Crystoleums (photographs)

Distinctive photographs made from a hand-colored positive image process used from the 1880s through 1910, intended to give the appearance of painting on glass. An albumen paper print is adhered to a curved piece of glass and sanded from the back to the emulsion layer. A layer of oil is applied to render it translucent, and detailed color is applied to the back. When dry, a second layer of curved glass is added, and painted with broad fields of color. A layer of white material was applied behind this, and everything bound together. The glass, solutions, and adhesives were available commercially until World War I. The process was based on 18th-century hand-colored engravings known as mezzotint paintings.