Each type of document has its own unique needs in regards to storage and preservation. Photographic materials are particularly challenging because of the variety of techniques used to preserve images on film and the different ways that they change with time and deteriorate. While photographic prints are more resilient, the film requires special storage and handling. Cold storage for the film is a popular preventive conservation measure that extends the life of historic film and averts the need for costly restorations.
What Happens to Film as it Degrades
When stored in humid or warm conditions, or experiences frequent handling, the older film becomes defective. It may acquire a vinegar-like scent as the cellulose degrades and releases acetic acid. When one film releases acid, it threatens the surrounding film.
Moisture poses one of the greatest threats to film, as it only takes a few days for film and negatives to begin degrading and change in color when exposed to water or high humidity levels. With time, bacteria and mold cause the properties of film to separate, dissolve and decompose.
Cold Storage for Film
In general, cold storage areas for film and photographs are between 0° and 55°F and have appropriate relative humidity levels. “Cool rooms” are between 55° and 65°F and have relative humidity levels of 30 to 40 percent. The best temperature at which to store film depends on its type, achievability, and condition. Some facilities use dedicated cold storage areas for large collections, while others use refrigeration or freezer units for smaller collections.
At the Federal Archives, cold storage at 35°F or below with relative humidity levels of 30 to 40 percent is standard for the film, color photographic materials, transparencies (e.g., slides), prints, and negatives that it maintains for extended periods.
It is important to remember that if you have access to film and photographic materials kept in cold storage, you must first acclimatize it to room temperature using plastic bags or insulated containers.
Benefits of Cold Storage for Film
- Dramatic increases in dye and color stability
- Lowering relative humidity levels in a storage area may double the life expectancy of the film; using cold storage further extends its life (At 10°F and relative humidity levels of 30 to 50 percent, for example, the film may last over 3,000 years before it deteriorates.)
- Cold storage with the appropriate humidity levels prevents curling and mold growth on photographic prints
- Keeps film collections “in stasis” until they’re restored, preserved, or duplicated
- Deteriorated photographic prints, albumen prints, brittle and faded prints, and prints that were poorly processed benefit from cold storage areas that have below-freezing temperatures
- Black and white silver gelatin film-based materials and photographs benefit from cold or cool storage
- Cool storage where temperatures don’t reach freezing levels are good for instant prints (e.g., Polaroid prints), cased photographic images, lantern slides, and glass plate negatives
- You can design cold storage areas with climate control systems that filters air, monitor the environment, and protect films in the event of fires and water infiltration
- Environmental controls in cold storage can protect images from oxidation, ozone exposure, light exposure, gelatin yellowing, image fading, and silver mirroring
It is common to for facilities to use HVAC systems to create the ideal environment for their film and photographic archives. This, however, may not be ideal in regards to energy efficiency or fully protecting collections. A better alternative may be to have an independent system that controls and monitors cold storage room environments. Similarly, an organization may use temporary climate control solutions that complement an HVAC system to monitor and ensure the appropriate environmental conditions in space. Polygon offers a variety of custom climate control and monitoring solutions that provide you with the ability to reliably provide cold storage for film and reduce energy costs. Contact Polygon to learn more about creating the ideal storage environment for photographs and film.
[Photo from Hartwig HKD via CC License 2.0]