Preserving nitrate and acetate film collections

film-1331184_640Owners of Acetate- or Nitrate-based motion picture film collections have few good options for restoring and preserving those assets. Although Nitrate and Acetate-based film stocks are chemically different from each other, they are both highly susceptible to degradation, as well as combustion in the case of Nitrate, and should be given priority attention, before it becomes impossible to save valuable, irreplaceable content.

If there’s anything as rare as old Nitrate and Acetate films, it’s the people and facilities available to do a proper job of restoring and preserving them. That’s one of the reasons LAC Group acquired PRO-TEK in 2013, one of the top providers of film inspection, restoration and preservation services. As a business that was founded by Kodak itself, LAC Group gained not only a specialized film vault, but proprietary processes and dedicated film experts. Combined, the skills, experience and physical assets are virtually unmatched in the motion picture industry.

Two materials were primarily used in the manufacturing process of motion picture film– cellulose Nitrate and cellulose Acetate. Nitrate-based film stocks went by many names, including; nitrocellulose and celluloid, while cellulose Acetate film has often been referred to as ‘Safety’ film. A third material, Polyester, has also been used for many years.

Nitrate Film Considerations

The first film stocks, used from the late 1800s until the early 1950s, were Nitrate-based. Nitrate produced stunning variations of light and shadow with a kind of fluidity that has never been replicated. Unfortunately, Nitrate is subject to decomposition –

  • Factors like heat and humidity can cause the film to shrink.
  • As it breaks down, it gives off gases that cause yellowing, softening and oxidization.
  • These gases are toxic, oxidizing agents with the power to escape film storage cans and attack any nearby Acetate or polyester film.

Most dangerously, Nitrate is a highly combustible compound that supplies its own oxygen as it burns. Once ignited, Nitrate film must burn itself out, as it cannot be extinguished. Fires in the projection booths of early movie theaters were not uncommon, as well as in other institutions and storage facilities, including tragedies that resulted in multiple deaths. Aware of the early movie-going audience’s fear of fire, manufacturers began developing Acetate-based ‘Safety Film’ as far back as the early 1900’s, but commercial 35mm film remained primarily Nitrate until 1951. In the home and hobby market, however, Acetate begins replacing Nitrate by 1912. It would be another 40 years before 35mm film finally leaves Nitrate behind.

More on Nitrate Film Stock.

How to Determine if Film is Nitrate-Based

  • Age – The use of Nitrate in film manufacturing was discontinued in the early 1950s. If your film is 35mm and was shot before then, it’s probably Nitrate. After that, it’s likely Acetate, though not necessarily.
  • Outward Appearance – Film may have a slight brown powder residue, or leave faint rust marks on the can. This is a sign of oxidizing gasses escaping. Film may be sticky or have slight bubbles or foam appearing.
  • Smell – Nitrate can have an acrid, almost corrosive smell.
  • Examining the edges of the film – Film may have the word ‘Nitrate’ printed on it or if there are no printed markings on the edges, it is most likely Nitrate. If the word ‘safety’ is printed, it’s not Nitrate.
  • Lab Testing – In addition, laboratory tests can be done to determine a film’s composition.

As a hazardous material, strict laws apply to the projection, storage and shipping of Nitrate film. In fact, only professional film archivists should handle it. In addition, only authorized persons or institutions can ship or transport Nitrate film. Studies have shown that with specialized handling and storage, Nitrate base films can be preserved for extended period of time.

Acetate Film Considerations

Acetate was the material that replaced Nitrate, and it’s more commonly known as safety film because it does not possess Nitrate’s combustible characteristics. Cellulose diAcetate or triAcetate film is, however, prone to something called vinegar syndrome. If not properly handled, Acetate film can undergo the process of de-acetylation, which forms acetic acid that causes a vinegar-like smell when the film can is opened. It’s important to know that once this reaction begins, it cannot be stopped, leading to ongoing deterioration.

Moisture, temperature, acids and other chemical and environmental factors are known to decrease the life expectancy of Acetate film. Acetate film can also buckle and warp.

But in some cases, proper care and technique can halt or slow deterioration. Vinegar-syndrome can be contained or slowed with special storage using unique chemical agents. The gasses can be trapped into material that isolates it from the rest of the film and surrounding elements. This material containing trapped gasses can be monitored closely and discarded and replaced as needed.

Motion Picture Film Restoration and Preservation Considerations

Film vaults that are calibrated and monitored to maintain ideal temperature and humidity are a must. Yet it makes no sense to store bad film in a good vault – it’s crucial that all film be thoroughly inspected first. With the right people and processes, repair and restoration can be an option.

Along with inspection and restoration of the original film, copies of quality motion picture film should be made. Archiving standards call for the creation of a new film copy (photochemical preservation) for preservation purposes. It may seem unlikely, but properly stored film will last longer than digital files. You may ask for a preservation copy for long-term storage, which is a high quality duplicate that can take the place of original film that deteriorates beyond use. You may also request an access copy in one or more well-supported formats if you want easy, short-term availability and use.

Finally, if the collection is extensive, you may request how you want the files to be organized and to include metadata. Metadata is essentially data about the data, and might incorporate information like a title, date and description of the content.

To learn more about Nitrate and Acetate (Safety) film archiving and preservation, see the following articles:

Nitrate Film: If It Hasn’t Gone Away, It’s Still Here!

Acetate (Safety) Film and Nitrate Film Don’t Mix – Or Do They?

In addition, learn more by clicking on any of the following links to the U.S. National Archives, Association of Moving Image Archivists (AMIA) and Kodak websites.

http://www.archives.gov/preservation/formats/motion-picture-film-toc.html

http://www.amianet.org/groups/committees/Nitrate/documents/NitrateIGNov08.pdf

http://motion.kodak.com/motion/Support/Technical_Information/index.htm

Tim Knapp

Tim Knapp

Tim Knapp is the Vice President of Client Engagement for PRO-TEK Vaults at the Burbank and Thousand Oaks location. Tim brings more than thirty years of experience in motion and still imaging – first in film, and most recently in digital. Tim has an extensive and wide-ranging understanding of the capabilities and challenges of film and video, including the issues and opportunities it presents for archivists as they face aging media libraries and an increasingly digital future.
Tim Knapp