Chops, which were a
forerunner to the invention of printing,
are engraved by hand, pressed into a red
ink paste made from Cinnabar and stamped
onto a painting or document. Chops are generally
made of jade into which an
elaborate sculpture is often carved.
Chop marks contribute to the
visual appeal of the painting but chop
marks themselves also constitute an
independent category in fine arts. Throughout
most of the Far East
classes devoted to this craft
are held in colleges and university
departments.