In a recent search for other images I came across this. Tom Heitman, director of preservation and restoration at Cineric, Inc., showed me this can on a visit to the facility on May 20, 2002.
This film has sections of cellulose triacetate film spliced with sections of nitrate film, both unstable materials in their own way. Nitrate film is flammable and dangerous to handle. Acetate films degrade slowly over time. It’s interesting that in this case it’s the newer acetate film that has degraded and is taking the nitrate along with it. The acetate sections exhibit vinegar syndrome, the film degrades and releases gases that smell like vinegar, thus the name. The danger is the reaction is autocatalytic and therefore contagious between film reels.
Film archives inspect their films regularly for signs of vinegar syndrome. It can be retarted through storage in vented cans in cool and dry conditions and the use of molecular sieves, special filters that absorb the gasses being released. Films that exhibit signs of vinegar syndrome are quarantined and copied onto a new piece of film. In this case, the nitrate sections were almost impossible to salvage, the acetate sections were totally lost. Many films of historical value have been lost in this manner. Contemporary film stock is made with a polyester base that can last over 100 years under proper storage conditions.