The Wet Collodion Process

Thomas Rodger

Below are some extracts from Thomas Rodger's paper On Collodion Calotype,
 read to the Royal Scottish Society of Arts in Edinburgh in February 1854.

6

Develop the Plate

Process to produce a Negative

"After the plate has been exposed in the camera for the requisite time, it is carried back to the operating room to undergo the process of development.  The solution for this purpose is made as follows: -

Take   -  Sulphate of peroxide of iron, 480 grains

            -  Glacial acetic acid, 1 oz. (fluid)

            -  water (common), 8 ounces.  Dissolve."

"This should be poured expertly over the plate beginning at an unimportant part of the picture, and the plate should be agitated until the image appears sufficiently distinct, and intense to copy form, if a negative is wanted."

Process to produce a Positive on Glass

"If a positive on glass is desired, the plate should only be exposed for a third part of the time in the camera and should be developed with this solution.

            -  Sulphate of peroxide of iron, 96 grains.

            -  Water (common), 8 ounces.

            -  Nitric acid, 16 drops."

The Wet Collodion Process - as described by Thomas Rodger Jun.