A transfer technique in which an artist spreads gouache on a sheet of paper, lays another sheet on top of it, presses on the second sheet in places, then lifts it off.  Decalcomania can produces effects suggesting organic forms, clouds, or variegated geological deposits. The Surrealists adopted the technique to create imagery by chance rather than through conscious control.

Marcel Jean. Untitled. Decalcomania with gouache additions on paper. 1936. Museum of Modern Art, New York.