Environmental aspects of photographic storage constitute an important element in the achievement of long-term preservation. The rate of degradation of most photographic materials varies with humidity, temperature and exposure to light. Photographic images should therefore be stored in a cool, dry, dark and well-ventilated environment. Avoid storing valuable images in an attic or basement, or against the external walls of a building, where large variations in temperature may occur and condensation may form.
Exposure to light, particularly sunlight, is likely to cause rapid fading in film-based images. Some fading may also take place in complete darkness, especially where a photographic process is very acidic. It is therefore advisable to make copies of original images and use only the second-generation images for display purposes. Ultraviolet filtering glass helps to protect displayed imaged from harmful UV rays.
Fading is still an issue even with modern ink-jet prints. There are basically two fading mechanisms - light fading and air fading. Light fading is caused by the light falling on the image surface gradually breaking down the molecules that produce the visible colours. If the image is stored in complete darkness, this process is halted. Air fading affects mainly porous prints which absorb pollutants, such as ozone, into the exposed pores of the surface of an image. The pollutants get into the small particles in the porous coatings and slowly attack the dyes.
Prints, slides and negatives can be stored in folders, sleeves and pockets to avoid physical damage. However the storage media should be chemically stable and ideally free of sulphur, acids and peroxides. Such materials are available from specialist conservation suppliers. Strips of film-based negatives should be stored separately from other photographic materials as they produce acidic gases as part of their aging process.
Careless handling of photographs is a major cause of damage. Fingerprints leave perspiration and oily stains on emulsions, and particles of dirt and dust scratch surfaces and may act as a catalyst for unwanted chemical reactions. Poor quality storage materials, including PVC, acidic mounts and backing boards, magnetic or self-adhesive albums, and new wood frames, can all accelerate deterioration. Self-adhesive tapes, paper clips and rubber bands are also all best avoided. Unprofessional cleaning of photographic materials can also cause serious and irreversible damage.
Photographs should always be handled very carefully, but particular care should be taken to avoid all contact with the image surface. Wearing clean, lint-free cotton gloves lessens the possibility of leaving fingerprints or other damaging deposits. Large photographs should be supported with both hands or on a backing card to avoid creasing. Avoid marking prints with ink of any type - use an HB pencil lightly on the reverse side.