- The deterioration of a photograph may be chemical, biological, or physical in nature.
- Main factors that affect deterioration of photographs: temperature, humidity, and lighting as well as processing quality.
- Physical and biological deterioration is generally immediately noticeable, whereas chemical processes occur gradually over a period of time and the irreversible damage is not immediately visible. By the time these changes are noticeable they are usually too far gone to be reversed. This is why it is crucial to prevent potential damage by correct storage environments and close monitoring of collections.
Deterioration of BW Gelatin Silver Prints
- Chemical compounds react with the silver image – resulting in oxidation, which can then cause staining, fading, discoloration etc. POP prints are particularly susceptible as they contain smaller particles in the silver deposit layer.
- When prints are insufficiently washed and kept in a humid environment they will quickly yellow and fade.
- Sulfiding and staining are caused by inadequate washing. Fixer remains in the print reacts with high humidity and combines with the silver to form silver sulfide stains.
- Yellowing is a result of the formation of a layer of colloidal silver – due to oxidizing agents in the environment.
- Silver Mirroring: the high density areas of an image take on an iridescent sheen – visible in dark areas when viewed from the side. As a result of oxidation due to contaminants, silver mirroring occurs when the silver becomes detached from the filaments, migrates, and forms a layer on the surface.