Potassium aluminium sulphate, for mordanting.
Use 8g per 100g dry weight of goods with 7g Cream of Tartar, available from your local supermarket (Dr Oetker or Supercook).
For cold mordanting, use 10g per 100g dry weight of goods, plus 5g Cream of Tartar. Dissolve in hot water then add the wetted goods and leave overnight.
