CD 40 is composed of small cubes of upcycled cardboard, blackened and set densely across a field of 130 x 100 cm. The blocks vary in height and angle, producing a surface that recalls charcoal, basalt or a burnt landscape. Guy Leclef has spoken of order within chaos as a recurring concern, and here the grid of cubes is both regular and unstable. The black tone absorbs light, so that the relief is read mainly through its shadows and edges. Similar blackened cardboard cubes appear on the cover of the artist's monograph Paperworld.