As a specialist in the field of film history and preservation, I can provide an insightful analysis of why old film was particularly flammable. The primary reason for the flammability of old film lies in its composition, specifically the use of cellulose nitrate as a base material.

Cellulose nitrate, also known as nitrocellulose, is a highly flammable compound that was widely used in the production of photographic and cinematographic film during the late 19th and early 20th centuries. It was favored for its transparency, ease of processing, and ability to hold a fine grain, which resulted in high-quality images. However, the very properties that made cellulose nitrate an excellent film base also made it extremely dangerous.

The flammability of cellulose nitrate film increases with age due to a process known as "decomposition." Over time, the nitrate groups within the cellulose molecules break down, releasing nitrogen oxides and other volatile compounds. This decomposition process can be accelerated by heat, humidity, and physical stress, all of which are common in storage and handling conditions. As the film ages, it becomes more brittle and prone to spontaneous combustion.

Another factor contributing to the fire risk is the presence of other flammable materials often associated with cellulose nitrate film. Archival materials, such as adhesives, dyes, and other chemicals used in the film's production, can also be flammable and can exacerbate the fire risk.

The storage and handling of cellulose nitrate film require strict safety measures. It must be stored in a cool, dry, and well-ventilated environment, away from any sources of heat or ignition. Even under ideal conditions, the shelf life of cellulose nitrate film is limited, and many archives and film preservation facilities have had to undertake extensive efforts to safely store and migrate their collections to safer materials.

The transition from cellulose nitrate to safer film materials, such as acetate and polyester, began in the mid-20th century. Acetate film, while still flammable, is less reactive and has a longer shelf life than nitrate film. Polyester film, introduced later, is even more stable and less prone to combustion, making it the preferred material for modern film production and preservation.

In summary, the flammability of old film is primarily due to the use of cellulose nitrate as a base material. Its decomposition over time, coupled with the presence of other flammable materials and the conditions under which it is stored and handled, contribute to the high fire risk associated with old film. The shift to safer materials in the mid-20th century has greatly reduced the risk of fire in film archives and collections.

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This is a problem because the high fire risk from cellulose nitrate film increases as it ages. Old cinematographic film and old photographic negatives (including X-ray film) may be made from cellulose nitrate (which means they contain nitrated cellulose, or other nitrated product).read more >>