Iron Aftermordant or Modifier Recipe

An iron aftermordant or modifier can help darken natural plant dyes for a deeper color.

Dyed Animal Fibers

An iron aftermordant can be added directly to the dye bath after you’ve removed it from the heat and before you’ve added the fiber to the dye bath.

Photo by Fotolia/Maksim Shebeko

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Home dyeing can be a gamble if you are new to the idea, but even if you are experienced in the art, knowing the different reactions given by plant based fibers and animal fibers can be crucial to proper dye absorption. Using the Handbook of Natural Plant Dyes (Timber Press, 2010) Sasha Duerr walks you through using mordants and natural dyes in perfect harmony. Use this Iron Aftermordant Recipe to give your natural plant dyes a muted, darker look.

Iron Aftermordant or Modifier Recipe

Iron is a good aftermordant for darkening or modifying dye color. An iron modifier can be added directly to the dye bath after you’ve removed it from the heat and before you’ve added the fiber to the dye bath. Measure the dry weight of your fiber before soaking.

4 ounces (113 g) fiber
2 percent (1/2 teaspoon) iron powder to weight of fiber

Soak the fiber in water for at least 1 hour.

Prepare the dye bath you wish to use, according to any recipe in this book.

Remove the fiber from the soak water, and add it to the dye bath.

Dye the fiber according to the recipe you have chosen. Remove the dye pot from the heat, and let the fiber cool. Remove fiber from the dye bath and hang the fiber to reach room temperature.

Put the iron powder in a cup, add some hot water, and stir to dissolve. To the dye bath you’ve just used, add the iron solution and stir. The dye bath may be cool at this point, and it’s better to have the bath well under the boiling point to avoid breathing vapors. You may notice an immediate change of color for dyes that are especially sensitive to iron.

Place your dyed fiber back into the dye-iron solution. Stir gently so the fiber achieves even coloring. Let the fiber soak in the dye bath for at least 15 to 20 minutes.

Remove the fiber, wash well with pH-neutral soap, and rinse thoroughly. Hang to dry.

Use mordants and aftermordants for your home dyeing projects. Read Using Mordants With Natural Plant Dyes for more recipes and tips from Sasha Duerr.


This excerpt has been reprinted with permission from The Handbook of Natural Plant Dyes: Personalize Your Craft With Organic Colors From Acorns, Blackberries, Coffee and Other Everyday Ingredients, published by Timber Press, 2010.