Mordant:
A mordant or dye fixative is a substance used to set (i.e. bind) dyes on fabrics by forming a coordination complex with the dye, which then attaches to the fabric (or tissue).[1] It may be used for dyeing fabrics or for intensifying stains in cell or tissue preparations. As applied to textiles, mordants are mainly of historical interest because the use of mordant dyes was largely displaced by directs. [Wikipedia]
Encountered, as in my previous entry, in Jack Vance’s The Blue World. Passage omitted.
