Collotype

In Poitevin's process, a lithographic stone was coated with a light sensitive gelatin solution and exposed to photographic negative.[5] The gelatin would harden in exposed areas, leading to the stone becoming hydrophobic in light areas (and thus, ink-repelling) and hydrophilic under dark areas (ink-attracting).[4][5] The stone was then printed via the standard lithographic process, producing a monochrome print.

In 1865, Tessie du Motay and C. R. Marechal applied the gelatin to a copper plate, which was easier to handle than a lithographic stone.[4] However, the gelatin did not adhere well and limited print runs to about 100.[4]

In 1868, Joseph Albert and Jakub Husník applied a gelatin-albumen mixture to glass, which was then coated with light-sensitized gelatin.[4] This allowed print runs of up to 1,000.[4] This patent was later purchased by Edward Bierstadt, who developed one of the first commercial collotype companies in New York City.[6]

Example of a collotype ("Phototypie" in the caption) printed in blue ink. This is a monochrome collotype, not a color collotype.

The collotype plate is made by coating a plate of glass or metal with a substrate composed of gelatin or other colloid and hardening it. Then it is coated with a thick coat of dichromated gelatin and dried carefully at a controlled temperature (a little over 50° Celsius) so it "reticulates" or breaks up into a finely grained pattern when washed later in approximately 16 °C water. The plate is then exposed in contact with the negative using an ultraviolet (UV) source which changes the ability of the exposed gelatin to absorb water later. The plate is developed by carefully washing out the dichromate salt and dried without heat. The plate is left in a cool dry place to cure for 24 hours before using it to print.

Related processes, or processes developed from collotype, or even alternate names for collotype include albertype, alethetype, autocopyist, artotype, gelatinotypy, heliotype, hydrotype, indotint, ink-photo, leimtype, lichtdruck, papryrotype, photogelatin, photophane, phototype, Roto-Collotype, Rye’s, and Sinop.[7][4][8]

In 1874, Joseph Albert produced the first color collotypes with three collotype plates, each inked in a different color.[4] In 1882, the Hoeschtype, which used six plates, was patented.[4]

Reproductive collotype of a wood engraving of the British Museum.

The Mezzograph collotype was a trade name used by Valentine Co. Ltd. of Scotland, for their multicolored postcards, printed in a hybrid process where colors were printed via photolithography and then overprinted in black or blue collotype for the "outlines" of the image.[4]

Halftone collotype processes combine halftone printing and collotype. These include the Jaffetype, developed in Vienna; the Aquatone, developed and patented by Robert John in the United States in 1922; the Gelatone process, introduced in 1939; and the Optak process, introduced in 1946.[4]

In 1997, there were no commercial collotype printers in the United States.[7] As of 2015, there were only two commercial collotype printers in the world, both based in Kyoto, Japan.[12]

In 2010, only a small number of facilities in the United States, primarily art studios or organizations, still have the ability to create collotypes.[4]

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  Pretty Nose, collotype with black ink, 1879.
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  Collotype (on left page), 1887.
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  Collotype reproduction of original painting by Henry Sandham, 1896.
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  Collotype in black ink of a painting, 19th century.
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  Collotype with green ink, 1908.
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  Collotype in sepia ink, 1913.
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  Collotype in blue-grey ink.

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  Hand-colored collotype, 1896.
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  Collotype with handprinted color, 1900.
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  Edward Burne-Jones' The Flower Book (1905), collotype with applied pochoir.
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  Collotype (of an engraving) with applied watercolor, 1913.
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  Postcard of Biarritz, collotype print with applied color, ca. 1916.
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  Hand-colored collotype, ca. 1877-1920.

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  Collotype with brown and blue ink.
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  Lobby card of Mary Pickford, 1921.