Centre for Fine Print Research University of the West of England Centre for Fine Print Research
  Collotype colour print

The Collotype Archive

ISBN: 978-0-9547025-2-6

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This archive contains material relating to the photo-mechanical printing process commonly known as collotype. This process is based on the fact that the water absorbing qualities of gelatine is affected when bichromatic salts, such as bichromate of potassium or bichromate of ammonia, have been added to it, and the whole then exposed to light.

A printing plate is first covered with a substratum layer and allowed to dry. It is then covered with a layer of light sensitive bichromated gelatine and placed in a drying oven. When dry a negative is placed over the light sensitive layer and the plate is exposed to a light source. Once exposed the plate is washed to flush out the excess bichromate, it is then placed on the bed of a printing press and a damping fluid, mainly glycerine, is applied. Where the light has reached the gelatine through the negative the gelatine hardens and is no longer receptive of water, where the light was unable to pass through the negative the gelatine will still absorb water. The damp plate is then inked up, where the gelatine is dry and hard the ink will stick but it is repelled by the damp gelatine. Unlike lithography, however, where the ink is either totally accepted or totally repelled, the gelatine hardens in direct relation to the amount of light received allowing the printing plate to reproduce a full tonal range.

The archive is spilt into two main sections, the first; a reference section contains transcripts of articles taken from photographic journals contemporary with the discovery and development of the collotype process. The main sources used being the British Journal of Photography, Photographic News, Amateur Photographer and Photographic Journal. Although these journals are all British based they give a comprehensive account of both amateur and commercial use of collotype through columns from foreign correspondents detailing developments in America as well as on the Continent, especially in Germany where the process was at its most successful commercially, also included were translations of articles from foreign journals such as Photographische Correspondenz. A series of articles entitled “At Home” detailed descriptions of the working practices of European and American studios.

Included in this section is a glossary of technical terms used in the articles and descriptions of certain ingredients from the formulas. As well as transcripts of full articles this section also contains a listing of publications that either include lengthy descriptions of the process, illustrations made by the process and details of articles that there is no transcript for.

The second section, the technical, process based, section gives the recipes for the varying formulas used for both the substratum layer, the layer that helps cement the bichromated gelatine film to the glass plate, and for the light sensitive gelatine film which forms the printing surface. Detailed information or instructions regarding working the process, e.g., drying temperatures for the plates, have also been extracted from the articles and displayed here. Illustrated descriptions of the various stages in the contemporary production of collotype prints produced by the Lichtdruck Kunst studio in Leipzig, Germany, by the Alinari studio in Florence, Italy and also those produced by Dr. Thirkell at the University of the West of England, Bristol are also included.



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