PHENOSAFRANINE

In 1920 Luppo Hinricus Cramer discovered the process of development under broad daylight if the photographic material were bathed in a solution of the dye phenosafranine before immersion in the developer. This dye and others in the desensitizing family, namely methylene blue and pinakryptol, form a cloud around the silver halides and absorb light before it gets to them, so that the developing agents can only see the grains that had previously been exposed in the photographic exposure.

Because a bleached hologram is nothing more than a collection of silver halide crystals arranged in the shape of the fringe pattern, it is prone to printout. Introducing phenosafrinine to the emulsion allows the crystals to be placed under strong light without the layer darkening. See this paper for details of desensitizing experiments.

Phenosafranine is an ingredient in a couple of Ferric Nitrate Rehalogenating Bleaches, the Original Formula and Agfa-Gevaert GP431, An alcohol is part of the recipe as phenosafranine does not realidy dissolve in water.

There is no Morgan & Morgan entry for this chemical.