This caution was overcome by the discovery of such techniques as frottage and decalcomania.
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He also explored with the technique of decalcomania which involves pressing paint between two surfaces.
From the en.wikipedia.org
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Decal: either a design that is fixed to some surface or a paper bearing the design which is to be transferred to the surface
The art of transfering designs from specially prepared paper to a wood or glass or metal surface
Decalcomania, from the French du00E9calcomanie, is a decorative technique by which engravings and prints may be transferred to pottery or other materials. Today the shortened version is "Decal".
The process of transferring decorative designs onto surfaces using decals
Press sheet of paper onto paint covered surface, peeling sheet off