The American Heritage Center is home to nearly 90,000 cubic feet of historically significant collection material, representing centuries of cultural heritage within a wide range of subject matter. Whether it be a paper document, work of art, three-dimensional artifact, analog photograph, born digital media, or something else, collection material in any format presents unique challenges to archival preservation. Among the most troublesome of formats is nitrate film.

Cellulose nitrate-based films were produced from the late 19^th century until 1952. Nitrate was the first flexible film base, developed to replace glass plate negatives, and was widely used for photographic film negatives, motion picture film reels, and medical X-rays. Though its invention marked a significant step in the evolution of photography, its risk quickly became apparent, as nitrate film is highly unstable and prone to combustion at as low as 104°F. Once ignited, nitrate film burns hot and fast, off-gassing oxygen and poisonous gases, fueling its own fire and making it extremely difficult to extinguish. Nitrate has even been known to explode or burn underwater. To address the risk of catastrophic fires in darkrooms, movie theaters, and hospitals as a direct result of nitrate film, cellulose acetate film was developed in the early 20^th century and marketed as “Safety Film,” eventually replacing nitrate as a safer alternative.

Nitrate film can be kept safely in a cold storage vault, which protects the negatives from fire and significantly slows its deterioration. Over time, nitrate film will turn yellow and brittle, release harmful fumes of nitric acid, and the emulsion on the negative will decompose into a flammable powder, by which time the photographic content is lost forever. Acetate, or safety film, is not flammable like nitrate but does also deteriorate over time, so it is often kept in cold storage as well.

One of the ongoing projects within the AHC’s Photographic Lab seeks to address these preservation issues. We start by pulling a box of negatives from the Cold Vault and appraise each negative individually, identifying its photographic content, condition, and level of deterioration. The next step of the project is to digitize each negative in order to preserve the historic content while allowing us to dispose of the original negatives as hazardous materials. Because our intention is to dispose of the originals, it is crucial that we digitize them to an extremely high quality. As recommended by federal archival guidelines, the AHC recently obtained a 100 MP digital camera which will allow us to digitize these film negatives in accordance with the highest current archival standard. This investment has significantly increased our ability to deal with the preservation issues previously outlined, with the additional benefit of making the photographs more accessible to our patrons.

In the past two years, the AHC’s Photographic Lab has individually appraised 2,006 nitrate and acetate negatives across 12 collections. So far in 2021, we have digitized 393 of these negatives to preservation quality using the new camera. The subject matter of these negatives include University of Wyoming botany class field trips led by Dr. Aven Nelson in 1919, a Cheyenne Frontier Days rodeo held approximately a century ago, landscapes and portraits taken in the Himalayan Region in the 1920s-1930s, the aftermath of the Holliday fire which destroyed several blocks of downtown Laramie in 1948, and various other scenes illustrating life in Laramie and the surrounding communities in the 1910s-1950s.

The issues surrounding nitrate and acetate film are quite vexing, but the American Heritage Center is committed to preserving our share of photographic history for generations to come. The recent advancements of our digitization capabilities are exciting, and we are looking forward to sharing more of these photographs as the project progresses.

Post contributed by AHC Archives Specialist Hanna Fox.

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