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Harvesting Color: The Mordanting Process

Learn about the mordanting process and more about creating beautiful, natural fiber dyes.

(Harvesting Color, Page 2 of 3)

  © Rhoda Peacher

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As mentioned before, dyeing (applying color to fibrous materials) is a different process than painting with pigments. In painting, pigment needs to be applied only to a top surface. Coloring with dye requires impregnation and absorption of the color on an integral level. The color actually has to be absorbed into and bonded with the fibers themselves, which we know as the term “colorfast.” Many dyes do not adhere to the fibers, despite the initial appearance, and must have a special bond applied to assure a lasting effect. This is accomplished by using a fixative, or mordant, whose name is from the Latin root “mordere,” meaning “to bite.”

While stains are the bane of laundry-doers everywhere, with dyeing, the colors you want to stay can often rinse out. Because of this, it becomes important to  mordant the fibers you plan to dye prior to immersing them in the dyebath. 
To mordant the fiber means to soak it in a bath of water that has been treated with a special metallic  compound. While a few dyes will attach to fiber without a mordant, for most it will help hold the color in the fiber, making it less susceptible to fading (i.e., more colorfast) and making the colors brighter. Most commonly, solutions of aluminum, tin, iron, copper, alum or chrome are used. Different mordants will yield different shades from the same dye on the same fiber. You can create an endless variety of hues when using different mordants and different fibers with just one dye material.

Alum is the compound most often used with animal fibers (wool and silk). It should be used in conjunction with cream of tartar, which chemically increases the amount of alum absorbed by the fiber. This will provide maximum color absorption and will help to make sure there are no metallic residues left in the mordant  solution so it can be safely disposed of down the drain when you’re finished.

The Mordanting Process
  1. Weigh the dry yarn, making note of the weight. Wind yarn into a loosely coiled skein, securing with white string or thread in four or five places so it doesn’t unwind. Be careful not to tie the strings too tightly or you may end up with a tie-dyed effect when the process is done. Soak your skein in cool, clear water for an hour or until thoroughly saturated. Squeeze out the excess water from the fiber before putting it into the mordant bath.

  2. Prepare the mordant bath. As mentioned, different mordants will give different finishes to the colors. Alum is readily available at grocery stores, being a common ingredient in home-pickling, and it yields bright, clear colors. For an alum mordant, use 13⁄4 teaspoon alum and 11⁄2 teaspoon of cream of tartar for every 4 ounces of fiber you plan to dye. Allow at least 4 gallons of water per each pound of fiber. Dissolve the cream of tartar in 1 cup of boiling water, stir well and add this liquid to a large kettle of mordant water. Do the same with the alum, dissolving it well before adding it to the cool water in the kettle.  Stir well.

  3. Put the wet yarn into the cool mordant water and turn on the stove. Gently raise heat to a simmer and cook for an hour (do not boil wool or it will shrink and bond together), stirring periodically to assure even saturation. Make sure all the fiber matter is submerged beneath the liquid after each stir. After one hour, turn off the heat and leave the fiber in the pot overnight. 

  4. Once the yarn is mordanted, it’s ready to be dyed. Wring the skein firmly by hand, squeezing out as much liquid as possible. At this point, you can hang it up to dry and dye it at your convenience or you can leave it moist and move right into the dyeing process.

The Do's and Don'ts of Dyeing?

  • Make certain that all fibers are thoroughly cleaned of grease, oils and dirt before  mordanting and dyeing. Mordants and  colors will take unevenly if there is any residue remaining on them.

  • Use only stainless steel or non-reactive cookware to do the dyeing, otherwise results may be affected. On the other hand, experiment and play! Iron and copper can act as mordants and will render a different color from others, so a cast-iron or copper kettle can give you a different result when the yarn is mordanted in them.

  • Be aware that the liquids and fibers are hot when they’re rinsed out. Use hot mitts to handle the pans and be cautious of hot splashes when pouring out materials. Be aware that unintended dyeing (aka staining) may occur from splashes on surrounding areas and material.

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Harvesting Color: The Mordanting Process

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Reader Comments
This is a very interesting article. Thanks for the information.
Tracy, Burns, OR
Posted: 6/25/2009 11:44:20 AM
Wow, how enlightening. This isn't anything like what I thought it would be. Thank you for such an informative article!
Claudette, Farmington, MO
Posted: 5/8/2009 5:54:26 AM
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