Structure of Photographs
Photographs are made up of:
- a support – usually glass, plastic, paper or metal;
- a binder/emulsion layer – albumen, collodion or gelatin; and
- the final image material – suspended silver, platinum, colour dyes or pigments in the emulsion/binder layer.
The composite nature of photographs complicates their care as the respective needs of the various components must be catered for. The paper support for instance will be strongly affected by fluctuations in relative humidity levels, the binder may shrink or crack if the relative humidity is too low and the dyes may be affected by inappropriate light levels (see Deterioration/Conservation next).