MORDANT (2)

Mor″dant, n. [] 1. 1. Any corroding substance used in etching.
2. 2. (Dyeing & Calico Printing) Any substance, as alum or copperas, which, having a twofold attraction for organic fibers and coloring matter, serves as a bond of union, and thus gives fixity to, or bites in, the dyes.
3. 3. (Gilding) Any sticky matter by which the gold leaf is made to adhere.