Mordant
A mordant is a substance, usually a metal salt such as alum, that fixes a dye to fibre and can change its colour.
Many natural dyes will not bond to fibre on their own. A mordant, from the French mordre, to bite, is applied before or with the dye to make the colour fast. Alum is the classic mordant; iron, tin and copper salts darken or brighten colours.
Why does it matter for printed textiles?
Printers learned to print the mordant rather than the dye: when the cloth was dyed in madder, only the mordanted areas took colour, and different mordants gave different shades from a single dye bath. This was the basis of Indian chintz.
Sources
- Mordant (AAT 300015299). Getty Art & Architecture Thesaurus
- Mordant (Q5857145). Wikidata
See also
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