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UW Madison: Wisconsin nitrate film project


A University of Wisconsin-Madison group has just published results from a six-year exploration of old, unstable film stock that nevertheless holds the oldest heritage of moving pictures.

Called "nitrate film," it's flammable and fragile. Many films shot a century ago are largely transparent, or clumped and unable to be seen, let alone projected.

The Wisconsin Nitrate Film Project at the Wisconsin Center for Film and Theater Research was the brainchild of Heather Heckman, then a communication arts graduate student in Madison. Heckman, who now directs the Moving Image Research Collections at the University of South Carolina, wanted to address nitrate film from multiple directions, and so the effort combined chemical analysis of the film, review of historical literature on it, and information from professionals who have handled, stored and shipped nitrate film.

Cellulose nitrate film stock was introduced in the late 1800s as a medium to hold the emulsion that carries a photographic image.

"Film had to be transparent and flexible enough to run through the camera and projectors," says Smith, "and this engineering problem was solved by invention of cellulose nitrate. At first, people did not think about it being highly flammable, but the word got around that the brown powder it formed after it degraded was especially combustible. Our tests, on a small sample, showed the powder to be non-hazardous, but more tests are needed."

The phase-out of nitrate film in favor of "safety film" started in the 1930s, and Eastman Kodak "retired" nitrate film by 1952. Many older films have been transferred to modern film stock, but the remaining nitrate film amounts to "a whole visual heritage," Smith says. "If you look at the silent movies, the rate of survival is around 20 percent. Preserving what we have left is important, because the losses have been massive."

The nitrate project was needed, Smith says, "because we did not know what happens at a very basic chemical level."

The project's researchers based their recommendations on tests of surplus nitrate stock.

"The big finding was to keep it dry," Smith says. "Humidity is one of the most important factors to control, and temperature comes second."

Beyond the science, the project also created an oral history from people experienced in handling nitrate stock. "These were long-form interviews of projectionists, preservationists and people who worked in photo labs," says Smith. "There has been lore that nitrate would spontaneously combust, but we heard that nitrate was to be respected but not feared. It needs to be handled with care, but it's not going to explode. It's not nitroglycerin," even though cellulose nitrate is a close relative of guncotton and other flammables.

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