs that do not apply basic principles of fluid mechanics properly and unstable dye mixes.

Commonly, a single dye lot will have between 8 and 15 visually different shades from beginning

to end and also have shade differences from one side to the other.

Indigo Dyeing Methods

Indigo dyeing follows the same basic steps regardless of machine design.

Scour or dye bottoming in a heated tank,

washing tanks, dyeing(1-20),a heated tank for topping (optional) and wash tanks.

In different areas of the world,the same color is produced using 1.8, 2.0 or 4% Indigo depending

on dyeing method.
http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/http://morrisontexmach.com/welcome.cfmhttp://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-methods-engineering-color-wash-fastness-and-fashion-effects/


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Dark Indigo(1.8%) 1. 15% caustic cold2.Wash 60C

3.Wash 60C

4. Wash cold

Drying cylinders hot

Steamer cold

Boxes 5-12 Indigo

Steamer cold

13.Wash 50C

14. Wash 50C

15. Wash 50C

16.Wash 50C /Softener

Stock Mix 80 g/l Indigo

Pure 100 g/l 50% Caustic

70 g/l Hydro powder.

Chemical Feed 120 g/l 50%

caustic 60g/l Hydro powder

Feed 1.4 liters per minute

Dark Indigo Color

This was an example of a typical method used in the U.S. for a very dark shade.

In order to produce the same depth of color as 1.2% in the U.S., in Latin America 2.0% is used

and in Asia from 2.4 to 2.8%.

The U.S. method results in more surface (ring dyeing), which loses color faster.

Darkest Indigo Shades

Very dark shades of Indigo are in demand currently around the world.

Many companies use 4% or more Indigo on weight of yarn, which is expensive.

2% Indigo will produce the same depth if low levels of caustic are used(0-0.4%)

For dark Indigo that does not lose color 2% applied normally, with an Indigo bottom.
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Light Indigo Shades

Dyeing Indigo in light shades results in asky-blue impossible with any other dye.

This is useful for shirting fabrics that are not strong enough for stonewashing, bleaching or

cellulase treaments.

Special procedures are necessary in order to avoid colorfastness problems.

Light Indigo 0.4% 1. 4% caustic 90C

2.Wash 60C

3.Wash 60C

4. Wash 60C

Bypass drying cylinders

Bypass steamer

Close off boxes 5-8

Boxes 9-12 Indigo

13. Wash 50C

14. Wash 50C

15. Wash 50C

16.Wash 50C/softener

Control Of Sulphur Bottoming

The typical methods used for dyeing sulfur bottoms result in denim shade differences.

When applied as light colors, sulfur dyes should be dyed at temperatures


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Sulfur Bottom 1. Pad sulfur(cold)

Steamer hot

2.Wash cold

3.Wash 50C

4.Wash 50C

Boxes 5-10 Indigo

11. Indigo or wash 50C12. Indigo or wash 50C

Bypass steamer

13. Wash 50C

14. Wash 50C

15. Wash 50C

16.Wash 50C or softener

Sulphur Topping

In topping the sulfur dye is applied after the Indigo dyeing.

Sulfur topping permits much darker color than a sulfur bottom , but is duller.

Sulfur topping colors include black, blue-black, yellow brown and green.

Sulfur toppings are used to produce slub appearances in normal yarn.

Sulfur Top 1. Pre-wet 2% caustic 90C2.Wash 60C

3.Wash 60C

4. Wash cold

By pass drying cylinders
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Bypass steamer

Boxes 5-10 Indigo

11. Wash 60C

12. Pad sulfur topping

Steamer hot

13. Wash cold

14. Wash 50C

15. Wash 50C

16.Wash 50C/Softener

Reactive Dyes in Indigo Dyeing

Reactive dyes can be applied on specially-Designed Indigo machines.

Small 150 liter boxes are inserted inside the larger dye tanks for Indigo and sulfur.

Steamers, drying units near the front of the machine and high-quality dye padders are required

for quality dyeing.

Pad-Dry Chempad- Steam

Reactives

1. Pre-scour wetter plus chelate

90C

2.Wash 50C

3. Pad monochlortriazine dye

cold, neutral pH

Drying cylinders hot

Pad caustic in salt brine

Steamer hot

Bypass boxes 5-10

11. Soap 90C

12. Soap 90C

Steamer hot

13. Wash 60C

14. Wash 60C

15. Wash cold

16.Wash cold/softener
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Pad Steam Reactive Topping 1. Pre-wet 10% caustic 90C

2.Wash 60C

3.Wash 60C

4. Wash cold

By pass drying cylinders

Bypass steamer

Boxes 5-10 Indigo

11. Wash 60C

12. Pad Dichorotriazinyl cold

with bicarbonate

Steamer hot

13. Wash cold

14. Wash 50C

15. Wash 50C

16. Wash 50C / softener

Control Of Indigo Dyeing

The Indigo dyeing process begins with a concentrated mixture of Indigo, sodium hydroxide and

reducing agent. This concentrated mixture (70-90 g/L Indigo) is delivered by pipes to the

Indigo dye tanks where the dye concentration is reduced to 1-4 g/L for dyeing the cotton.

Dye Mixing Procedures

Many denim companies find it difficult to control original and washed Indigo shades.

The primary source of color differences is the instability and inconsistency of Indigo mixtures.

As the concentration of reducing agent going to the dye machine changes, the color changes.

Uniform Indigo Mixtures
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For consistent Indigo dyeing, the mixture must have consistent concentrations of Indigo, sodium

hydroxide and reducer from the top of the mixture to the bottom.

The main cause of inconsistent Indigo mixtures relates to concentration levels.

Instability of Indigo mixtures results from the decomposition of sodium hydrosulfite.

Consistency of Concentration

There is a limit to the amount of any chemical that can be dissolved in water.

When the limit of solubility of any chemical In water is exceeded, precipitation occurs.

Indigo mixes should not have more than 20% solids. At higher levels, chemicals and dye sink to

the bottom of the tank.

Improving Dyeing Consistency

When reducing agent sinks to the bottom of the tank, there is a higher concentration than in

the top of the tank. As the dye enters the machine, the higher concentration results in a lighter,

greenercolor and as the dye from the top of the tank enters the machine, the color is darker and

redder.

Dye Control In Feeding Tank

Stirring the tank for 2 minutes will improve dye uniformity between top and bottom.

To avoid settling of dye and chemicals the total solids should not exceed 20%.

The glass plate test can be used to test concentrations of hydrosulfite in the top and bottom.

If dye requires 50 seconds to oxidize, there is about 50 g/L of reducer.

Buffers In Indigo Dyeing

Alkaline buffers have been used to make very dark shades of Indigo with as little as 1% dye ,

more ring-dyed, faster fading.

Reductive buffers can eliminate color differences in Indigo-dyed denims and can reduce

hydrosulfite use by 30-50%.

Indigo Dyeing Problems And Potential -Part 1

October 24th, 2011 by Harry Mercer | Filed underManufacturing Process.

This is a highly technical article on Indigo dyeing by Harry Mercer. Read on if you are technically

oriented..

This is the first of a series of 4 articles addressing the problems and potential of Indigo dyeing. The

Indigo color is the principal source of the almost magical appeal of denim. The dyeing process is

unique among all methods of commercial dyeing, with the unusual design that is necessary for cotton

dyeing with Indigo. Indigo has been used for thousands of years, principally on wool and silk
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fibers for which Indigo is more suitable The difficulties in dyeing cotton with Indigo are apparent

with the numerous different shades that result, up to 15 per dye lot and also with side-center side

variation. Elimination of this variation has been accomplished, but it requires a deep understanding of

the unusual variables of Indigo dyeing. The 2 keys to success in manufacturing denim is firstly the

dyeing, then the finishing, both of which are more complex to conduct at a high level of quality. The

failure of most denim companies to overcome the challenges in denim wet-processing is the reason

why they are held hostage to low profit margins.

Part 1 of 4 MACHINERY

Indigo dyeing is a unique process that makes denim special and distinguishes denim operations from

all other types of cotton fabrics. No other method of cotton textile dyeing requires the multiple

application of dye to achieve a dark color, thousands of liters of dye bath, slow production speeds and

extremes of color variation and color-fastness. Indigo dyeing has been conducted without these

problems. The 2 most significant sources of Indigo dyeing are the

control of chemical concentrations, which will be addressed in future articles, and

the machine itself.

Machine factors that affect Indigo dyeing results

1) Circulation system design: Indigo dye in its reduced form consists of dye particles that have

been partially solubilized and exists in the form of charged colloidial particles. Colloidial dispersions will

sink due to the influence of gravity and require some agitation to keep them uniformly dispersed in

the dye box. If sample are collected from different parts of an Indigo dye box(top, bottom, front and

back), the concentrations are usually different. The uneven distribution of dye in the box as the

machine operates contributes to color variation. For many years, BASF, a leader in indigo dye for most

of the 20thcentury, recommended that the volume of the dye box be turned over 2 or 3 times an

hour. This means that if the box volume is 2000 liters that 4-6000 liters of flow into and out of

the dye box is needed to prevent low concentrations in part of the box and high in others. Indigo

machines produced in recent decades have been furnished with pipes that are too small to deliver the

right kind of flow. In terms of Reynolds number , the flow should be slightly beyond laminar, in the

low transitional range to ensure uniform disper-sion while avoiding turbulence that would destabilize

the dye. Also, for uniform dispersion of Indigo, the entry line should be positioned in the yarn exit side

of the box near the top, while the exit line should be at the yarn entry side near the bottom. Many

Indigo machines have the dye entry line on one side and the exit line at the yarn entry, which is a


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cause of cross-shade variation.

2) Dye box design: In a previous article I discussed the effect of dye box design on the color

consistency of Indigo. In most indigo machines the box design is responsible for massive losses

of hydrosulfite at the surface of the dye boxes during operation which results in economic losses as

well as variations in hydrosulfite concentrations in the machine which leads to color variation. The

principle is known as Specific Surface Area which means that the larger the surface area of the

Indigo box to the volume, the faster the hydrosulfite is lost. So, in a 2000 liter box with 2 square

meters of surface area , the hydrosulfite will decompose at twice the rate of a 2000 liter box with 1

square meter of surface area. The total hydrosulfite losses in a typically larger box of a rope range will

average around 15%, while in the smaller boxes of a typical sheet range the losses will be from 45-

70%.

3) Tension Control: High yarn tensions on continuous Indigo dyeing machines has 2 significant

effects- the yarn loses strength and the ability of the dye to penetrate the cotton fibers is reduced.The loss in yarn strength results in higher warp breaks in weaving, meaning lower efficiency and

higher weaving off-quality. The reduced penetration of Indigo into the fibers results in rubbing

fastness problems and a higher per cent Indigo on weight of yarn for a specific depth of shade.

4) Immersion time: Indigo dyeing is a form ofwet-on wet processing. The yarn is normally

scoured and washed before entering the dyeing section, which means that it is already wet. In order

for the Indigo dye to enter the wet yarn efficiently a process known as liquor exchange is

necessary in which the Indigo dye/water displaces the water already in the yarn. This is a slow

process and the longer the immersion time , the more easily the dye penetrates into fibers and yarn,

resulting in better colorfastness and darker color. Until the 1970s, Indigo machines operated at

speeds of 12 meters per minute through the much larger boxes of rope ranges, so the immersion time

was 2-3 times longer than on modern sheet ranges. The dye penetration was complete which resultedin the darkest possible color with 3% Indigo and that would never fade.
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http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-problems-and-

potential/

Indigo Dyeing : Problems And Potential

Part 2November 11th, 2011 by Harry Mercer | Filed underManufacturing Process.

This is a guest post by Harry Mercer on Indigo dyeing. It is second part of the article in series. The

first part can be seen by clicking here

Preparation For Dyeing

In the previous article, the basic machine factors in

Indigo dyeing were discussed. There are many other

details required to achieve the highest quality Indigo

dyeings , but ultimately the most important factors

involve the preparation of Indigo and chemical feeds to

the machine. Approximately 80% of Indigo dyeing

control depends on the stability and consistency of the

dye and chemicals being sent to the machine.

1) Raw materials: The basic ingredients for Indigo dyeing are the Indigo dye, sodium hydroxide and

the hydrosulfite (sodium dithionite). Indigo is an insoluble vat dye which means that

it cannot enter the cotton fiber until it is made soluble by the process of reduction

.Reduction is basically a process where hydrogen is produced which opens up the

Indigo dye molecule allowing it to attach to a water molecule which carries the vat

dye into the fiber. The most commonly-used

2) The reducing chemical is known as sodium hydrosulfite, but this

nomenclature is incorrect because the molecule does not contain hydrogen. The

hydrosulfite acts on the sodium hydroxide to split it into NaO and hydrogen, both of

which attach to the dye molecule in the reduction process.

3) The reduction of Indigo with sodium hydroxide and sodium dithionite is known as

vatting and has been used for thousands of years. Vatting refers to mixing the dye and chemicals into

a tank or vat with some stirring and then waiting from 1-4 hours usually for the complete reduction

of the dye to occur which is noted when the solution color is a clear, yellow-brown.. The solution then

is referred to as leuco Indigo, a Greek word meaning without color. The concentrated Indigo mix

is then ready to pump into the dye machine for dyeing.

4) Most of the variation in Indigo dyeing is a result of instability in this concentrated mix. Sodium

dithionite can be extremely unstable,

with the concentrations in this feeding

mixture becoming smaller with the
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passage of time. For example, the initial recipe may specify 100 grams per liter of sodium dithionite,

but by the time the last liter goes into the machine, the concentration often drops to 20 to 30 grams

per liter and each 5 gram per liter loss in dithionite concentration produces a small Indigo color

variation. This is evidenced in many denim operations that suffer 10-15 colors after fabric washing

per dye lot.

5) There are several causes for the decomposition and strength losses of the reducing agent in the

feeding mix: Oxidation at the surface of the tank, unnecessary stirring and high concentrations of

ingredients. The stirring should be only enough to maintain consistent concentrations of dye and

chemicals from the top of the feeding tank to the bottom. Stirring beyond that will result in more

reducing agent being oxidized. Also, in many Indigo operations the stirring units are badly designed

with small propellers that turn at high speeds. The Indigo feeding mix is of very high viscosity and in

order to stir the entire mix out to the edge of the tank, large propellers that cover the tank diameter

are needed. These stirrers should turn at only 10-15 RPM in order to avoid turbulence that would

lower the strength of the mix. With regard to concentrations, if the viscosity of the dye mix is too

high, the reduced Indigo will not disperse uniformly resulting in areas of varying concentration in the

tank that will cause color change as the mix is fed to the machine. Concentrations above 23% solid

have a tendency to settle, so that there are very high concentrations of reducer in the bottom of the

tank, making a greener Indigo tone when pumped to the dye boxes, and lower concentrations of

reducer at the top of the tank, making a redder Indigo tone later in the dyeing. No more than 80

grams per liter of indigo should be added to a feeding mix as this is the maximum amount that

has long been proven that can be completely reduced. The amount of reducing agent should also be

limited to 80 grams per liter since greater amounts will cause more rapid decomposition due to

aerobic and anerobic decay.

6) The concentrations of indigo and reducing agent must be actively managed so that the same

concentrations of dye and reducer are feeding to the machine every minute,otherwise the color will

change. Management of the feeding mix requires an understanding of the chemistry of reduced dye

solutions, measurement of concentrations and skill in correcting strength losses of ingredients in the

feeding mix especially of reducing agent and alkali. There are 2 simple , but special test methods

to measure the concentration of alkali and sodium dithionite in the feeding mix: a 2-endpoint

titration for alkali and the glass plate test which have been in use by the best denim companies for

over a century and will be covered in a future article.

Conclusion:

The problem of Indigo color variations is principally a result of inconsistent dye and chemical

concentrations going to the machine. A glance at the design of flow of dye and chemicals into Indigo

dye machines should make this obvious. The multiple dye box arrangement and circulation in the

dyeing section of indigo machines allow the blending of indigo and reducing agents, so the problem of

variation obviously starts at the mixing tank.

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Indigo Dyeing With Loop Dyeing MachineryNovember 4th, 2010 by Harry Mercer | Filed underManufacturing Process.

The name Loopdye results from the method of skying or air passage for oxidizing the Indigo-dyed

yarn and the method of passing through the Indigo dye. On the other 2 important Indigo machine

types, the dyed yarn is passed through from 6-8 Indigo boxes on rope machines or 6-20 Indigo boxes

on slasher (sheet) Indigo machines, multiple dye boxes being necessary for dark shades because only

a small amount of Indigo can be applied in each immersion. After immersion in each Indigo dye box,

the yarn is conducted through the air after each box, where the reduced Indigo (yellow-green) is

oxidized or fixed by oxygen in the air returning to the original blue, then the yarn enters the next

dye box, passes into the air and so forth until the required depth of shade is developed.

In the case of rope and sheet ranges, this oxidation takes place above each dye box. In the Loopdye

process, there is only a single Indigo box through which the yarn passes 4-5 times. The white

cotton is pulled into the front of the machine and passes first through the pre-treatment boxes, then

moves through a reactor which can be used for steaming or additional reaction time for sulfur-

bottoming or Mercerization, followed by washing. The wet yarn then enters the Indigo dye box. When

the yarn exits the dye box, instead of moving forward, the yarn is carried to the rear of the machine,

around the top and rear of the yarn creel from where it started, passes under the yarn creel where it

is returned to the Indigo box for another dye passage. This continuous passage of yarn between

the yarn creel and the dye box is in the form of a loop which is almost circular. After

making multiple loops through the Indigo dye box the yarn is conducted through wash boxes and on

to drying cylinders. The Loopdye machine is a simplified version of a sheet or slasher Indigo

machine. After drying the Indigo-dyed yarn, the yarn passes directly to sizing where the yarn isprepared for weaving. Because the sizing part of the machine must stop in order to remove a

completed weaving beam, in order to prevent the dyeing unit from stopping as well, there is a yarn

accumulator between the drying cylinders at dyeing and the wet-size boxes. When the yarn stops

moving on the sizing unit, a series of parallel cylinders begin to move apart allowing the yarn from the

dye unit to continue through dyeing and allows the size machine approximately 2 minutes of time to

install an empty weaving beam and re-start the sizing machine.

Loopdye Machines in the Denim Industry

In the early 1990s, thee were approximately 30 Loopdye machines in use. Currently, the number is

reported to be 60 or so. The biggest concentration of these machines is in Brazil. Vicunha employs 11

of these machines, Canatiba, Santana and Cedro have 2 units each, while Tavex, Tear, TextilKafi, Santista have 1 each. There are 9 of these machines that have been equipped with

nitrogen units which use nitrogen gas as protective blanket over the surface of the Indigo dye. The

nitrogen gas prevents oxygen in the air from attacking sodium hydrosulfite resulting in more

consistent dyeing and reducing consumption of hydrosulfite, lowering costs and pollution. There are

other claimed advantages such as higher speeds and darker Indigo color.

Advantages and Disadvantages
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1. Productivity When compared to a multi-box slasher machine, productivity is essentially

equivalent since the yarn loading, start-up times and speeds are similar. Rope dyeing machines

can produce up to 4 times as much dyed yarn.

2. Capital Investment The Loopdye machine has the lowest initial costs of continuous Indigo

dyeing machinery, currently reported to be approximately 25% less than 8 dyebox slasher

machine.

3. Operating Costs Maintenance and energy costs are reported to be approximately 20% lower

with Loopdye when compared with slasher dyeing and even lower than with rope dyeing.

4. Space requirements The Loop machine with a single dye box requires less floor space than

either sheet dyeing or rope dyeing. Rope machines also require higher ceilings because of the

design of the airing arrangement.

5. Indigo Dyeing Quality The newer designs of Loopdye are reported to have little of the

problems with Cross-Shade (side-to-side) shading than with slasher dyeing equipment. Indigo

consistency from the start-to-finish of dyeing can be expected to be better with the inclusion of

nitrogen units. Rope machines still have an overall advantage in terms of Indigo dyeing quality,

but this may be overcome by employing improved chemical blending.

6. Sulfur dyeing The Loopdye machine can be equipped with a steamer for cold-pad sulfur

bottoming which will provide greater consistency than a hot application in the 1st box. The Loopmachine is not provided with enough boxes after Indigo dyeing for sulfur topping as the slasher

dyeing is. With the newer methods for cold-sulfur dyeing, the Loop machine is ideal for sulfur

colors since it the dye can be applied in only one box, which allows for faster color changes and

less dye discarded after the dye lot is finished. Rope machines still have the greatest flexibility

with regard to producing a full range of denim colors.

7. Weaving Efficiency The methods of dyeing, especially of sulfurs, has a direct effect on warp

yarn breakage in weaving, which lowers operating efficiency as well as fabric and garment

quality. Experience with the older design of Loopdye machines demonstrated higher levels of

warp breaks in weaving than other Indigo machines. Rope dyeing results in the lowest-level of

weaving stops, largely because yarn breaks in dyeing can be repaired at long-chain re-beaming.

8. Versatility In the higher denim fashion market, some companies like Vicunha have hadsuccess using a combination of Loopdye and slasher dyeing. Overall, the slasher dyeing with its

greater number of application boxes offers more flexibility in product development, while rope

dyeing provides the greatest flexibility for denim product development.


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http://www.denimsandjeans.com/denim/manufacturing-process/indigo-dyeing-with-loop-dyeing-

machinery/

Rope Dyeing Vs Slasher (Sheet) DyeingMay 19th, 2011 by Harry Mercer | Filed underManufacturing Process.

This is a guest post by Harry Mercer

Until 1915, most Indigo dyeing was conducted in skein machines for cotton or loose fiber dyeing for

wool. Skein dyeing of Indigo is still the best method for dyeing Indigo on very fine yarns for the

delicate high-fashion fabrics. In 1915, the first rope dyeing machine appeared and only in the 1970s

was sheet dyeing introduced. The relative advantages of rope as opposed to sheet Indigo machines is

a common subject of debate. Based on my 30 years of experience in this area, including as a

consultant in about 40 denim operations worldwide, here are some basic observations that I have
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made in companies that had only sheet or rope dyeing, but also in many denim companies that

employed both. These evaluations included mass-balance studies, benchmarking, weaving efficiency

and overall fabric quality.

A. Lower consumption of reducing agent per kilogram of yarn.

The primary reducing agent utilized in Indigo dyeing is sodium dithionite, commercially known as

sodium hydrosulfite. The amounts of this reducer that are consumed in Indigo dyeing are greatly in

excess of what is necessary for the Indigo dyeing itself. In explanation, in order to reduce 100

kilograms of pure Indigo so that dyeing can proceed, only about 66 kilograms of 100% hydrosulfite

are required for the basic reaction. The amount of hydrosulfite actually consumed in Indigo dyeing is

often3 or 4 times this amount. There is often hydrosulfite wasted incurred in the initial mixing of the

stock mix, due to excessive stirring or concentrations ofhydrosulfite greater than 80 grams per

liter which promotes anerobic decomposition.

A great deal of hydrosulfite is lost because of contact with atmospheric oxygen at the surface of Indigo

dye boxes as a result of aerobic decomposition. The surface losses of hydrosulfite are related to

the volume and surface area of the dye boxes, with approximately 15% loss in larger Indigoboxes found on rope ranges and 50% or more in the smaller dye boxes found on sheet ranges.

The scientific explanation for this phenomenon is related to what is known as Specific Surface Area

(SSA). The greater the SSA (the quotient of the surface area and volume), the more rapidly the

sodium hydrosulfite is oxidized. The time for half-oxidation (50% loss) is inversely proportional to the

SSA, which means that decomposition is slowest in a large dye tank with a relatively small surface

area. There are other factors involved such as the initial concentration of hydrosulfite in the dye boxes

a higher initial concentration decomposes more slowly. However the most significant source of loss

is through surface contact and air brought into the dye tank by yarn.

The instability of hydrosulfite in smaller Indigo boxes is also the primary cause of color variation in

Indigo dyeing, which on rope ranges is much better controlled. It should also be noted that roperanges have the advantage in regards to Cross Shade Variation(CSV), which refers to differences in

color from side-to-side in the fabric. CSV is basically a result of dye circulation system design where

the Indigo enters the dye box from the side instead of the front. In rope ranges that are designed with

that style of circulation there is also some difference in the yarn color from to side-to-side, but unlike

sheet ranges where the yarns are fixed in their final fabric position, the yarn ropes can be blended to

remove the side to side effects. There have been some newer designs of Loop indigo machines which

have greatly improved CSV.

B. VERSATILITY IN DENIM PRODUCT DEVELOPMENT

Rope ranges have been designed to apply the widest range of dyeing techniques. For example, the

Spectrum Dye Machine available fromMorrisoncontains features like additional steamers and drying

sections that allow not only the standard dyeing techniques of sulfur bottoming and topping, but also

consistent application of all other cotton dyes such as vats, reactives and directs in combination with

Indigo or dyeing yarns with these dye classes only.
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Also available are specially designed dye boxes that allow the simultaneous dyeing of 2 different sulfur

applications, such as one set of yarn with a sulfur topping and the other set without topping, or with

only a sulfur color, which allows flexibility in production. Rope ranges are also easily adaptable for

random effects such as space dyeing of yarn. With the rope design, yarns from different dyeings such

as Indigo only and sulfur only, can be blended for producing stripe patterns.

C. HIGHER PRODUCTION AND FABRIC QUALITY

Common methods of operating Indigo machines have a damaging effect on yarn quality which results

in very high warp breaks in weaving, lowering efficiency and increasing off quality. Yarn on the

machines is made weaker as yarn tension increases. Sheet Indigo machines, because they are

attached to size machines, have very high levels of yarn tension and therefore higher weaving

breaks than yarn dyed on rope ranges. A yarn quality that would result in 10 warp breaks per million

weft insertions without Indigo dyeing often will have around a break level of200 with sheet dyeing,

but as low as 15 if processed on rope machines . This is because tension on rope machines is

much lower and can be easily controlled at very low levels.

Another important cause of high weaving breaks in denim is dirty yarn the cleaner the yarn the

higher the weaving efficiency. This is because chemicals not washed from the yarn after Indigo dyeing

result in bad sizing and lower protection of warp yarns. Wash boxes on rope ranges are typicallymore efficient than the smaller wash boxeson sheet ranges that use overflow washing

methods. The importance of washing the yarn dictates that it is better not to apply softeners in the

final box for rebeaming efficiency which is optimal though improved washing and moisture control

after drying.

The need for a separate rebeaming step in rope dyeing is often considered objectionable in rope

dyeing, but this is actually an important advantage, since yarn breaks can be repaired at rebeaming
mailto:[email protected]?subject=IRDR%20Wash%20Dye%20Box%20:%20Denimsandjeans.commailto:[email protected]?subject=Spectrum%20Dyeing%20Machine%20:%20Denimsandjeans.commailto:[email protected]?subject=IRDR%20Wash%20Dye%20Box%20:%20Denimsandjeans.commailto:[email protected]?subject=Spectrum%20Dyeing%20Machine%20:%20Denimsandjeans.com


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resulting in higher weaving efficiencies. Yarn breaks from warping and dyeing cannot be

repaired in sheet machines because they are passed directly from dyeing to sizing.

D. FLEXIBILITY IN PRODUCTION

Sheet ranges are usually limited to producing yarn for only 1 weaving set at a time. In a rope range,normally 12 ropes will produce enough yarn for a weaving set and because rope ranges do not pass

the yarn directly to the size machine, from 1 to 50 ropes can be dyed at one time. Any

combination of yarns can be processed for completely different fabric constructions at the same time

and dyed with the same Indigo color. Also, rope ranges can be operated continuously without

stopping, which avoids the waste of yarn which occurs when sheet ranges must stop in order to

change yarn lots. Because the yarn is sized separately.higher priority fabric orders can be processed

without delays resulting from the need to complete a dye set as with sheet dyeing.

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dyes & pigmentsB2B MARKETPLACE

Manufacturers Directory|B2B Trade Offers|Trade Fairs & Events|Global Dyestuff Industry

Colour

Index

Dyes Pigments

Applications

Machinery

Glossary

FAQ's Buyers

Guide

What is Dye | Types of Dyes | Dye House | Dyeing Process | Dyeing Machinery | FAQs on

Dyes | Buyer's Guide to Dyes

Dyeing Process basically discusses what you do with the dyes. There are today available latest and state-of-

the-art dyeing methods that effectively colour the various substrates. This is a very critical operation carried out

in the Dye houses in a series of steps. The pages here gives precious information regarding the various dyeing

processes in different industries.

Buyer's Guide to Dyes

Buyers Guide to Dyes

Buyers Guide to Pigment

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Dyeing Process Continuous Dyeing Process

Batch Dyeing

Process

Continuous Dyeing

Process

Semi-continuous Dyeing

Process

Pigment Dyeing

Process

The working of a continuous dyeing process is described here. The textile substrates are feeded continuously into a

dye range. The speeds can vary between 50 to 250 meters per minute. According to Industry estimates Continuous

dyeing is a popular dyeing method and accounts for around 60% of total yardage of the products that are dyed.

A Continuous dyeing process typically consists the following. Dye application, dye fixation with heat or chemicals and

finally washing. Continuous dyeing has been found to be most suitable for woven fabrics. Mostly continuous dye

ranges are designed for dyeing blends of polyester and cotton. The step of padding plays a key role in the operation

of continuous dyeing. Sometimes Nylon carpets are also dyed in continuous processes, but the design ranges for

them is unlike that for flat fabrics. Warps are also dyed in continuous process. Very good examples of such warp

dyeing are long chain warp dyeing and slasher dyeing using indigo.

A continuous dye range has been found useful and economically sustainable for dyeing long runs of a given shade.

One important factor that separates continuous dyeing from batch dyeing is the tolerance factor for color variation.

That is more for continuous dyeing as compared to batch dyeing. This is so because of two reasons a) the speed of

the process. b) presence of a large number of process variables which affects dye application. The process that is

illustrated below is designed for dyeing of blended fabric of polyester and cotton.

Some of the popular methods in continuous dyeing process are Pad-steam, Wet-steam, thermosol dyeing, TAK

dyeing, space dyeing, and pad-steam dyeing long chain warp dyeing etc.

Optimizing the Continuous dyeing Process
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Continuous and to some extent semi-continuous dyeing processes both are less prone to water consumption than

batch dyeing, but results in high concentration of residues. If some strict control measures are taken up it is possible

to reduce this losses of concentrated liquor. The following steps may prove useful.

Applying low add-on liquor application systems along with minimising of volume capacity of the dip through

when pad dyeing techniques are in operation.

Adoption of latest dispensing systems, where the chemicals get dispensed on-line as separate streams.

They gets mixed only at the moment just before the delivery to the applicator.

Using any of the following systems for dosing of the padding liquor. Important to know that it should be

strictly according to the measurement of the pick up:

o A proper measurement of the dyeing liquor quantity consumption in comparison to the processed

fabric. The resulting values thus obtained are processed automatically and applied in preparing the

next comparable batch.

o Application of the technique of rapid batch dyeing. Here the dyestuff solution is prepared just in

time, with steps that are based on on-line measurement of the pick up. This proves better than

those dyestuff that is kept prepared already for the whole batch before the commencement of the

dyeing batch.

To increase washing efficiency based on the proven principles like reduction of carry-over and counter-

current washing.

What gives Carpet its vibrant colour?

The carpets that you see in different colour and hues is dyed by a continuous dyeing. A

continuous dye range for carpet typically consist of a steamer and a dye applicator. Generally

acid dyes are used. Carpet manufacturers are very adept in application of dye for producingspecial color effects on their product. As a result of this, many variations of dye applicators exist.

Under normal circumstances, a very high liquor ratio is must to produce good quality dyeing of

carpet. Typically, application method is used to meter the dye solution into the carpet. Patterned

effects are produced when the stream of dye that is metered onto the carpet are momentarily

interrupted. Streams of variety color dyes are applied in different patterns to create those special

effects.

Site Designed and Maintained by Dyes and Pigments

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Continuous Processing of Cotton woven fabric: A general process sequence may be as below:
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PRETREATMENT PART:

1. Singe & Desize (Semi Continuous process)

2. Scouring or Boiling3. Peroxide Bleaching

4. Neutralization

5. Drying

6. Mercerising and washing off to a pH of 6

7. Neutralizing

8. Drying

9. Ready For Dyeing (RFD stage).

1. Singeing & Desizing:a. Recipe: Bactosol HC = 5 g/l

b. Common Salt = 5 g/l

c. Wetting Agent (100%)= 3 g/l

i. Do cold padding with the above chemicals, batch,

and keep rotating the batch for 8 hours;

ii. Desize washing in 4 compartments @

90mts/minute speed.

2. Bleaching (Continuous Process)-

a.Caustic Impregnation:

i. Recipe:

1. Caustic Soda = 70gram/liter

2. Lissopal D paste = 10 gram/liter

a. 4 dips1 nip @ 90 mtrs/minute speed.

b. Steaming @ 105C for 45 minutes in the steaming

chamber.

c. Cold Wash in 2 compartments (4 dips 1 nip) x 2

b. J-BOX Bleaching optional

i. Recipe:

1. Sodium Hypochlorite = 2 g/l Avl Cl2

2. Dwell time in J box 30 to 45 minutes at room temp.

3. No washing

c. Peroxide Impregnation:

i. Recipe:

1. Hydrogen Peroxide(50%) = 3 ml/liter


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2. Stabilizer = 0.5 gram/liter

a. 4 Dips1 Nip at cold.

b. Steam in Peroxide Steamer for 45 minutes.

3. Washing in 5 compartments with each 4 dip and 1 nip.

4. Dry and batch on A frame roller.3. Mercerisation: (Chainless Merceriser)

i. Recipe:

1. Caustic Soda = 280 to 300 gpl

2. Permenol N = 10 g/l

a. Cold Padding Speed:

i.

Bleached Fabric = 25 mtrs/minute

ii.

Grey Fabric = 15 mtrs/minuteiii.

Scoured Fabric = 20 mtrs/minute

b. Mangle Pressure: 3.2 to 4 kg/cm2

c. Liquor Pickup : 110%

d. Recuperation:

i. 1st compartmentstrength = 8 to 27 gpl

ii. 1st

compartmenttemp = 90 to 95C

iii. 2nd

compartmentstrength = 1.6 to 6.4 gpl

iv. 2nd compartmenttemp = 65 to 95C

e. Wash Tanks:

i. T

ank 150 to 55C

ii. T

ank 2Acetic Acid Neutralizing

iii.

Tank 360 to 70C

iv.

Wetting Agent room temp

f. Final fabric pH5.5.to 6.0

g. Drying:


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i. F

abric is dried in cylinder or stenter and batched as

RFD.

4. Continuous Dyeing Method for 100% Cellulose:

a. There are 3 methods:i. PadDryChemical PadSteam

1. Dye Liquor Preparation & recipe:

a. Cotfix Dyestuff = x grams/liter

b. Wetting Agent = 2-3 gram/liter

c. Antimigartion agent = 8-10 gram/liter

d. Mild Oxidizing Agent = 5-10 gram/liter

2. Padding Temperature should be < 35C

3. Liquor Pick up% = 60 to 80

4. Chemical Pad Recipe:Dyestuff G/L Caustic Soda Salt (g/l) Soda Ash

(g/l)

< 20 Nil 200 20

3040 Nil 250 20

> 40 Nil 250 20

5. Chemical Padding Temperature < 35C

6. Liquor Pickup 70 to 80%

7. Steaming 45-90 seconds withSaturated steam (101 to

105) the steam should be free

from acid.

ii. Pad-Dry-Steam:

1. This is carried out on a padding mangle attached with either Hot

Flue or Flow Dried. To fix the dyestuff, the dried material is

steamed in the normal continuous steamer for 4 to 7 minutes at 100

to 103C.

2.

PAD LIQUOR PREPARATION for VS dyes:Dyestuff G/L 10 20 30 40 50 >50

Urea G/L 0~50 0~50 0~50 50~70 50~75 50~75

Sodium

Bicarbonate

G/L 5 10 15 15-18 20 20-25

Resist Salt G/L 10 10 10 10 10 10


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3. Take all the precautions and conditions mentioned for Pad Dry-

Chemical Pad-Steam.

iii. Pad-Dry-Thermo fix Process:

1. Here again there are 2 processes:

a. Soda Ash Methodb. Sodium Bicarbonate Method

PAD LIQUOR PREPARATION for VS dyes

Dye G/L 2 10 20 40 60

Urea G/L 15 30 45 60 80

Soda

Ash(OR)

G/L 8 12 17 25 33

Sodium

Bicarbonate

G/L 12 18 27 36 45

The material is padded in the above liquor at room temperature, dried & thermo fixed as follows:

Temperature Soda Ash

Process

Sod.Bicarnonate

process

100C 4-6 minutes 5-7 minutes

120C 2-4 minutes 3-5 minutes

140C 40-60 seconds 60-90 seconds

5. After treatment:

a. Overflow Cold wash in soapers 4 dip 1 nip in 2 compartments

b. Neutralization with Acetic Acid in the soaped at cold with 2 ~3 g/l Acetic acid.

c. Hot wash in one compartment (soaper) @ 80 , 4 dip 1 nip in

d. Soaping with 2 g/l of soaping agent (Sandopur RSK) at 90C

e. 2nd soaping with 1 g/l soaping agent (Sandopur RSK) at 90C

f. Hot Wash

g. Hot Wash

h. Cold Wash

i. Acetic Acid Treatment 1 g/l or Formic Acid treatment 0.5 g/l

j. Squeezed on the last mangle and either plaited or wound on a batcher and taken

for drying.


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Possible Faults that may occur during the above process and check points/rectification:

1. Tailing: The Alkalinity in the mercerized fabric would be un-uniform ranging

from 0.25 to 1 and above gram/liter due to inefficient recuperation. That

means more and more alkalinity would be carried over on themercerized cloth and that can be checked in lab by titration. Any

variation in the alkalinity of the mercerized fabric can show up through

the length by the dye affinity difference and that is tailing.

a. Check Point:

i.

Alkalinity of the mercerized cloth has to be

quantitatively checked in the lab at intervals of 500

meters. It must be uniform.

2. C/S Variationmay arise due to

a. Desizing Expression of the squeezing mangle is to be checked

at frequent intervals.

b. Caustic Impregnation - Expression of the squeezing mangle is to

be checked at frequent intervals.

c. Peroxide Bleaching:

i. S

team Pressure

ii. S

team Temperature

iii.

Time duration of the steaming are to be controlled.

ii. Mercerising Impregnation Mangle expression

has to be checked.

1. Recuperator Efficiency has to be checked at every 1000 meters.

2. Final Alkalinity of the mercerized fabric should be less than 0.25

g/l of caustic.

3. Soaper washingAcid for neutralization should be prepared in

volume and should be fed in to the neutralization tank

continuously.

4. To counter check, the fabric absorbency may be checked in the

center and the two selvedges at regular intervals.


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3. Face to back variation

a. Mangle Expression in the dye padding should be 70% and chemical padding

should be 80%.

b. Thermosol temperature difference between faces may result in migration ofdyestuff.

c. In a 2 dip 2 nip mangles, if the expression of both the mangle are not identical,

then back to face variation is possible at any stage, dyeing, finishing etc.

d. In stenters, if the hot air blowers are not functioning, there may be face to back

variation.

e. In jigger dyeing machine, out of the two bottom rollers, one is not rotating

properly then back to face variation is possible.

4. Specky Dyeing:a. Improper dissolution of dyestuff:

i. The quantity of the dyestuff is to be pasted,

say for 1 kg of dyestuff, 5 liters of soft water should be used for pasting.

Then 1 kg of urea is dissolved in 5 liters of water and this solution is

added in the paste and stirred well to make a uniform lump less slurry.

About 40 liters of hot water at 85C is added to the slurry which is kept

under a high speed stirrer. The hot water should be added slowly to the

rotating vertex of the dye slurry. The filter this dissolved dyestuff

through a fine gauze.

ii. Temperature of dissolution:

1. M-Brand = 50C

2. V.S = 80C

3. ME, XL, HE = 80C.

iii. The dissolved dyestuff may be spotted on a

filter paper - a uniform circle shows proper dissolution.

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Dyeing of Reactives by Exhaust Method
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DYEING OF REACTIVE DYES BY EXHAUST METHOD

REACTIVE DYES

EXHAUSTION PHASE

Primary Exhaustion Phase

Adsorption

Diffusion

Substantivity

REACTIVE DYES AND DIRECT COTTON DYES

Direct Cotton Dye

Reactive Dyes

Role of ElectrolytePartition /Distribution Coefficient and Degree of Exhaustion

Liquor Ratio

Temperature

Influence of pH.

Influence of Substantivity

Migration phase

Secondary Exhaustion

Hydrolysis of Reactive dyes

Typical Examples

REACTIVE DYES

Choice of Reactive class of Dyes has become indispensable for application of

colours on the cellulosics to provide bright range of shades with reasonably

good fastness features. No other class of colours can boast of the versatile

range of shades with unmatched brilliance, yet economically viable and cost

effective that this class of dyes can offer. Even as Reactive dyes are most

popular for dyeing solid shades it is equally sought after for various resist

and discharge printing styles, thanks to its suitability to be resisted ordischarged readily and effectively

The reaction mechanism is apparently simple in that on just altering the pH

after exhaustion, formation of covalent bonds between the reactive group of

the dye and the OH of cellulose proceeds. For the same reason of ready

reactivity with Cell OH groups, it reacts with Water also to get hydrolyzed in

which state the dye behaves no better than a direct cotton dye. The
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dyeing with indigo

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