What is a mordant and why do we need it?

A mordant is a mineral salt or metal that is used at the start of the natural dyeing process to prepare the fibre and allow the natural dye to attach to the fabric. The word mordant comes from the Latin word ‘mordere’ which means ‘to bite’.

The type of mordant needed will depend on whether the fibre is cellulose (plant) or protein (animal) based. Taking time to ensure the fabric is correctly and effectively prepared before dyeing is essential to ensure successful results when it comes to colouring the fabric. Mordanting also improves light and wash-fastness, which will give the dyed fibres colour more longevity and can produce brighter, clearer tones.

There are a number of different effective mordants and the quantities and techniques can vary between dyers. The most common mordants are; for cellulose fibres: Aluminium Acetate and for protein fibres: Aluminium Sulfate. It’s also worth noting that the PH of water used and mineral components in water from different sources can also affect your processes, so it is always good experiment and find out what works best for you.

A general guide to mordants:

Vegetable fibres - 20% alum and 6% washing soda per 100g dry fibre.

Animal fibres - 8% alum and 7% cream of tartar per 100g dry fibre.

Always pre soak your fibre for at least 24 hours prior to mordanting and be sure that there is enough of the mordanting solution to cover your fibre well. Allow the fabric to soak in the mordant for 24 hours - moving the fabric at times to ensure even results.

Happy dyeing!

Zowie x