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

albumen print Egg white is the clear liquid (also called the albumen or the glair/glaire) contained within an egg. In chickens, it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms aro ...

, 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 diet ...

paste or

gelatin Gelatin or gelatine () 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 be referred to as hydrolyzed collagen, coll ...

) 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. Oil paint also has practical advantages over other paints, mainly because it is waterproof. The earliest surviving ex ...

. 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 (printmaking), 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. Mezzo ...

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