Dyeing with Indigo

Summer 2006
Cynthia Thayer of the Wednesday Spinners demonstrated dyeing with indigo
Cynthia Thayer of the Wednesday Spinners demonstrated dyeing with indigo at the 2004 Common Ground Country Fair.

“Two problems make indigo a dye unlike any other dye in the universe,” said Cynthia Thayer at the 2004 Common Ground Country Fair. It does not dissolve in water, nor does it adhere to material.

“It’s also the only natural dye that gives a real, true-blue color,” she added. Until the late 1800s, indigo provided the only way to get blue color into fibers. Today textile manufacturers still use indigo—although a synthetic form—to dye blue jeans.

Indigo does dissolve in alkaline solutions, such as those made with lye, baking soda, ammonia, urine or washing soda. Indigo is not necessarily a plant but a property of many plants, Thayer explained. Some sources of natural indigo include:

  • Indigofera tincoria from India
  • Indigofera suffruticosa from Mexico, the Caribbean and South America
  • Isatis tinctoria (woad) from Europe and Egypt
  • Lonchocarpus cyanescens from West Africa
  • Marsdenia (milkweed) from Sumatra
  • Nerium tinctorium (oleander) from India and the Far East
  • Polygonum tinctorium (Japanese indigo or buckwheat, which can be grown in Maine and is edible)

Woad grows in the British Isles and was used to make faces blue in the movie Brave Heart, noted Thayer. False indigo (Baptisia australis) has the property of indigo but not as strongly as some other plants.

Thayer went to a tiny island in the Caribbean many years ago, where indigo plantations had grown previously. There, Indigofera suffruticosa grew wild all over the island, even in cracks in the cement. She did some dyeing with it, and the local people were amazed; although they’d lived with the plant, they’d never seen it used.

At the Fair, Thayer used Polygonum tinctorium from her home garden to demonstrate dyeing with indigo. She had soaked the leaves in a bucket of water for about two hours. During the demonstration, she added baking soda to raise the pH, making the water alkaline so that indoxyl in the plant would dissolve and oxidize, becoming indigo. Four people poured the plant material and alkaline water from one bucket to another a few times to oxidize it.

Next, to make a dye that would adhere to fabric, the indigo solution was reduced by removing the oxygen from the pot. This changes the substance to “indigo white.” The reducing agent thiorea dioxide (also called Thiox or thiourea dioxide) removes oxygen and changes indigo to indigo white—“which will adhere to material, but it’s not blue, it’s white!” Thayer said. But when fiber is pulled from the vat, the dyeing solution oxidizes as soon as it hits the air and becomes indigo blue again.

When adding fiber or fabric to a dye vat, make sure it’s squeezed, Thayer advised, “because you don’t want to introduce air into the bath. Hold it together until it’s under the bath, then open it up. And wear gloves” if you don’t want your hands to turn blue. When you stir wool in the vat, do so gently. Likewise, when removing dyed fiber or fabric from the vat, put your hand under it and allow it to gently “float” out of the pot so that oxygen is not introduced into the reduced solution, Thayer suggested.
Because the indigo needs to be freshly cut to work well, and that used at the Fair had been cut a few days earlier, only a light blue resulted.

Urine can be used instead of baking soda and Thiox. “I have two 5-gallon buckets of urine at home,” Thayer explained. “I put about an ounce of that Salvadoran indigo [discussed below] into it, and it sits all summer. When I feel like dyeing something, I throw it in, half an hour later pull it out and it’s blue. The urine both provides the alkalinity that the indigo needs, and it ferments and therefore depletes oxygen in the solution. So with urine you only need one substance in there—and it’s free!

Indigo does not, like a lot of other dyes, need a mordant.

The chemicals used at the Fair were not toxic, but if you use lye, be sure to wear gloves, Thayer cautioned, since that is very caustic. Synthetic indigo is processed in a factory with lye and sodium hydrosulfite.

Easy to Grow

Japanese indigo “is so easy to grow that you put in 200 seeds and you get 200 plants. It never fails! Start the indigo late (about the first of May), because it’s very fast growing, and you can’t put it out until the danger of frost is over.” Transplant Japanese indigo to the garden at the beginning of June and harvest leaves at the end of August. “Don’t try to do any dyeing until the end of August, because for some reason, [the plant] needs to go through that heat of the summer before the color really comes.”

One Fairgoer noted that he’s had good years and bad years with the plant producing color. Thayer has noticed a big difference between harvesting the first week of August vs. the second week. “When it’s flowering is probably a good test of when to cut it. If you want to save seed for the next year, you have to cut [the plant] and bring it in, stick it in a bucket with water, and put it in the kitchen. It will [root and] start to flower, and in December it will have seed.” Maine doesn’t have a long enough season to produce indigo seed outdoors. One Fairgoer who grew it indoors all winter had it set seed in April. The plant is susceptible to an aphid, which flourishes in December but doesn’t seem to migrate to any other plants.

To obtain seeds of Polygonum tinctorium, send a self-addressed, stamped envelope to Cynthia Thayer, 51 Darthia Farm Rd., Gouldsboro, ME 04607.

Salvadoran Indigo

For the past few years at the Common Ground Fair, the MOFGA-El Salvador Sistering Committee has been selling indigo made by its sistering organization in El Salvador, where Indigofera suffruticosa and I. lepedezioides grow wild. Committee member Karen Volckhausen explained that MOFGA’s sistering groups in El Salvador are trying to revive indigo dye production, which was a huge industry there before the advent of synthetic dyes; historically the industry also exploited the cheap peasant labor force and was a toxic process. Today the sistering groups have developed a nontoxic method to extract the dye. “Businessmen from San Salvador have been drooling over the prospect of taking over the industry, but the people have held out to maintain small farmer ownership and production. It is known for its excellent quality–46% intensity, which is very high,” noted Volckhausen.

Thayer described the indigo from MOFGA’s sistering organizations as “really wonderful… Wool dyed with Salvadoran indigo and urine was a much different color, with a gray-green under the blue—a beautiful color; I love that color.”

Thayer was enthusiastic about dissolving the Salvadoran indigo cake in urine. “I take that cake and I take a little muslin bag. I take a hammer and womp the bag [to crack the chunks]—carefully, because you don’t want to break the bag.” The indigo doesn’t have to be too fine.

“You don’t have to do anything to it!” Thayer continued. “You have this pot, and it sits outside. You think, ‘Oh, I think I’ll dye a skein of this with indigo. You run out and throw it in [the pot].” She hangs the muslin bag over the side of the pot. “This is the best part: I pull it up every day and kind of massage it with my rubber gloves. I asked my apprentices to do that last summer, and they didn’t want to do it. I don’t mind it.”

Dyeing with Fresh Indigo
Time: About 4 hours

1. Pick 16 oz. of fresh indigo leaves, put them in a bucket and add just enough hot tap water to cover the leaves.
2. Heat the solution to 160 degrees F. over a period of two hours. Don’t heat it too quickly.
3. Strain the liquid and squeeze liquid from the indigo leaves into the strained liquid.
4. Add 2 Tbsp. baking soda to the liquid and stir a little.
5. Pour the liquid from one bucket to another for a few minutes, or until the solution turns dark green/blue. This oxidizes the dissolved indoxyl, changing it to indigo.
6. Dissolve 2 Tbsp. Thiox in warm water, pour it into the dyebath, cover and set the pot in a larger container of water that is just hot enough to keep the dyebath at 100 to 120 degrees F. for about an hour.
7. Meanwhile, soak 2 to 4 oz. of yarn in hot water.
8. When the dyebath has turned yellow, add the wet yarn—carefully, to minimize adding oxygen to the solution. Leave it in the dye for 20 minutes. Remove it gently and let it oxidize by hanging it on a wooden rack. The yarn will turn blue as it reacts with oxygen in the air.
9. Let the yarn dry for as long as it soaked in the bath. One dipping and airing is usually enough to richly color wool yarn, but for intense colors on cotton or silk, repeat the soaking and airing two or more times. You can put successive batches of yarn into the same dyebath, getting lighter colors each time, until the yarn no longer turns blue. Then discard the dyebath. It is safe to pour down the drain. Scrub stains from the pot.
10. After the final airing, wash and rinse the yarn.

Dyeing with Natural, Powdered Indigo in Urine

1. Collect about 4 gallons of urine in a bucket and let it sit for a week or so.
2. Put 1 oz. of natural, powdered indigo in a cloth bag and suspend the bag in the urine.
3. Every day for a month or as long as it takes, rub the bag and put it back in the urine, being careful not to oxidize the urine in the bucket.
4. Gently lower wet wool into the solution and let it sit for up to 24 hours.
5. Remove the wool gently and let it oxidize in the air for about the same length of time that it was soaking in the dye.
6. Wash the wool in soap until the urine smell is gone.

Those who don’t want to use urine can try the baking soda and Thiox directions with indigo cakes. A little more baking soda may be needed. “It’s all about experimentation,” says Thayer.


Thiox is available from Pro Chemical & Dye (prochemical.com), 1-800-2-Buy-Dye (1-800-228-9393). “Call them up and the next day you have the stuff,” said Thayer. “They’ll answer all your questions.”

Salvadoran indigo is available at the MOFGA-El Salvador Sistering booth in the Social and Political Action Area at the Common Ground Fair.

Special treat: Cynthia Thayer will be the keynote speaker at the 2006 Common Ground Country Fair on Friday, Sept. 22nd. She will talk about eating locally grown food in season. “We haven’t bought vegetables in 30 years,” Thayer told The MOF&G, “and have a wide variety of food available to us. The trend to have anything you want available any time you want it relies very heavily on petroleum-based products for shipping.” Many of us believe there is a better way to eat. Come hear Thayer talk about delicious, local food at the Fair.

– Jean English, Copyright 2006

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