The preservation of photographs, and all documents and artworks, depends on the storage environment and the storage enclosures. Many institutions have climate-controlled storage rooms with purified air, kept at constant moderate or cool temperatures (e.g., 65 to 70F) and moderate relative humidity (e.g., 35 to 50%).
Some institutions even have cold vaults for certain types of photographs that are very prone to deterioration, such as color photographs and older films. Unfortunately, these conditions are not easily found or maintained in homes!
However, there are things you can do to improve the storage climate for your valuable photographs in your home: store your photographs in the coolest and driest spot in your home that stays that way year round.
Finished basements frequently are cool, but they are usually too damp for photo storage unless they are dehumidified, but there is still the possibility for flood damage or water backup.
Dampness should be avoided as it causes photos to stick together, and promotes mold growth. Above ground, interior closets maintain fairly constant temperatures throughout the year and should be considered for storage.
All plastic and paper materials used to house and store valuable and heirloom photographs should pass the ANSI IT9.16 Photographic Activity Test (PAT). (The PAT was developed by the American National Standards Institute (ANSI) and is a test that determines whether a storage material will cause fading or staining in photographs.)
In addition, other storage materials such as envelopes, folders, sleeves, and boxes should meet the standards described in ANSI IT9.2 Photographic Processed Films, Plates, and Papers — Filing Enclosures and Storage Containers.
Many manufacturers make storage materials that meet these two standards and advertise them in their catalogs.
Look for paper enclosures made from high quality, non-acidic, lignin-free paper (buffered or un-buffered are OK) made from cotton or highly purified wood pulps. Paper envelopes with center seams should be avoided — if the seam adhesive causes fading or staining it will happen in the middle of your photograph.
If you do use an envelope with a center seam, place the backside of the photo against the seam — any deterioration would have to work its way through the back before attacking the image on the front.
Look for plastic enclosures made from uncoated pure polyethylene, polypropylene, or polyester (also called Mylar D or Mellinex 516). These are considered stable and non-damaging to photographs. Polyester is clear and is more rigid than polyethylene and polypropylene.
None of these recommended plastics has any odor to them, while polyvinyl chloride (PVC) plastic does have a strong odor (the new car smell). Avoid the use of PVC plastics — they generate acids, which can fade the photograph in time.
In addition, the plastic can stick to items inside and, in some types of photographs (and printed items such as baseball cards); actually cause the image to transfer to the plastic. For these reasons, PVC enclosures should not be used for valuable photographs or those you want to preserve for a long time.
Albums are an ideal storage method for photographic prints, especially snapshots and heirloom photographs — the photographs can be safely stored and organized, and safely viewed, without inflicting damage from frequent handling. Albums should be used to store selected groups of photographs, as they are expensive and somewhat bulky storage options.
Not all photographs are really worth keeping; snapshot collections should be weeded of poor prints (blurred images, bad exposures) or less desirable photos (multiples, poorly cropped images) before housing the best ones in an album or another storage method (described below).