The POP Silver Gelatin Process

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Process Description
The POP silver gelatin process involves the following steps:
1. POP photographic paper is placed under a negative into a special copy frame.
2. The copy frame assembly is exposed to daylight or artificial light until the image is developed to the desired image intensity. Guides for approximate exposure times were usually available from paper manufacturers for different lighting conditions, but some tests were needed to find good exposure conditions for a given light and negative combination. POP requires some level of overprinting because the image intensity is decreased during processing.
3. The exposed POP is washed in a water bath to remove any excess of soluble silver salts.
4. The washed POP is toned using different types of gold and platinum toners or using first a gold, then a platinum toner. Some toning formulas found in early nineteenth-century photographic literature also recommend using palladium or iridium toning. However, even after analyzing thousands of POP silver gelatin photographs, we still have not identified any existing photograph toned in that manner.
5. The toned POP photograph is washed again to remove toning chemicals and fixed using the standard hypo (sodium thiosulfate) fixer.
6. The toned and fixed photograph is thoroughly washed in running water or in multiple water changes in a water tray.
7. The washed photograph is air dried or surface polished by squeegeeing the print on a clean, polished glass and letting it dry. The fully dried photograph usually separates from the glass surface on its own.
DOP SILVER GELATIN PROCESS
The main difference between the POP and DOP silver gelatin processes is not in the internal structure of the photographic material but in the way the silver-base...

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...y and could be viewed only by reflected light, however, researchers continued to look for improvements and alternative colour processes.
In 1935 Leopold Godowsky, Jr., and Leopold Mannes, two American musicians working with the Kodak Research Laboratories, initiated the modern era of colour photography with their invention of Kodachrome film. With this reversal (slide) film, colour transparencies could be obtained that were suitable both for projection and for reproduction. A year later the Agfa Company of Germany developed the Agfacolor negative-positive process, but owing to World War II the film did not become available until 1949. Meanwhile, in 1942 Kodak introduced the Kodacolor negative-positive film that 20 years later—after many improvements in quality and speed and a great reduction in price—would become the most popular film used for amateur photography .

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