Influenced by Surrealism’s emphasis on unconscious or automatic procedures for art-making, Max Ernst developed frottage, a drawing technique in which canvas or paper is laid over a textured material and rubbed with a pencil to create a spontaneous, irregular surface. Ernst's Papillons and La forêt (2002.15.21) both employ grattage, a variation on this rubbing technique that employs oil paint. In Papillons, after placing the canvas over a rough surface and covering it with multiple layers of paint, Ernst scraped away the outermost layers to reveal an arrangement of butterfly forms. La forêt is part of a series of forest images from the late 1920s, most of which include a solar disc and a bird trapped among branches. The dark forest was a popular image in nineteenth-century German Romantic art, and it was adopted by the Surrealists as a metaphor for the imagination.