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.

10

Fix the Image

The Fixing Solution

"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, the copy should be immersed as soon as possible into a bath of hyposulphite of soda to prevent the light from exerting any further influence upon it, or as it is termed, to fix it."

"The bath is made thus: -

            -  Hyposulphite of soda, 2 ounces.

            -  Water (common), 16 ounces.

To render this bath, from the first, capable of giving tints equal to an old bath, there should be added a dram or half a dram of chloride of silver, and 40 drops of chloride of gold solution, of a strength already mentioned."

Fix for 10 Minutes of 10 hours

"Those pictures which were from the first rather faint, will be fixed after ten minutes' immersion; and darker ones may be allowed to remain for as many hours, or until they assume the desired gradation of light and shadow."

"The pictures must then be subjected to thorough washing, so as to remove completely all traces of the hyposulphite of soda bath, which will otherwise be pernicious to the permanence of the colours of the photograph.

The copies are then dried; and pressed or polished on the back."

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