What is a Collotype?

Collotype is a photomechanical flat printing process used to produce varying tones and shades.

The process involves coating a glass plate in a gelatin solution, and over that a light-sensitive dichromate gelatin, which is left to dry at around 50 degrees celcius. Thereafter, the plate is exposed to light through a photographic negative. The gelatin hardens in the exposed areas, according to how much light comes through and loses its ability to absorb water. The ammonia is washed away, and the dried gelatin surface is dampened with a warm glycerin water mixture. At this point, the gelatin areas that were not exposed to light harden and swell, while the areas that received varying gradients of light exposure harden according to the level—the more light, the softer the gelatin.

When oil-based ink is subsequently applied to the plate, it is repelled by the swollen gelatin areas, and then pressed against the paper in the unexposed areas, creating the final image. Gradients of tones are also captured in this way. If multiple colors are desired, this process needs to be repeated using different plates for each of the different colors.

The fine lines and shades of tones achieved in this printing process are second to none compared with other printing techniques. Delicate original drawings and paintings which cannot be permanently exhibited due to their age and condition are often replaced by collotypes in exhibitions. These collotypes, also known as facsimiles, can be hard to distinguish from the originals even by the expert eye.

The collotype printing process was invented in 1855 by Alphonse Potevin, a French chemist and photographer who also invented photolithography. Due to its ability to reproduce fine details and color saturation, it became an evermore popular form of fine art printing in the 19th century. In 1873, Joseph Albert commissioned the construction of the first collotype press in Munich, which he patented. Collotype printing spread through Europe and America in the early 20th Century, with 200 printing studios in Germany alone. However, all endeavors to make this labor-intensive and time-consuming process economically viable for large print runs failed, and as a consequence there are very few collotype printing houses left worldwide.

Artists such as Marc Chagall and Max Ernst practiced collotype printing, as it offered plenty of room for experimentation, and for this same reason, contemporary artists have continued to take an interest in the technique. Christo’s Wrapped Roman Sculptures, 1991, Sigmar Polke’s Samson und Delilah, 1989, or Robert Motherwell’s Capriccio, 1961, are all examples of contemporary collotype printing.

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