Source : Webster's Revised Unabridged Dictionary (1913)

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 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.

Source : WordNet®

collotype
     n : 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
         printing}, {photogelatin process}]