Potassium Aluminium Sulphate (Alum)

Potassium aluminium sulphate, commonly known as Alum is one of a group of chemicals known as a mordant. A mordant acts like a bridge between fibre and dye and fixes the dye to the fibre. It deepens and enriches the colours for most dyes and improves light and washfastness.  Alum is the safest mordant to use  but I recommend that  gloves  are worn to protect the hands when using a mordant bath.

. A standard recipe for wool and silk is 10% of the Weight of Fibres (WoF) in Alum and 8% WoF Cream of Tartar, which acts as an assistant. Mordant baths can be reused.  Just add half as much again of Alum and cream of tartar.

For cotton and other cellulose fibres Alum is part of a two or three day process  combined with washing soda. For more information on how to use Alum read my book Colours of the Earth Natural Dye recipes now available as digital download.

Spent mordant baths can be disposed of down the sink or around acid loving plants such as hydrangeas .