It was during a fifteen-year period of intense experimentation beginning in the mid-1940s that Louise Nevelson evolved her sculptural wood collages, assembled from found scraps, including parts of furniture, pieces of wooden crates or barrels, and architectural remnants like stair railings or moldings. Generally rectangular, very large, and painted black, they resemble gigantic paintings. Concerning Nevelson's Sky Cathedral (1958), the Museum of Modern Art catalogue states, "As a rectangular plane to be viewed from the front, Sky Cathedral has the pictorial quality of a painting..."[13][14] Yet such pieces also present themselves as massive walls or monoliths, which can sometimes be viewed from either side, or even looked through.