There are a thousand and one formulæ for developing solutions for
the wet plate, but they are all composed of protosulphate of iron or
a compound thereof, acetic acid, and water, with the addition of
some organic substance, such as sugar, rock candy, glycerine, etc.
etc.
The development of a negative is nothing more than the deposition of
metallic silver in a state of fine sub-division upon a base of the
same metal, which is the image latent in the collodion film after
exposure in the camera. And it is supposed that the finer the
deposit [p034] secured in the development the better will be the
chemical effect and printing quality of the resulting negative.
Therefore, the use of organic bodies in the developer is supposed to
effect or induce a finer deposit. The careful observer, however,
will soon discover that the success of the development depends more
on the time of exposure, the temperature of the developing solution
and the condition of the bath, than upon any adventitious aids, such
as rock candy, etc.
A developing solution, composed alone of an aqueous solution of
protosulphate of iron and acetic acid, can be made to produce the
finest effects possible to the process.