Introduction: How to Mordant Protein Fibers With Alum

Mordanting is an important step prior to dyeing yarn using natural dyes, as it makes the colors lighfast and washfast. It is used primarily with protein fibers (wool, alpaca, silk, etc.)

There are many different mordants that have different purposes, and one of the most easy to use and easy to find is Alum (potassium aluminium sulfate). You can buy it in the baking seciton of most grocery store, or on the Internet.


Step 1: Equipment + Tools

  • Protein yarn or fabric
  • Alum
  • Kitchen Scale
  • Dishwashing plastic gloves
  • Mason jar (or any equivalent size glass container)
  • Small glass bowl
  • Stainless steel pot (or unchipped enamel)
  • Wooden stick or spoom

Step 2: Preparing the Mordant Bath

Alum is generally used to a 15% concentration.

For example
If you are mordanting 100gr of wool, you will use 15g of Alum to mordant it. If you are mordanting 200gr of wool, you will use 30g of Alum to mordant it. ( And so on... )

  • Turn on the scale
  • Put the small bowl on it, tare it ( or calculate the difference between empty bowl and bowl with alum)
  • Weight the alum until you get the required amount.
  • Fill your mason jar with boiling water.
  • Pour the Alum in the water, and stir with the wooden spoon until Alum is fully dissolved.
  • Empty this Alum solution in your stainless steel pot and add cool water (Enough so that it will cover the yarn or fabric you wish to mordant)

Step 3: Mordanting

  • Put clean & yarn or fabric in the pot. Add water if needed.
  • Turn on the stove to medium. Bring to a simmer and hold there for an hour.
  • Leave for a minimum of 30 minutes and up to 1 hour, stirring occasionally to insure even absorbtion of mordant in the yarn/fabric. Do not boil. When you stir do it very slowly, as heat and agitatiuon causes felting of the wool (If silk to not go above 80 celcius degrees as it damages the fibers.)
  • When finished, turn off the stove and let cool down and hand your yarn or fabric to dry OR You can also use them right away in a dye pot.