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What causes this to film?


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  • 3 weeks later...

The damage to the image appears to be similar to what I've heard termed as "silver clad" or "silver plate-out".  This is found on old black & white images of film or paper that have been exposed to high humidity and vapors that contain sulpherous compounds.  The atoms from the atomosphere work there way into the image and attack the silver turning the metallic silver into silver ions and silver sulfide and the silver actually moves up to the surface of the film / paper sometimes leading to a metllic mirror-like finish on the film / paper as well.  Improper fixing and washing at the time of development may leave trace chemicals inside the emulsion structure that increase the rate of decay, and other things such as handoils from fingerprints, talk spots, etc. can also affect that rate of decay.  The "plate-out" seems to associate at the boundaries of heavy and light density, perhaps because the heavier density with its greater amount of silver in the remaining gel structure, acts as a giver (of silver) and as a barrier for allowing those compounds from entering the image structure. Thus, this could be considered a boundary layer problem.

I do know that the earlier films did not contain overcoat layers nor the level of hardeners as do modern films; both of those to aid in reducing the migration of unwanted compounds from affecting the metalic silver of the image.  This affect is not present in color film because all of the silver in color film is removed during processing.

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