The crystoleum, from "crystal" + "oleum" (oil), process was a method of applying colour to an

albumen print The albumen print, also called albumen silver print, was published in January 1847 by Louis Désiré Blanquart-Evrard, and was the first commercially exploitable method of producing a photographic print on a paper base from a negative. It us ...

, popular from .Ritzenthaler. (2006). p. 39. An

was pasted face down to the inside of a concave piece of glass. Once the adhesive (usually

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...

paste or

gelatin Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...

) was dry, the paper backing of the print was rubbed away, leaving only the transparent emulsion on the glass. The image was then coloured by hand, using

oil paints Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varnis ...

. Another piece of glass was added to the back and this could also be coloured by hand. Both pieces of glass were bound together creating a detailed, albeit fragile, image. The process was derived from the 18th century

mezzotint Mezzotint is a monochrome printmaking process of the '' intaglio'' family. It was the first printing process that yielded half-tones without using line- or dot-based techniques like hatching, cross-hatching or stipple. Mezzotint achieves tonali ...

process.

References

* Crystoleum: Including All the Improvements and Practical Instructions for Acquiring this Popular Art Perfectly, with Full Information on the Method of Mixing and Applying the Colors, Caspar's Original Crystoleum Company, 1883 * The Focal Encyclopedia of Photography, edited by Michael R. Peres {{reflist Photographic techniques