The wet Collodion is a photographic process invented by English Frederic Scott Archer in 1851.

History

This process knew a great popularity until the years 1870 - approximately 1880 because it made it possible to obtain stereotypes of a large smoothness and to make a range of gray particularly wide.

It presented however a major disadvantage: the negative one was to be prepared, exposed, then developed in a very short time, because once dry it became insensitive and, if the catch of sight already had been made, impossible to develop. According to the conditions of ambient temperature and moisture, the operation was not to exceed from 15 to 30 minutes on the whole.

Composition - Development

The Collodion is a Nitrate of cellulose dissolved in a mixture of alcohol and ether which one extends on a glass plate. When this sirupeux mixture starts to solidify on glass, one plunges the plate in a bath of Silver nitrate to sensitize it, the salts contained in the film are thus transformed into money halide sensitive to the light. One drains the plate then, transfers it in a frame tight with the light. These operations are done obviously in darkroom. One can then make a catch of sight with the photographic Chambre. The plate must then be immediately developed in darkroom with gallic acid or ferrous sulfate II then fixed at sodium thiosulfate or potassium cyanide.

This operation was done in a part lit in red light clearly, collodion being achromatic.

This process was used in photoengraving until the years 1950 and more,

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