Frottage

In art, frottage (from the French frotter, to rub) is a surrealist and "automatic" method of creative production developed by Max Ernst in which one takes a pencil or other drawing tool and makes a "rubbing" over a textured surface. The drawing can either be left as is or used as the basis for further refinement. While superficially similar to brass rubbing, frottage differs in being aleatory in nature.