Photo prints, slides and negatives are made by using chemicals and chemical dyes. Unfortunately they are sensitive to light, moisture and changes in temperature. Their life span depends on the care taken with handling and storage, and also the type of film used and the process used to create the film.
Most casual photographers used regular colour slide and negative film which was processed in quick and convenient mini-labs and placed into cheap plastic sleeves.
Generally images over 20 years old will develop colour changes, lose detail and become grainy. The best way to store them is in a cool, dark, dry environment. However, all slides and photos will deteriorate over time. By far the best thing you can do is to have them scanned to digital images.
35mm slides, or transparencies, are small pieces of positive film encased in a 2 inch piece of plastic or cardboard. They were invented in 1935 and were in general use in the 1960s through to the mid 1990s. They were a popular way to create high-quality projected images.
The dyes used to make the slides are not stable and they slowly lose their colour, and eventually become transparent. For example, yellow dye is notorious for its rapid loss of colour which can then make skin colour look red or purple. This is more evident if low quality products and processes were used. In comparison, Kodak developed Kodachrome in 1936 which used a more stable dye process.
Excess light, heat and moisture will affect the dye colour layers in a slide and will encourage mould. If the film has been touched with fingers it can cause fungus to grow.
If you choose not to digitise them, it is advisable to keep them in polyester sleeves, then store them in a cool, dark, dry environement.
Loose photographs, and photos in albums, are affected by fluctuations in temperature, light and humidity. UV light affects the chemical makeup by breaking down the the chemical bond of the dye, causing colours to fade. Photos stored in albums may bond to the page or stick to the clear, protective sheet. Quality PVC-free plastic sleeves are the best solution. Then store them in a cool, dark dry environment – but not a garage as they may be exposed to gases such as nitrogen oxide and sulphur dioxide.
Loose photographs are prone to dust and scratches. Older photograph albums tend not to have protective sleeves or plastic covers and are prone to dust build up. This may cause abrasions on the photo surface when the album is handled.
Scanning and saving to digital images not only means that they are safe from further deterioration, but also means that they can be viewed and shared easily with family and friends.