Cellulose nitrate based films were produced in the early 20th century until 1952. They were developed to replace glass plate negatives, and used for black and white motion pictures. Nitrate based films are inherently unstable and will deteriorate in temperatures around 70°F and humidity greater than 50%. While deteriorating, the films off-gas potentially flammable fumes. These collections are a particular danger due to their ability to spontaneously combust – chances of which are increased if stored in improper environmental conditions and sealed containers.
Identify which films in a collection are made of nitrate so that staff members are alert to which films are the most hazardous. Nitrate films are never paper-based but may be hard to distinguish between acetate and polyester films. The Kodak Company’s website lists techniques to identify Kodak nitrate films, by:
- Comparing film edges
- Using ultra-violet light to detect fluorescence
- Smelling the storage area for an acidic odor
As the films deteriorate, they change physically as well as chemically:
- Turning a yellow or tan color
- Becoming brittle, sticky, or even powdery, depending on the extent of deterioration.
- Developing a pungent odor through the off-gassing of nitric oxide or nitrogen dioxide
The flammable nature of nitrate films is not the only health hazard to those working with the collection. Exposure to the noxious off-gassing of nitrate films may cause skin and lung irritation, nausea, or headaches for staff members. Other objects stored around the films may be affected by off-gassing as well, leading to deterioration of storage boxes and objects.
The following guidelines are recommended for long-term storage of nitrate based films:
- Remove badly deteriorated films from the collection; they are a safety hazard and have lost their physical integrity and historical information.
- Do not store nitrate based materials in tightly-sealed containers that would lead to pressure build-up.
- Store nitrates separately from all other photographic materials to prevent further collection damage in the case of fire.
- Do not overcrowd the storage containers, as too much nitrate film in one place increases the risk of fire.
- Store in cold storage vaults with precise temperature and relative humidity control and good ventilation. Recommended conditions are temperatures below 40°F and humidity between 20-30%.
- If cold storage is cost prohibitive, frost-free freezers are an acceptable alternative.
Many museums, including the American Museum of Natural History, follow specific guidelines set by the National Fire Protection Association (NFPA), specifically, code NFPA 40. See the Case Studies section for more information on how the AMNH has set up nitrate film storage facilities. [use images Health & Safety Images (12) and (13)]
For information on the proper disposal of nitrate films, see the National Park Service’sConserve O Gramon the topic, listed in the Additional Resources section below.
The New York Historical Society experienced the hazards of deteriorating nitrate films first-hand when their collection of films caught on fire in 2003. An article in the New York Times about the fire is available on-line at:
The Arizona State Museum received anNEH Preservation and Access Grant enabling the re-housing of about 7,800 nitrate negatives into proper storage containers. More information on the project is available on-line at:
The American Museum of Natural History equipped their nitrate film storage area with several safety precautions that meet regulations set by the New York Fire Department, based upon the regulations outlined by the National Fire Protection Association (NFPA) code 40, including:
- Bagging the films separately in polyethylene bags
- Storing the bags in freezers and marking the area with hazardous materials signage
- Outfitting the storage area with fire safety equipment (fire extinguishers and sprinklers). [Image Health & Safety
- For specific information on the NFPA 40 regulations, consult the code handout “NFPA 40: Standard for the Storage and Handling of Cellulose Nitrate Film”, available for purchase on-line at the NFPA website.
- The Kodak Company’s website offers a wide scope of information on nitrate films in their section on “Storage and Handling of Processed Nitrate Film”
- Several of the National Park Service Conserve O Gram leaflets listed in the section on Photographs provide specific information on this topic, as well as the section on Security, Fire, and Curatorial Safety. These leaflets are available online here. Of particular interest on this topic are:
- The Health and Safety Executive in the United Kingdom provides a pamphlet on The Dangers of Cellulose Nitrate Film
Library of Congress. “Care, Storage and Handling of Photographs.” Information Leaflet.
Messier, Paul. “Preserving Your Collection of Film-Based Photographic Negatives.” Rocky Mountain Conservation Center.
Reilly, James. 1993. IPI Storage Guide for Acetate Film. Image Permanence Institute, Rochester Institute for Technology. Rochester, NY.