Alum mordant is used to colour protein based fibres such as wool and silk. It can also be used for cellulose fibres such as cotton but for better results we recommend Aluminium Acetate mordant.
Alum helps improve light and wash fastness of dyes by enhancing the chemical bonding properties to the fibres resulting in brighter colouration.
Before dyeing ensure the fibre is first washed in warm water using a gentle wool wash, wring out excess water and then add to the Alum mordant bath at approximately 50g per 5 lites of water. The addition of Cream of Tartar is recommended at this stage to help soften the fibre and brighten natural colours. Heat the mordant bath to 80 degrees and simmer for about 40 minutes and cool slowly to avoid felting the fibre. Remove the fibre from the mordant bath and gently squeeze out any remaining liquid.
After the mordanting step, the wool fibre can be gently heated and simmered for apprximately 30 minutes in the dye bath with your selected natural dye. Again allow the fibre to gently cool in the dyebath before rinsing in clean water.
After dyeing, use a dye assist to modify the colours if required.