Where and how you store your photos determines how the environment directly affects them. The main factors affecting their preservation are relative humidity, temperature, air pollution, and light.
High, low, and fluctuating relative humidity can cause image deterioration and shrinking and cracking of the binder, thus causing curling of the paper.
High temperature causes a fast rate of deterioration. Combined with high humidity and damaging effects of air pollution, many color dyes will fade and discolor. Paper will also yellow and become brittle, especially if the paper is acidic.
High temperature and humidity may also contribute to the growth of microscopic mold spores on the image. Once active mold infests a photograph it is usually impossible to remove without damaging the photograph.
Most photographic materials are also vulnerable to deterioration caused by light—both sunlight and standard fluorescent light. They are both strong sources of ultra violet light.
You might be surprised to learn that photos stored on the floor of a garage or basement are vulnerable to damage by water leaks or insects and rodents. Insects (silverfish, beetles, cockroaches) and rodents (rats, mice, and squirrels) are all attracted to photographic materials. If you have photos stored in boxes or cabinets they should be dusted or vacuumed on a regular basis. And, by all means, keep them off the floor!
Tip: If you have older photos that you treasure and want to display, have a copy made of the original and display the copy. Store the original in a safe place–away from light and humidity and off the floor. Be sure to store it in an acid-free, lignan-free envelope or album.
Watch for my next post. I will cover more on the deterioration of photos and film.