2. Tan the Cotton With 10% Sumac Extract.

Fill a dyepot with just enough warm water for your cotton to move around freely. The amount of tannin the fiber absorbs will depend on the concentration of tannin in the water, so you do not want to dilute the tannin bath with any more water than is necessary.

Measure out 10% weight-of-fabric (WOF) of Sumac Extract. Put it in a disposable cup and add a little hot water; mix well to make a thick slurry. This is the best way to break up any clumps, which could cause splotches on your fiber later on in the dyeing process.

Add the Sumac Extract slurry to the water in the dye pot and mix well until fully dissolved. Add your scoured (clean) cotton fibers and raise the heat to 190F-200F (just below a boil). As soon as the tannin bath hits 200F, remove the pot from the heat, cover, and allow to cool to room temperature. The cotton should steep for at least 3 hours (for thin material like t-shirts) or 6 hours (for thick material like broadcloth). If time permits, steep overnight.

[Note that cotton does not actually absorb much tannin at or near the boiling point; most of the absorption happens gradually as it cools between 120F and 90F. Simply boiling cotton in a tannin bath will yield disappointing results. However, we recommend initially heating the bath to 200F to help drive any air out of the cotton and help force water into the fibers.]

3. Gently Wring the Cotton and Let It Dry

After the cotton has fully steeped in the tannin bath and cooled to room temperature, gently remove it and let the excess liquid drip back in the pot. Do not rinse it. At this point the tannin is not chemically bonded to the cotton, and rinsing can easily wash the tannins right back out. Wearing rubber gloves, you may gently squeeze out excess water. However, we recommend squeezing out only as much as is absolutely necessary so that the cotton does not drip all over everything while you hang it up to dry. The more of the tannin liquid you leave in the cotton, the more mordant and dye it will absorb later.

Hang the cotton up to dry, preferably on a clothesline in direct sunlight. Alternately, you can hang it in front of a fan or gentle heat source to dry it faster (on cold, rainy days, we will sometimes hang the cotton in front of a gas fireplace to dry, but be careful not to place it so close that it becomes a fire hazard). Drying the cotton will take some time, but there is simply no getting around this step: letting it dry is what initially attaches the tannin to the cotton. If you try to mordant the cotton immediately after removing it from the tannin bath, while it is still wet, much of the tannin will wash out before it can bond to the alum, and the end results will be disappointing.

4. Mordant with 20% Alum and 5% Soda Ash

Fill your dye pot with enough lukewarm water for your cotton to move around freely. Measure out 20% weight-of-fabric of alum powder and add it to the pot. Mix well until fully dissolved. Measure out 5% weight-of-fabric of soda ash into a disposable cup and fill the cup mostly full with cold water from the tap. Mix well to break up any clumps, then let it sit for five minutes to settle. When it has settled, pour it into the mordant bath, mixing well with a metal spoon or tongs as your pour it in.

[The addition of 5% soda ash will neutralize the acidity of the mordant bath and cause some of the alum to precipitate out of solution. If stirred, the alum will dissolve and the mordant bath will turn clear or milky. If you let the water settle, little flecks of alum will start to precipitate out again. The 19th-century dyeing manuals all agree that the correct proportion of alum to soda ash is 4:1, so if you use more or less alum, adjust the soda ash accordingly.]

Heat the mordant bath to 130F, stirring regularly. As soon as the temperature hits 130F, put the dry cotton in and turn off the heat. If you listen closely sometimes you will hear a brief fizzing sound as the cotton enters the mordant bath; this is a sign the tannin is reacting with the alum.

Using tongs or a metal spoon, gently work the cotton in the mordant bath for 3 minutes (for thin material like t-shirts) or 5 minutes (for thick material like broadcloth). Turn it over a few times, stir it a few times, and make sure any folds or creases get evenly soaked in the mordant. After no more than 5 minutes, remove the cotton. When it is cool enough to handle, squeeze out just as much liquid as is absolutely necessary so the cotton does not drip everywhere, and hang up to dry. When it finishes drying a second time, it should have a distinctly yellow cast from all the absorbed alum.

Note that if you would like to add a tie-dye pattern to your cotton, make the ties now, after the cotton has dried from the mordanting bath.

1. Prepare a Dyebath Using 12% Cochineal

[Note - You can build the dyebath at any convenient time while tanning and mordanting the cotton, which takes a day or two to complete. Adding cream of tartar helps extract the carminic acid and hold it in solution.]

Fill a dye pot 1/2 full with hot water. Adjust the PH to 5 using Cream of Tartar; if you don’t have PH strips, add 1 tsp Cream of Tartar and mix well until dissolved. Add 12% weight-of-fabric of ground or whole cochineal. To get the correct amount, multiply the dry weight of your cotton by 0.12. Bring to a gentle boil, cover, and maintain the heat for 1 hour (2 hours if using whole cochineal). Remove from heat and let cool to room temperature. If time permits, let steep overnight.

Strain the dyebath through cheesecloth or (if using whole cochineal) a fine mesh strainer. Filter it into a holding container, like a plastic bucket or another pot. Return the strained cochineal to the dye pot, fill it 1/2 full with warm water, and boil for another hour to get all the color out. Filter this second extraction and combine it with the first one. Carefully dispose of the spent cochineal (it will still stain anything it touches red), rinse any solid bits of cochineal out of your dye pot, and return the combined extraction liquid to it. This will be the dyebath.

5. Boil the Cotton for 1 Hour

Raise the heat of your cochineal dyebath (see Step 1) to 170F-180F and gently place the dried cotton in. You want the bath to be hot when the mordanted fiber is placed in it, so that the carminic acid immediately bonds to the alum dried in the cotton. Bring to a boil, cover, and maintain at a gentle boil for 1 hour.

[Optional] - If you want to shift the color to purple, you can “sadden” the dyebath with iron during the last 5 minutes of dyeing. Carefully lift the cotton out with metal tongs, add 2% weight-of-fabric iron powder, mix well, and then put the cotton back in for the last 5 minutes.

After one hour, remove the pot from the heat and allow the cotton to cool to room temperature. If all has gone well, your cotton should now be a beautiful shade of crimson or magenta (or purple, if you added iron). Note that after rinsing and drying, the cotton will be a few shades lighter than it looks now.

6. Dry, Rinse, and Dry

Wearing rubber gloves, remove the cooled cotton from the dyebath and gently wring out the excess liquid so it does not drip. Hang the cotton up to dry.

When the cotton is completely dry, it is ready for rinsing and washing. Make a bath with hot water and a few drops of PH neutral soap like Synthrapol. Cochineal is very sensitive to PH, so you may wish to adjust the PH of the rinsing bath to match the dyebath so it does not shift the color. Add some white vinegar along with the Synthrapol to acidify the rinsing bath, if desired. Wearing rubber gloves, work the cotton well in the hot water, then wring out. Repeat until the water runs clear: you may need to repeat the process once or twice with fresh rinsing baths.

When finished, hang up to dry somewhere out of direct sunlight.

Fig. 5.1. If the tanning and mordanting were successful, the cotton will start to take color in just a few minutes.

Fig. 5.2. Boil the cotton for one hour to fix the color; cotton responds best to high temperatures.

Fig. 6.1. After drying, rinse with PH-neutral soap until the water runs clear.

Fig. 2.1. The goal of the tannin bath is to soak as much dissolved Sumac Extract into the cotton fibers as possible.

Fig. 3.1. The cotton should be absolutely dry before you proceed to mordanting.

Fig. 4.1. The addition of 5% soda ash will cause some alum to precipitate and make the mordant bath look cloudy.

Fig. 4.2. This brand new white cotton t-shirt now looks yellowish because it holds so much tannin and alum.

Fig. 6.2. Proper tanning and mordanting is the key to getting beautiful reds and purples on cotton.