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.

9

Expose the Paper

Ammonio-nitrate of Silver

"The ammonio-nitrate of silver is made as follows: -

            -  Nitrate of silver (crystallized), 110 grains.

            -  Rain water (pure), 3 ounces.

Shake till all the crystals ae dissolved, and then add liquor ammoniae (fortissimus) in small quantities till the precipitate at first formed is almost entirely redissolved."  

"Should too much ammonia be added, a few crstals of nitrate of silver will bring back the turbidity, in which condition I find it most suitable."

The frame used for Exposure

"The pressure frame I use is of the simplest construction.  It consists merely of a cross-haired flat board, to which is attached by hinges a frame containing a square of plate glass; the pressure being given by a pinching screw."

"When the  negative and sensitive sheet of paper underneath have been exposed to the action of the sun's rays long enough to make the copy a shade or two darker than is intended to be when finished,  ... [continued on NEXT PAGE]