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Printing Chemistry
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 Printing Chemistry


Janice Clifton, CRA COT
Seattle, Washington


Paul R. Montague, CRA FOPS
Iowa City, Iowa

Photographic Illustrations by
Peter Buch, CRA
Buffalo, New York


Photographic paper has roughly the same anatomy as film: It is a light sensitive emulsion coated on a base. Instead of the clear acetate base used for film, a fiber or resin coated base is used for prints. The emulsion used for photographic prints is not sensitive to all wavelenths of light, making it save to handle photographic paper under safe light conditions without danger of exposure.

Although paper emulsions differ somewhat from film emulsions, the basic chemical process is the same. The paper is exposed beneath an enlarger creating a latent image on the paper. The exposed paper is then processed in a developer which reduces the exposed silver halide to solid silver, as with film. The developers for paper can produce warm or cold tone prints, and their chemical make-up differs from film developers. The stop bath and fixer are identical to those used for film, as is the optional hypo clearing agent. Wetting agents like Kodak Photo Flo are not used for paper prints.

A wide variety of paper developers are available. The choice of developer has a great effect on the tonal quality of the print. There are high contrast and low contrast developers and there are warm tone and cold tone developers. Angiographic prints can be processed with acceptable results in many of them.

A warm tone and a cold tone developer have been chosen as examples. All of the following chemistry is furnished in liquid form for ease in preparing working solutions. The solutions other than the developer are the same as those recommended for film processing.

Paper Processing Chemicals

Cold Tone Developer

 

Kodak Polymax T

Warm Tone Developer

 

Kodak Ektaflo Developer, Type 2

Stop bath

 

Kodak Indicator Stop Bath

Fixer

 

Kodak Rapid Fix

Hypo clear

 

Hustler Rapid Bath

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