Collotype

Collotype
Postcard with the theme of "Alte Oper" in Frankfurt am Main, about 1900.

Collotype is a dichromate-based photographic process invented by Alphonse Poitevin in 1856.[1][2] and was used for large volume mechanical printing before the existence of cheaper offset lithography. It can produce results difficult to distinguish from metal-based photographic prints because of its microscopically fine reticulations which comprise the image. Many old postcards are collotypes. While no longer a commercial process, its possibilities for fine art photography were first employed in the United States by Alfred Stieglitz.

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 gelatine and dried carefully at a controlled temperature (a little over 50 degrees 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) light source which changes the ability of the exposed gelatine 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.

To produce prints, the plate is dampened with a glycerine/water mixture which is slightly acidic , then blotted before inking with collotype ink using a leather or velvet roller. A hard finished paper such as Bristol, is then put on top of the plate and covered with a tympan before being printed typically using a hand proof press. Collotypes are printed using less pressure than is used in printing intaglio, or stone lithography. While it is possible to print by hand using a roller or brayer, an acceptable consistency of pressure and even distribution of ink is most effectively achieved using a press.

Because of its ability to print fine detail, it was also used for business cards and invitations with fine script lettering.

References

  1. ^ The Poitevin patents and the importance of using primary sources
  2. ^ Jones, Bernard Edward. Cassell's cyclopaedia of photography. Ayer Publishing. 



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Look at other dictionaries:

  • Collotype — Col lo*type, n. [Gr. ? glue + type.] A photomechanical print made directly from a hardened film of gelatin or other colloid; also, the process of making such prints. According to one method, the film is sensitized with potassium dichromate and… …   The Collaborative International Dictionary of English

  • collotype — [käl′ə tīp΄] n. [< Gr kolla, glue + TYPE] 1. a photomechanical process by which inked reproductions are transferred to paper directly from an image formed on a sheet of hardened gelatin 2. the printed reproduction …   English World dictionary

  • collotype — noun Etymology: International Scientific Vocabulary Date: 1881 1. a photomechanical process for making prints directly from a hardened film of gelatin or other colloid that has ink receptive and ink repellent parts 2. a print made by collotype …   New Collegiate Dictionary

  • Collotype — Phototypie La phototypie est un procédé d impression à l encre grasse au moyen de gélatine bichromatée et insolée sur plaque de verre. Ce procédé permet un rendu à modèle continu non tramé. Historique Procédé élaboré en 1856 par Louis Alphonse… …   Wikipédia en Français

  • collotype — collotypic /kol euh tip ik/, adj. collotypy /kol euh tuy pee/, n. /kol euh tuyp /, n., v., collotyped, collotyping. n. Also called albertype, artotype, heliotype. 1. any photomechanical process of printing from a plate coated with gelatin. 2. the …   Universalium

  • collotype printing — noun a photomechanical printing process that uses a glass plate with a gelatin surface that carries the image to be reproduced; can be used with one or more colors • Syn: ↑collotype, ↑photogelatin process • Hypernyms: ↑planographic printing,… …   Useful english dictionary

  • collotype — noun a) A dichromate based photographic process formerly used for large volume mechanical printing. b) An image produced by this process …   Wiktionary

  • collotype — col·lo·type || kÉ’ləʊtaɪp n. type of color printing used for the finest facsimile reproductions of works of art …   English contemporary dictionary

  • collotype —    A photographic printing process in which a glass plate whose surface has been coated with gelatin carries the image to be reproduced. Also called a photogelatin process …   Glossary of Art Terms

  • collotype — [ kɒlətʌɪp] noun a process for making high quality prints using a sheet of light sensitive gelatin. Origin C19: from Gk kolla glue + type …   English new terms dictionary

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