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Using photographic patents as a source of information

Trying to find relevant sources of information for the surface relief properties of gelatin, Paul A. Lehman finds an unusual source to find answers: The patent archives. He shares his findings here. Each patent provides detailed information on emulsion ingredients, preparation and processes, which can be reproduced in a suitable home darkroom laboratory. Writer and photography / Paul A. Lehman Color and Gelatin Relief Emulsions U.S. Patents Issued to Michele … Read more