High humidity is most harmful and high temperatures accelerate the deterioration. Attics and Basements - The worst places to store your photographs or documents is in an uninsulated attic or basement. In the summer, temperatures in an attic could reach 125 degrees F. while in the winter they can get down to less than 0 degrees. With the constant high temperatures and humidity in the summer and low temperatures and humidity in the winter, the photographs or documents will become brittle. These cyclic conditions will have a devastating effect on any paper product.
Uninsulated basements are usually moist which can cause photographs to stick to each other.
Another problem encountered in basements is that they are great breeding grounds for insects and rodents which are strongly attracted to gelatin and cellulose in the photographic emulsion. The best places to store important photographs or documents are in a safe deposit box at your bank. They are usually climate controlled and kept dark to provide almost ideal storage conditions. Wood, Paper and Paper Products - Wood and papers contain harmful additives such as bleach or hydrogen peroxide. Use only paper products that are acid free.