Alum mordant for use to colour protein fibres (wool, hair and silks) with natural dyes, and in combination with tannin for cellulose fibres. Synonyms: Potash Alum.
Alum mordant links chemically with the fibre and creates attachment points which bond with the colourant from natural dyes creating light and wash fast colours. It anchors the colour obtained from dye plants (depending on the plant used) and can be used for yellows, lovat, orange, red, and purple. We encourage experimentation and recommend careful record keeping to help reproduce colours in future dye sessions.
It helps to soak the wool in warm water and squeeze out excess before adding to the mordant bath. For every 250g of the dry wool or silk, use 50g of alum mordant in 5 litres of water. Add 10g of Cream of Tartar to help soften the fibre and brighten the colours. Gradually heat the mordant bath to around 80°C for 30 minutes and allow to cool slowly. Remove the wool and squeeze to remove excess liquor.
After mordanting, the wool can be simmered with any of the natural dyes. It may help to place the dyestuff in a mesh bag before adding to the dyebath. Simmer for approximately 30 minutes and turn off the heat. Allow the wool to cool slowly in the dyebath before removing it. Gently rinse out excess dye in clean water.
Alum is also used to treat fabrics and paper prior to marbling to help paint transfer.
Alum mordant has also become popular for use in Botanical Printing, also known as ECO printing. This experimental technique is effective on cotton and linen fabrics, as well as wool fabrics including felt, silk fabric and cotton paper. The material is first soaked in a 10% solution of alum mordant (100g to 1 litre) or alum and iron solution and leaves and petals are placed onto it while it is still damp. The fabric is folded, rolled up and parcelled in cling film or aluminium foil before being steamed to extract the colour. Likewise, leaves and petals can be sandwiched between sheets of mordanted paper and steamed. See here for our steaming instructions which are used to heat-set silk dyes.
Please note that there are hazards associated with the use of this product. Follow the advice on the label at all times.
