Natural Dyeing: Mordants

Mordant, from the French "mordre" to bite. If you're going to use natural dyes, you need to pre-treat your fabric or the color won't hold. We do this using two classes of mordants: metallic and tannin. Mordants cause the color to 'bite' the fabric. Your mordants must be dissolved in warm water before being added to the fabric.

Basic Mordanting Points to Learn

Mordant Effects

To much mordant can cause:

Alum - harsh and sticky
Chrome - color streaky
Tin - harsh and brittle feeling

  • • All mordants should be pre-dissolved and added separately to water bath.
  • • Fabric must always be removed before adding additional mordants.
  • Don't Over Crowd the Bath! Your fabric will end up blotchy when dyeing if you do.
  • • Avoid sudden changes in the mordant bath; steadily increase the temperature.
  • • Slowly add additional water to the bath, as the boiling causes evaporation.
  • • Dispose of any remaining solution safely. Do not use it to water your garden or in your septic tank.
  • • These are still chemicals and care must be taken. A good idea would be to contact your local city health or sanitation department to see what they recommend for disposal.

Types and Methods

Alum: Available in most grocery stores and very safe to use; it's normal to add cream of tartar to produce brighter, cleaner colors. Dissolve the Alum (about 3 oz. per pound of fabric or yarn and 1 oz. cream of tartar) separately in warm water. Pour into a water bath of 4 gallons of water, heated to 160°. Add your fabric being careful not to crowd. Bring to a slow boil in about 30 minutes and then hold at that level of boil for 45 minutes. Your fabric will take a better dye if you allow it to cool in the bath. You can use it immediately, or let it dry. Chemical name: potassium aluminum sulfate.

Chrome: This gives wonderful deep, rich colors. You have to be more careful with it, then the alum, to avoid uneven coloring later on. Adding cream of tartar will help brighten the colors even more. Use 1/2 oz. of chrome with 4 gallons of water, to 1 pound of fabric or yarn. Heat the water to 160°, and remember to pre-dissolve the chrome in warm water first. Put your wet, washed fabric in the bath and simmer for 30 minutes. Remove the fabric, add 1/2 oz of cream of tartar (pre-dissolved) stir thoroughly, replace the fabric and simmer for 1 hour. Be careful to keep the fabric totally under the water in the bath, or when you do dye your fabric it will streak. Wash the fabric after mordanting in the chrome and allow it to dry slowly, before dyeing. If you're going to be dyeing the fabric lighter colors, you can use a bit less chrome. Too much will result in a harsher feel to the fabric. Chemical name: potassium bichromate.

Tin: The most difficult of all the mordants metallics to use. Too much will destroy your fabric or yarn. Its greatest use is as an aid to other mordants, with bright, crisp yellows and reds resulting. As an actual mordant, use 1/2 oz. tin, with 2 oz. cream of tartar and 3/4 oz. oxalic acid - to one pound fabric or yarn in 4 gallons of water. Heat the water to 140°, put in the wet, washed fabric and raise the temperature of the bath to 190°. Hold at that level for 1 hour. Do Not Boil. Chemical name: stannous chloride, tin crystals. Oxalic acid is Oxalic wood sorrel, a bleaching or cleaning agent - very strong acid.