All film stocks decompose over time. Sometimes this decomposition is irreversible — which explains why an estimated 75% of American silent films are considered lost.
The Eastman Museum runs one of the world's top film-preservation programs. Its archives of over 28,000 films include the personal collections of directors like Spike Lee and Martin Scorsese and carefully controlled nitrate vaults containing over 26 million feet of film. The museum's preservation projects include the silent films of Cecil B. DeMille and Georges Méliès, along with Stanley Kubrick's first film, "Fear and Desire," from 1953, and Orson Welles' once-lost work "Too Much Johnson," from 1938.