Gum bichromate printing, one of the oldest photographic processes still in use, offers a way of creating color prints from black and white negatives. Gum bichromate emulsion–potassium dichromate and ...

TAKE a glass vessel, a porous cell, a zinc rod and a carbon plate, such as are used in the ordinary Leclanché cell (a circular glass vessel of the same capacity is better). Prepare a solution of 20.4 ...