It has only been a little over 150 years since the invention of photography and over that time dozens of different photographic processes have been used. Each type of photographic print and negative has its own specific handling and storage needs, but there are certain common factors that affect the longevity of all types of photographs. The following are suggestions that will help slow the deterioration of your photos, so the images can be enjoyed by future generations.
- Control relative humidity and temperature. Critical to the preservation of any type of photograph is the tight control of relative humidity conditions and temperatures. Harmful chemical reactions that lead to fading and discoloration of your photographs can be accelerated by high relative humidity. On the other hand, extremely low relative humidity can cause photographs to curl and crack. With every 10 degrees F increase in temperature the rate of chemical deterioration is doubled in most photographic materials. Mold growth and insect activity increase when temperature and relative humidity are at high levels. Fluctuations in relative humidity and temperature can result in emulsion cracking and general structural damage to the photograph. Most photographic prints should ideally be stored at temperatures less than 70 degrees F with a temperature fluctuation of no more than 2 degrees in a 24 hour period and at a relative humidity of between 30% and 50% with no more than a 5% change in relative humidity during the day. Generally storage in an interior room is much better than in an attic or basement.
- Control light levels. Light can cause yellowing, fading, and embrittlement in photographs and the damage is cumulative and usually irreversible. All forms of light are damaging to photographic prints and negatives and exposure should be moderated. The ultra-violet radiation from unfiltered sunlight and fluorescent lights are often the most harmful, but damage from these sources can be reduced with UV-absorbing sleeves over the windows and fluorescent tubes, and UV-filtered glazing over the photograph. If the photograph is on display, always use a copy, never the original photograph. Black & White images tend to deteriorate less quickly than color photographs, but all images will fade with prolonged exposure.
- Control dirt and air pollution. Contaminates in the air can damage your photographs, causing fading and abrasion. Good air circulation, and control of the amount of dust present in the storage area can slow down deterioration of your photographs. If you live in an urban environment, air filtration is a necessity. Particulates can be filtered mechanically, but chemical (gaseous) pollution must be removed by wet scrubbers or chemical filters. Many products off-gas as part of their own deterioration process and these gases can harm your photographs. Keep your photographs away from paints and chemical supplies, unsealed wood shelving or drawers, and photocopying machines and laser printers. Metal cabinets are preferred to hold photographs as wood can generate harmful peroxides.
- Control handling. Breakage, tears, and abrasion of photographs can result from careless handling. Oils from your hands can react chemically with the photographic emulsion causing silver mirroring or bleaching. It is best to handle photographs with clean, white cotton gloves to minimize damage. Paper or plastic enclosures are essential for the negative or print's long-term stability. Prints can be labeled by enclosing a piece of acid-free paper in the enclosure. If you must label the photograph directly, always label on the edge of the back side lightly with a lead pencil. Avoid photo contact with adhesives. Never use tape, rubber cement or "magnetic" self-sticking photograph albums. Paper enclosures should be composed of acid-free paper and Kraft or glassine paper should be avoided. Paper enclosures can act as a buffer against changes in humidity, but as they are opaque, damage from increased handling for viewing may result. Plastic enclosures should be made of uncoated polyester, polypropyl, or polyethylene. Polyvinyl chloride (PVC) enclosures off-gas as they age and will hasten photographic deterioration. The proper plastic enclosure should not have an odor, PVC enclosures smell like shower curtains. Avoid clipping together photographs with paper clips or rubber bands. Both will damage photographs in a relatively short period of time. As a general rule, prints are best stored horizontally and most negatives should be stored vertically. Materials of similar size should be stored together and placed in a box or cabinet drawer of a size larger than the photograph. Photographs should never be rolled or folded. Always store them flat.
For more information about protecting your documentary heritage, please contact:
The Rochester Regional Library Council
390 Packetts Landing
Fairport, NY 14450