Is the mothball smell naturally occurring with diacetate film?

[Daniel D. Teoli Jr.]

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• Does diacetate film naturally stink of mothballs as it ages? Or has the film just been stored in a humidor can with a preservative in it?

Examples of humidor film cans...





From what I gather, the humidor film can was used for added humidity via water and not chemicals. But maybe they used the humidor cans for both.





Photos: Daniel D. Teoli Jr. Archival Collection

Here is what AI says about the mothball smell...

Diacetate film, in the context of photographic and motion picture film, refers to a type of cellulose acetate base where two of the three hydroxyl groups on each glucose unit of the cellulose molecule have been replaced with acetyl groups. It was an early form of safety film, replacing the highly flammable nitrate film, and was used extensively in the early 20th century. Diacetate film is characterized by a characteristic smell of camphor or moth balls, and while it was a significant improvement over nitrate film, it did have some stability issues like shrinking and embrittlement, leading to its replacement by cellulose triacetate.
Key Characteristics and History:
Development:
Diacetate film was developed by chemists in the early 20th century as a less flammable alternative to nitrate film.
Chemical Composition:
It's a cellulose acetate polymer where two of the three possible sites on each glucose unit are acetylated, according to the National Film and Sound Archive of Australia.
Early Use:
It was used in both sheet and roll film, particularly for 16mm cinema films, as noted by the National Archives.
Limitations:
Diacetate film did suffer from issues like shrinking, embrittlement, and distortion, leading to its eventual replacement by cellulose triacetate.
"Vinegar Syndrome":
Like other cellulose acetates, diacetate film is susceptible to "vinegar syndrome," a condition where it deteriorates due to the release of acetic acid, resulting in a vinegar smell, shrinkage, brittleness, and the formation of crystals.

I'm thinking if the mothball smell is not a preservative, but a sign of deterioration; the reels need to be permanently aired out or at least stored in ventilated cans to de-gas. I have always kept them in non-ventilated metal cans thinking they were embalmed!

 

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[Robert Harris]

From my understanding, camphor was on the pads, and that kept the film pliable.

[Joerg Polzfusz]

Hi!

Back in the days, they put camphor into the cans, too, not only into the humidor cans. Hence, for an amateur, it’s hard to say whether the film is decomposing or whether it was stored with camphor.

https://www.nfsa.gov.au/preservation/preservation-glossary/decomposition says:

„… Diacetate base film was used between the early 1920’s and 1951. Triacetate base had become a commercial proposition after World War II. Diacetate was based on a chemical constituent of camphor, and when this material degenerates it gives off a smell characteristic of camphor or napthalene. Another indication of its degeneration is brittleness. …“

https://www.paulivester.com/films/preserve.htm says:

„…The earlier diacetate film (before the mid 1940s) might be slightly less prone to vinegar syndrome, but often emits a camphor or "mothball" smell due to the plasticizers used.  Agfa-Gevaert stock emits a peculiar odor, which should not be confused with vinegar syndrome.…“

 

Edited April 29 by Joerg Polzfusz

[Daniel D. Teoli Jr.]

Thanks for the replies!