One of Duchamp's close friends and a member of the New York Dada scene, the American photographer and painter Man Ray (1890-1976) was also one of Duchamp's collaborators. His photograph Dust Breeding (Duchamp's Large Glass with Dust Motes) from 1920 is a document of The Large Glass after it had collected a year's worth of dust while Duchamp was in New York. The photograph was taken with a two-hour-long exposure that beautifully captures the complex texture and diversity of materials that lay atop the glass surface. Dust Breeding marks a pivotal phase in the development of Duchamp's masterpiece. After the photograph was taken, Duchamp wiped The Large Glass almost entirely clean, leaving a section of the cones covered with dust, which he permanently affixed to the glass plate with a diluted cement.