The medium is as unimportant as I myself. Essential is only the forming... I take any material whatsoever if the picture demands it. When I adjust materials of different kinds to one another, I have taken a step in advance of mere oil painting, for in addition to playing off color against color, line against line, form against form etc., I play off material against material, wood against sack clothes.

Schwitters (1921) in: Abstract Art, Anna Moszynska, Thames and Hudson, London 1990, p. 68-69.