Tuesday, February 07, 2006



WATER: Used as the dye vehicle.

SALT: Used to accelerate dyeing and to encourage the indigo to bond to the fibers.

THIOUREA DIOXIDE: Because of it's stability it is used instead of sodium hydrosulfite. Thiourea dioxide reduces the indigo. The action of the thiourea dioxide liberates the hydrogen, which combines with the indigo converting it to indigo white. In other words, the thiourea dioxide takes up the oxygen from the water, freeing the reducing agent hydrogen. The hydrogen reacts and joins with the double bonded oxygen in the indigo, forming a new series of internal bonds. It is sometimes said that it removes the oxygen from the dye bath.

In the presence of oxygen again, the two hydrogens attached to the indigo white molecule, leave the indigo white and return to indigo blue.

LYE: Known as caustic soda or sodium hydroxide. It functions as the alkali and dissolves the indigo white.  "Red Devil Lye" is no longer available and substitutes available in the stores give unsatisfactory results both in color and the behavior in the dye pot.  Lye for indigo dyeing can be purchased from Pro-Chemical and Dye Company, 1-800-2-BUY-DYE, and on the web at,   http://www.prochemical.com/catalog/indigo.htm

SYNTHETIC INDIGO: A manufactured indigo whose chemical composition is similar to natural indigo. It has a uniform quality and is richer in indican than natural indigo.

Indigo can dye any natural fiber with slight alterations in the procedure. Because of the extreme alkalinity of the indigo dye pot, wool and silk must be handled with extreme care. Both fibers should be dyed in a low alkaline bath and neutralized soon after oxidation.

SAFETY: Before starting, put on respirator with a filter that protects against organic gasses, goggles to protect eyes, and heavy chemical resistant gloves. Mix the indigo stock in a well-ventilated area.

During the summer the indigo can be kept outside, in a shady place. During the winter keep the pot in the warmest spot possible the place should have very good ventillation. If the pot does not work at room temperature you might have to purchase an immersion heater. A pet store sells aquarium heaters that work well for this purpose. The temperature should be between 90-110 degrees.

For a 44-gallon plastic garbage can: This size plastic garbage can is useful because of its depth and width. Thirty-six inch stenciled fabric can be dipped into the vat without crowding. The recipe can be adjusted to a more convenient size vat.


Indigo is insoluble in water. Fibers cannot be successfully dyed by indigo without assistants. The only way fiber can be dyed with indigo is through chemical reactions in the dye pot. There are two basic methods to immersion dye with indigo, reduction and fermentation

1. Reduction vat. This method involves using caustic chemicals such as sodium hydrosulfite (a reducing agent) and sodium hydroxide (an alkali). The addition of these two chemicals causes all the oxygen in the dye pot to be removed. The rapid utilization of oxygen and its removal from the dye pot causes free hydrogen. This hydrogen combines with indigo. When the fabric is dipped into the dye pot the indigo migrates onto the fabric. The blue color develops only after the fabric has been removed from the dye pot. Exposed to the air, the oxygen again locks onto the hydrogen rendering the color insoluble once more. The chemicals for this type of vat are quite caustic and potentially dangerous. Good ventillation is a must.

2. The second method of indigo dyeing is a more benign method. This method is quite lengthy and time consuming. In Japan indigo has been traditionally used in a fermentation vat. The Indigo plant is composted to remove the organic matter while preserving the dye. This composted plant matter is called sukumo. Sukumo has a high concentration of hydrogen producing bacteria necessary for fermentation. The indigo dyer only needs to provide "food" for the bacteria in the proper amount, at the proper time, at the proper temperature to make the dye work. Feeding the indigo dye pot is an art. Learning the skills to manage this type of vat can only be acquired by first hand experience. The konya-san (indigo-dyer) will use their fingers, eyes, nose and even the tip of their tongue to test the condition of the dye. The dye pot needs daily attention, constant temperature and takes on the aspect of a living being. The dye pot is often fed sake, oatmeal, or rice bran. In addition, an alkali leached from wood ashes is also added to the dye pot.  Many things can go wrong to stop the process.


Sprinkle 8 tablespoons thiourea dioxide onto the surface of 38 gallons of water. Mix gently, do not add bubbles.

Dissolve in a plastic bucket.

2 gallons water.
12 cups salt.
6 cups thiourea dioxidemust be added first.
Only after thiourea dioxide is disolved then the 4 cups lye should be added.  The lye should be dissolved in 8 cups (2 quarts) water.

Add each ingredient separately, stirring gently after each addition.

Add 8 to 10 cups (about 1 and 1/2 lbs to 2 lbs) indigo to the chemicals a spoon full at a time. Stirring after each addition. The indigo is very hard to mix with water, as it does not dissolve. It will take a few minutes to mix with the other chemicals. When completely mixed with the chemicals, the indigo will appear a dark yellowish-brown beneath the surface. The surface will be a dark coppery blue with lots of coppery foam. The foam is just oxygenated indigo that will be skimmed aside before dipping. Cover and let rest for 10 minutes.


Lower the bucket of indigo stock into the garbage can and empty it without splashing. Just gently let the indigo flow out into the water. Stir gently with a long wooden pole that reaches to the bottom of the pail. Let it rest for 1/2 hour. Then cover the dye pot with a piece of plastic by sinking the plastic down onto the surface of the indigo. This seals out all the oxygen. Fasten it around the rim with clothespins or a large bungee cord.

Skim aside the coppery foam before immersing anything into the indigo. The PH should be about 9.5-10, although the Japanese think the the best dyeing happens between 10.6 to 12.6

After each use, the dye pot should be covered with plastic that seals the surface of the indigo from interaction with the air. Make sure the depot is always covered after each use. This step is very important and will keep the dye pot strong for about two weeks of daily use.

If the pot has been used heavily it will get weaker with use. There will have been the introduction of oxygen and the dye pot will die. The indigo depot is dead when a glass of dye reveals nothing but blue particles. The dye should appear a yellowish-green. The pot can usually be revived at this time by adding more chemicals.


If more water is needed in the dye pot, the best time to add it is before this new round of chemicals.

Mix together:

2 quarts of water.
8 teaspoons thiourea dioxide (reducing agent, used instead of sodium hydrosulphite because of its stability).
8 teaspoons of lye (alkali, caustic soda, sodium hydroxide)

Add to the indigo dye pot. Check the color with a glass. If there are any blue particles in the water, add another round of chemicals.

You can tell if more indigo is needed, by looking at the amount of blue particles or color in the dye pot. If more indigo is needed add another round of stock solution. You may also halve the amount of indigo and chemicals if you feel that there is enough indigo left from the previous batch.

Dipping apparatus: All fabrics and yarns should be washed before stenciling and dyeing. Put yarn on a rod, shirts, pants and other articles of clothing on a plastic hanger, fabric should be clipped with a clothes pin to a plastic hanger, yardage should be accordion pleated back and forth and clipped with clothes pins to plastic hangers. If the fabric has a tendency to float up when dipping into the vat, attach fishing weights or clothespins to the bottom edge before dyeing.

Wetting-out: Wet-out all yarns and tie-dyes in water. The water in the fibers helps the indigo to move onto the fabric.  When the fabric is on the dipping apparatus, wet-out the fabric with a gentle spray from a hose.


1. Lower or slide the goods into the indigo vat. It is very important that this be done slowly and gently so as to not introduce any surplus air

2. The goods should be immersed in the dye for about 1 to 5 minutes depending on whether tie-dye, yarn, or pasted fabric is being dyed. Make sure the goods stay about 5 inches below the surface of the indigo. Do not raise and lower into and out of the vat.

3. Carefully raise the goods out of the vat and let it oxidize in the air. It will have a yellowish, than a greenish tinge when first removed from the dye. It will turn completely blue when oxidation is complete. It is not necessary to let the goods dry between dipping. If in a hurry it's a good idea to let the goods oxidize at least for one hour.  A good rule of thumb is to dip the goods once a day.  Except for tie-dye, it is important to hang up and open out the dyed goods.

The depth of color is obtained by repeated dipping into the vat after oxidation is complete. Lengthening the amount of time the goods are immersed will not darken the color. The amount of time between dipping depends on the amount of moisture in the atmosphere, the thickness of skeins, the type of fiber, etc. Usually 1 hour is a good amount of time for oxidation. The minimal oxidation time is 1/2 hour; some dyers feel that as much as one week between each dipping is not unusual.

Stenciled fabric can only be dipped 4 times before the rice paste breaks down. Tie-dye and yarns can be dipped as many as 6 or 7 times for a very deep blue.

RINSING: Indigo dyed fabrics should be rinsed in warm water until the water runs clear.

SOAPING: It is important to wash the indigo in a bath of hot water and synthrapol. This hardens the color.

BRIGHTENING BATH: Soak the fabric in a hydrogen peroxide / water mixture for 10 minutes. Add about 1/8 cup hydrogen peroxide to 1 1/2 gallons of water. This will brighten the indigo and make it seem to bloom. This step will make the indigo have a purple tint.

NEUTRALIZING BATH: Dip the fabric in vinegar water for 10 minutes. About 1/4 cup to about 1 1/2 to 2 gallons of water. The vinegar helps to neutralize the harsh chemicals. Rinse.

ANTI-CROCKING: Soak in a mixture of 10% liquitex to water for 10 minutes. Soaking in the liquitex mixture leaves a deposit on the indigo that will help to resist crocking. The liquitex soaking is not essential but nice. Do not rinse after this step. Dry.

CARE OF INDIGO DYED FABRICS: Do not wash indigo dyed fabrics in laundry detergent. Laundry detergent creates a similar environment as the indigo dye pot and will strip the color from the fabric. Use soap such as "Woolite", "Synthrapol", and “Joy" or "Palmolive" dish soap.

© Copyright M. Joan Lintault,