Dyeing Wool Yarn Differs from Dyeing Cotton

Common Struggles with Hand-Dyed Cotton Yarn

Dyeing Wool Yarn Differs from Dyeing Cotton

Dyeing wool yarn is one of my favorite pastimes. Experimenting with different plant sources from nature can yield an amazing range of color. Since we raise sheep and fiber goats, most of my experimenting is done with wool, but cotton is another popular fiber. What works on wool, when preparing the fiber for the dye bath will not give you good results when working with cotton cloth or yarn. While some dye sources will leave lasting color on both types of fiber, the road to achieving that color can be very different.

Before you begin to assemble the tools needed for dyeing yarn, know what type of fiber or yarn you have. Wool and animal protein fibers require different procedures than cotton, linen, or other plant-based yarns. It’s important to know the different methods used when dyeing wool yarn or other fibers. Protein fibers include wool, cashmere, mohair, and angora. Silk is an animal protein fiber that is sometimes treated as a plant fiber. The plant fibers include cotton, linen, hemp, bamboo, and others.

The Role of Mordants in Dyeing Process

Mordants are solutions that the fiber is simmered in before it is added to the dye pot. Mordants are an important step to achieving lasting color from the dye process. When dyeing wool yarn, the three most common mordant solutions are white distilled vinegar, alum, or if using plant fiber, aluminum chloride.

Cotton is pre-treated differently. It is important to pre-wash cotton to remove processing oils. Sodium carbonate or washing soda is used as a mordant solution when preparing cotton for the dye pot. In addition, some recipes might suggest adding cream of tartar to the mordant solution for cellulose fibers.

When dyeing fiber, the mordant soaking phase opens up the fibers and prepares them to accept the color from the dye. Some have described the process with the mordant working as a translator, helping the fiber speak the same language as the dye. In any case, the mordant opens up the fibers in the wool or cotton, making them receptive to the dye attaching to the fiber, and sticking around.

Silk is trickier to mordant and sensitive to the time factor. Over-mordanting silk can cause the fibers to be brittle and the natural sheen to break down.

Color Modifiers when Dyeing Wool Yarn or Cotton

Some substances can act as color modifiers after the dye bath or when added at the same time. For example, adding a small amount of iron sulfide to the dye will darken or sadden the color. When adding an iron solution to dye made from purple dead nettle, the dye color is changed from yellow/green to a deep forest green. Hibiscus flowers can yield a deeper shade with the addition of vinegar.

Vinegar can be used as both a mordant and a modifier. The same can be said of soda ash on cotton. Use caution when consulting some older books on natural dye procedures. Some recipes call for the use of toxic or dangerous metals, which we now know can cause serious health consequences. I steer clear of recipes calling for chrome and lead because of the cautions associated with these heavy metals.

Top to bottom: Wool yarn dyed with purple dead nettle, wool dyed with purple commercial dye powder, cotton yarn dyed with madder root, wool yarn dyed with madder root.

Dyes from Nature

Using natural dyes for wool and clothing is perfect for the gardener. If you like to forage in nature, there are many plants that can be gathered from your property or from places you have permission to forage. Barks, nuts, branches from trees, leaves, flowers and stems from weeds and flowering plants, roots of certain plants, and even insects provide a wide-ranging color palette from nature. The goldenrod plant is commonly used to achieve a yellow color on cotton and wool. Madder root provides a deep rusty red shade. And, one of my new favorites, purple dead nettle or stinging nettle gives a deep yellow/green shade. Dyer’s woad is another easy plant for dyeing. It yields a pretty blue dye.

Dyer’s woad.

Other Types of Dye for Dyeing Wool and Cotton

Commercially prepared acid dyes in powder form are another option for creating color on yarn and clothing. Read the directions completely before beginning work with a powder dye. Different techniques are used depending on the type of fiber to be dyed. Also, some dyes are made only for wool or animal protein fiber, and will not be successful on cotton or other plant fibers.


Fiber-reactive dyes are recommended to achieve a lasting color on cotton, linen, bamboo, and other plant fibers. Simply put, the dye contains a reactive group.  The reactive group makes a covalent bond with the fiber polymer and then acts as an integral part of the fiber. These reactive dyes give the best results for dyeing plant fibers. This class of dyes can be used with wool, but it is not the best choice.

Using Madder Root for Dyeing Wool Yarn and Cotton Fabrics

I used madder root dye as an example of the different results achieved from wool yarn and cotton yarn.

Step 1: Prepare the skeins of yarn. Add extra ties at a few points on the skein to prevent tangling. Pre-wash cotton before the mordant phase. Scour the cotton yarn with a pH neutral soap to remove any textile coatings that may have been applied.

Step 2: Mordant both skeins of yarn. Wool should be soaked in a simmering bath of water with 25 grams of alum dissolved in the water for every 100 grams of wool. Simmer for 30 minutes and continue to soak for one hour to several hours.

Soak the cotton yarn in water with washing soda dissolved in the water for the mordant. Heat to simmer and continue to simmer for 30 minutes to one hour. The yarn can continue to soak in the mordant solution while the dye bath is being prepared.  I use 30 grams of washing soda for every 100 grams of cotton yarn.

Getting the Madder Dye Bath Ready

dyeing-wool-yarn dyeing-wool-yarn dyeing-wool-yarn

Step 3: Prepare the dye bath. Each dye substance can have certain recipes. With natural plant dyes, it is fairly safe to vary slightly and experiment. I use 25 grams of dried madder powdered dye for 50 grams of fiber. Remember that each batch will react differently. If a lot of color remains in the dye pot, you can continue to dye fiber with the exhaust bath for a lighter shade of color. The amount of water used should be enough to allow the free movement of the yarn in the dye pot.

Step 4: Simmer the dye bath for at least one hour. Do not boil!  Turn off the heat and leave the yarn and fabric in the dye bath overnight.

Another method used to soak the yarn in the dye bath overnight is a zipper type freezer bag.

Step 5: Rinse the yarn or fabric in cool water until you no longer see color running from the yarn. Wash using a gentle fiber soap. (Some fibers or dyes may suggest further steps such as heating, or steam to set the color.)

Keep in mind that natural dyes are highly variable substances. The soil, seasons, and minerals in the water all contribute to the final color. It is easier to closely recreate colors when using commercial dyes.

Enjoy the process and take good notes as you proceed. You will be amazed at the different colors you can create from both commercial dyes and natural plant dyes when dyeing wool yarn and cotton fabrics.

Do you enjoy dyeing wool yarn and other types of yarn? If so, let us know about your experiences in the comments below.

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