Frottage
Technique principally used by M. Ernst and other surrealists in a series of drawings. The paper, on which the project will become, is placed on a more or less rough or textured surface and is rubbed (FR, frotter = friction) by pencil, charcoal or anything else until the elements of the lower surface be reflected. The result is an event of so-called "random object" and a source of activation of the artist’s imagination.