Max Ernst developed frottage by rubbing textured surfaces through sheets of paper.
Ernst began exploring the method in 1925, after noticing suggestive patterns in the grain of a wooden floor. He placed paper over a textured surface and rubbed it with a pencil, allowing accidental forms to prompt imaginative interpretations. The resulting images often resemble forests, creatures or mysterious landscapes.
Frottage gave Surrealist artists a way to reduce deliberate control while still transforming ordinary materials into evocative imagery. Ernst published a group of such works in his 1926 book Histoire naturelle, which helped establish the technique.
Frottage is sometimes confused with decalcomania, another Surrealist process based on transferring paint between surfaces. Ernst also developed grattage, in which painted surfaces were scraped to expose textures beneath them.