The film industry today is one of the major staples of American culture. So much so, that in 1988 the National Film Preservation Board (NFPB) was created by an act of Congress, and has been renewed as late as 2008. One of the NFPB's jobs is the maintain the National Film Registry "to ensure the survival, conservation and increased public availability of America's film heritage." Films have had a very difficult history of preservation. Many studios and print companies disposed of their old film stock to conserve space and prevent fires . Cellulose nitrate was the first plastic backing made for film, and worked well in cameras as a jam would primarily break the film first. However, cellulose nitrate has another use: guncotton, so naturally it ignites very quickly. In fact, the present day director, Quentin Tarantino, actually used cellulose nitrate's flammability as a plot tool in his film Inglourious Basterds (2009) where a projectionist burns down her theater during a Nazi propaganda film to kill Hitler. This material property also sheds new light on former supreme court justice Oliver Wendell Holmes Jr.'s opinion in Schenck v. United States (1919) comparing some types of speech to "shouting fire in a crowded theater" making it a more natural danger then we may think cinema fires are today (or it could have be an attempt at a culture reference like Justice Elena Kagan's dissent in Lockhart v. United States where she references Star Wars: The Force Awakens and the newest Zoolander). One of the largest cinema fires happened at the Glen cinema in Paisley, Scotland on December 31, 1929 during a children's production when a reel of a freshly shown film auto-ignited killing 71. This might have been assisted by the fact that as cellulose nitrate degrades it releases nitric acid and a flammable powder, increasing the likelihood of an auto ignition, making the storing of cellulose nitrate films difficult. One of the greatest disasters in film preservation happened in 1978 when the National Archives and Records Administration and the George Eastman house lost 12.6 million feet of newsreels and 329 feature films respectively. However, the degradation can be slowed indefinitely by storing at low temperatures.
Nitrate film was replaced by acetate film start in the 1950s. While the replacement does not spontaneously ignite, it did present a different challenge to film preservationists. Like nitrate film, the degradation of acetate films produces an acid, in this case acetic acid, that accelerate further degradation. This occurs faster in hot, moist, acidic environments. This then causes the cellulose triacetate backing to become brittle and shrink, causing the gelatin emulsion to separate from the backing. Bubbles then may form on the emulsion as plastisizers leach out of the backing. Finally, some antihalation dyes turn blue or pink in the acidic environment. Like nitrate film storing the film in cold dry environments dramatically increases its lifetime.
Probably the most effective preservation technique is digitization. By scanning the negatives of a film, reconstructions have been done to produce 4k quality films, notably in 2006 with for the Blu-ray re-release of The Wizard of Oz. However, it is already too late for many films as an estimated 90% of all silent films and 50% of all sound films before 1950 have been lost. Therefore, it is more important than ever that the 25 films inducted into the National Film Registry each year are significant, so that we do not lose the films we love.
Probably the most effective preservation technique is digitization. By scanning the negatives of a film, reconstructions have been done to produce 4k quality films, notably in 2006 with for the Blu-ray re-release of The Wizard of Oz. However, it is already too late for many films as an estimated 90% of all silent films and 50% of all sound films before 1950 have been lost. Therefore, it is more important than ever that the 25 films inducted into the National Film Registry each year are significant, so that we do not lose the films we love.