Mordant

(Glossary Term)

A chemical substance, which when combined with a dye, causes the colour substance to bind to the fabric. Mordants are essential for most dyes used on cotton and other cellulose fibers (with the notable exception of indigo) since dyes bind poorly to cellulose on their own. This fact can be exploited to make patterns on textiles by painting or printing the mordant onto the surface before dyeing.