Mordant

Biting; caustic; sarcastic; keen; severe.

Serving to fix colors.

Any corroding substance used in etching.

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.

Any sticky matter by which the gold leaf is made to adhere.

To subject to the action of, or imbue with, a mordant; as, to mordant goods for dyeing.

harshly ironic or sinister; "black humor"; "a grim joke"; "grim laughter"; "fun ranging from slapstick clowning … to savage mordant wit"