How to Mordant

Our How To guides are intended to make the dye process easy, from How To Mordant to scouring your fibers to dyeing with an assortment of dyes. You can find other How To guides here.


Mordanting is the most important process of preparing fibers to accept color. This is not an optional step but there are many mordant variations, and indigo as a vat dye does not require a mordant. Using a mordant helps to ensure the most durable and long-lasting colors.

(Check out our recent Q & A: Round Up of Mordanting + Scouring 101 here.)

The technique is simple (for animal fibers): measure the mordant, dissolve in water, and add to a dye pot or bucket or tub filled with water. Simmer the fibers for a period of time, then remove and proceed to the dye bath. Although many substances have been used in the past for mordanting, we prefer aluminum potassium sulfate as a mordant for animal or protein fibers. See our detailed instructions for mordanting animal fibers here.

Plant fibers have a recommended second step. We prefer aluminum acetate for cellulose (cotton, linen, bamboo, etc.) fibers, as well as for protein/cellulose blends, like wool/hemp, silk/bamboo and silk/cotton. See our detailed instructions for mordanting plant fibers here.

Which mordant to use?

For basic mordanting, refer to this table. Once you are comfortable with these techniques, you may explore other mordant options, including the use of iron, tannin and alum, tannin alone and compare results.

Fiber contentRecommended MordantOther Mordant Options
Wool, alpaca, and other animal fibers Aluminum Potassium Sulfate with optional Cream of Tartar

Aluminum Sulfate
SilkAluminum Potassium Sulfate

Aluminum Sulfate
Aluminum Acetate with wheat bran afterbath

Cotton, linen, Tencel, bamboo and other plant fibersAluminum Acetate with wheat bran or with calcium carbonate afterbathTannin andAluminum Sulfate