How to Make an Alum Mordant: how_alum_mordant

Natural dyeing is usually a 2 step process. The yarn or fibre must be soaked in a mordant,
that prepares the fibre to absorb the natural dye substance.

alum mordant

Difficulty Level:


Time Required:

90 minutes

Here’s How:

  1. Use clean, scoured wool or yarn.
  2. Fill a large pot with clean water and heat.
  3. Weigh the yarn or clean, dry fleece.
  4. Using 10% Alum (potassium aluminum sulfate) to weight of fibre, mix the Alum into the hot
  5. Using 5% Tartaric Acid to weight of fibre, add the Tartaric acid to the hot water
  6. Rinse the wool so that it is damp.
  7. Add the wool or skeins of yarn into the hot Alum mixture.
  8. Make sure that the wool is all covered by the water, if not, add more water to the
  9. Simmer the mordant mixture for x-about an hour at 90 degrees Celsius.
  10. Remove the yarns from the Alum mixture.
  11. The Alum mixture can be reused by adding 1/2 the amount of Alum and Tartaric


  1. If dyeing skeins of yarn, make sure that the skeins are tied securely, but loosely in at
    least 3 places, to avoid tangling.
  2. The mordanted yarns can be dyed immediately, or dried and stored for later natural
  3. The alum/tartaric acid mixture is suitable for wools, silks and other protein

How To Mordant Cotton and Linen
How To Make a Tin Mordant
How To Wash Fleece
Natural Dyes and Mordant Recipes
MSDS – Aluminum Potassium Sulfate

Where to Buy Alum Mordant

Dyeing Crafts
Wild Colours
Maiwa Handprints

Natural Dye Books

Natural Color: Vibrant Plant Dye Projects for Your Home and Wardrobe
Wild Color, Revised and Updated Edition: The Complete Guide to Making and Using Natural Dyes
Eco Colour: Botanical Dyes for Beautiful Textiles
The Art and Craft of Natural Dyeing: Traditional Recipes for Modern Use