This a continuation of my mordant post last Friday.

There are lots of mordants out there. Mordants cause dyes to be more lightfast, or to fade less. They act as a bridge to hold the dye to the fabric. Different types of fabrics use different mordants. Sometimes in different combinations and order. Here are some of the more common ones, and some not so common ones, I have used.

  • Dyer’s alum (potassium aluminum sulphate) – wool and silk
  • alum (aluminum sulphate) – wool
  • copper (copper sulphate) – wool
  • iron (an old rusted steel horseshoe or spike) – wool and silk
  • black tea – wool, silk, and cotton
  • Staghorn sumac leaves (used with Dyer’s alum and cream of tartar on cotton) – cotton
  • onion skins (a mild mordant that I use with other mordants) – wool, silk, and cotton

Modifiers can be added to change or alter colours or pH of the dyebath too. It is usually added after the dye. These help to ‘set’ the dye. Some of these are listed below.

  • Vinegar
  • citric acid
  • baking soda
  • washing soda
  • cream of tartar

The biggest concern with mordants is always safety. Mordants are needed for natural dyeing, but you can have too much of a good thing. I won’t use the iron powders sold because they are too dangerous. Likewise with copper sulphate. I used it once and will not do so again. Nor tin, nor chrome. Alum is a much safer alternative.

The key to successful and safe mordant use is to exhaust the mordant bath before disposing of it. That means saving it and using it over and over again until it no longer works. Checking the pH with a pH strip to make sure it’s neutral before disposal is a good idea too.

Mordant and modifier samples on wool fabric.

The above is before dyeing. After dyeing you may get results like below…

You can see the difference a mordant or modifier makes!

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