Paper photographic prints will brown and fade with age. This example is of Colrain center, circa 1899. The yellowed area is as it appeared, when we first found it. Eventually the fine detail will ‘bleach’ away completely and will be lost. In this particular case, enough detail was still present to save it all. The black and white portion is after careful scanning and computer aided restoration. Color prints suffer the same fate, but the color information often fades much faster that the black and white component.
Paper and photographs should never be exposed to direct sunlight. Permanent damage may occur in mere minutes. Longer exposure to other light, and especially florescent light, is also bad. Avoid storing in high temperatures, or in high humidity conditions. Especially avoid any condition which causes condensation. Glossy photo prints will tend to curl and roll if they are not stored in a condition which keeps them gently pressed flat. Use acid-free document protectors or keep between acid-free paper. Ring bound books are good. Never use adhesive tape or glue on an old photo!