collotype

 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 exposed to light under a reversed negative. After the dichromate has been washed out, the film is soaked in glycerin and water. As this treatment causes swelling in those parts of the film which have been acted on by light, a plate results from which impressions can be taken with prepared ink. The albertype, phototype, and heliotype are collotypes.  [Webster 1913 Suppl.]