Nitrate base, more formally known as cellulose nitrate, was the first flexible transparent film support material used in photography, introduced in the late 1880s and widely adopted as the standard film base for both still photography and motion picture film throughout the late nineteenth and early decades of the twentieth century. It was produced by treating cellulose - derived from cotton or wood pulp - with nitric acid to create a flexible, optically clear plastic material that could be manufactured in continuous rolls and coated with light sensitive photographic emulsions, making the development of convenient roll film cameras and the motion picture industry possible for the first time.
The introduction of nitrate base film represented a transformative advance in the practicality and accessibility of photography. Prior to its development, the most widely used flexible film support was paper, which produced relatively low quality negatives lacking the clarity and dimensional stability of glass, while glass plates offered superior optical quality but were fragile, heavy, and cumbersome to handle and transport in quantity. Nitrate base provided the flexibility and light weight of paper with the optical clarity, dimensional stability, and smooth coating surface of glass, enabling the development of compact, convenient roll film cameras that brought photography within reach of a far wider public than had previously been possible.
However, cellulose nitrate film base is also one of the most dangerously flammable materials ever used in widespread commercial and industrial applications. Nitrate film is classified as a highly flammable material that ignites at relatively low temperatures, burns with extraordinary intensity and speed, and - most dangerously - contains sufficient oxygen within its own molecular structure to sustain combustion even in the absence of atmospheric oxygen, making it effectively impossible to extinguish once alight by conventional means such as smothering or the exclusion of air. Nitrate film fires burn at extremely high temperatures and can spread with devastating speed, producing toxic gases including nitrogen oxides and hydrogen cyanide as combustion products. The history of photography and cinema is marked by numerous catastrophic nitrate film fires, including the disastrous 1929 Cleveland Clinic fire in which nitrate x-ray films stored in a basement ignited, killing 125 people, and the 1978 fire at the George Eastman House film archive in Rochester, New York, which destroyed a significant portion of the world's earliest motion picture heritage.
Beyond its fire hazard, nitrate base film is also chemically unstable over time, undergoing a progressive autocatalytic decomposition process known as nitrate decay that becomes self-accelerating as the film ages. As nitrate film decomposes, it releases acidic gases - primarily nitrogen dioxide - that further accelerate the decomposition of both the film itself and any other nitrate materials stored nearby, causing the film to become brittle, discoloured, and eventually to crumble into a brown powder. The gases released during nitrate decay are also highly corrosive to metal storage containers and damaging to other archival materials stored in proximity.
The fire and safety hazards of nitrate base were recognised from an early date, and the search for a safer alternative film support began almost as soon as nitrate film came into widespread use. Cellulose acetate - marketed as safety film - was developed as a non-flammable alternative and gradually replaced nitrate base in still photography from the 1920s onwards, with the motion picture industry completing the transition to safety base film stock in the early 1950s. The handling, storage, and preservation of surviving nitrate film collections in archives, museums, and libraries remains a matter of the utmost importance to the preservation of photographic and cinematic heritage, requiring specialist storage facilities, trained personnel, and rigorous safety protocols to manage the ongoing fire and decomposition risks associated with this extraordinarily hazardous but historically irreplaceable material.