Early film base made from cellulose nitrate — highly flammable and self-igniting when degraded. Why silent-era stock spontaneously combusts in vaults.
Cellulose nitrate was the base material for early cinematography—and a damn safety hazard. From the late 19th century until around 1951, most feature films, documentaries, and newsreels ran on this material. The problem: the stuff is chemically unstable. It decomposes on its own, releases toxic gases, and can ignite itself if decomposition is sufficient—without an external flame, just through chemical reaction. This isn't theater. This is reality in every film archive that stores old reels.
Practically speaking: a reel of nitrate film stock requires special storage conditions—stable at 4–5 degrees Celsius, low humidity, ideally a nitrogen atmosphere in sealed containers. If you're restoring old films in an archive today, you immediately encounter the chemical question. Many historical reels are already in advanced decay—you can recognize it by the smell of vinegar, by discoloration, by a white crystalline deposit on the film itself. This is cellulose nitrate in its final phase.
The practical consequence for the mastering process: such archives scan or transfer nitrate film stock under controlled conditions, often underwater or with special carrier systems, to minimize mechanical stress and heat input. You can't just throw an old reel into a projector—the thing is too fragile, too dangerous. Most major archives work with specialized service providers who have the necessary infrastructure.
This is also the reason why so many early films are actually lost. Not just because nobody preserved them—but because the material is physically beyond saving. Nitrate film stock is a treacherous medium: it looks relatively stable at first, then the decomposition accelerates exponentially. On set or in the lab back then, you didn't need special safety precautions—that was everyday life. Today, it's a conservation and safety issue that puts archives worldwide under pressure. The fight against time here is literally chemical.