Photography - Film Development

When the films are developed rinse them in three changes of water, and then pass them into the acid fixing bath. This can be made up from the perpared fixing powders, which only call for the addition of water; or by the student himself, according to the following formula: Formula for Acid Fixing Bath. Water 16 ounces Hyposulphite of Soda 4 ounces Sulphite of Soda 80 grains When this is fully dissolved add: Powdered Alum % ounce Citric Acid % ounce In place of the Citric Acid you may use ^ ounce Acetic Acid, but you must be sure that it contains 25 per cent, pure acid, This bath can be used repeatedly so long as it retains its strength and remains sufficiently clear not to stain the film. The regular acid hypo fixing bath can be purchased in powdered form, ready for use, from any photographic stock house. There should be sufficient fixing solution in your tray to completely cover the films when immersed during the entire process of fixing, as otherwise the films will fix unevenly and stains will be produced if they are left partly exposed to the air. Non-curling films can be fixed in the plain hypo bath recommended for plates but when using this bath the films must be rinsed in three changes of clear water after fixing, and then placed into an alum bath prepared as follows: Water 16 ounces Alum (crystals) 1 ounce Of this solution decant into a tray enough of the clear liquid to cover the films, and allow them to remain in this bath for five minutes; then wash in the ordinary manner. The alum hypo bath can be used continually until it becomes discolored or so exhausted that it will not harden the film.