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It can happen during a film screening when a frame becomes stuck in the projector's film gate. Acetate films are also subject to degradation over time. With exposure to heat, moisture, or acids, the acetyl groups are broken from their molecular bonds to the cellulose. The now free acetic acid is released into the air. Acetic acid is vinegar ...
Cellulose acetate is also known as "safety" film and started to replace nitrate film in still photography in the 1920s. [1] There are several types of acetate that were produced after 1925, which include diacetate (c. 1923 – c. 1955), acetate propionate (1927 – c. 1949), acetate butyrate (1936–present), and triacetate (c. 1950 – present). [1]
Cellulose diacetate film was first created by the German chemists Arthur Eichengrün and Theodore Becker, who patented it under the name Cellit, from a process they devised in 1901 for the direct acetylation of cellulose at a low temperature to prevent its degradation, which permitted the degree of acetylation to be controlled, thereby avoiding total conversion to its triacetate.
Cellulose acetate film, which was the initial replacement for nitrate, has been found to suffer from "vinegar syndrome". [14] Polyester film base, which replaced acetate, also suffers from fading colors. [5] Storage at carefully controlled low temperatures and low humidity can inhibit both color fading and the onset of vinegar syndrome.
Film has been made on a variety of materials, including nitrate-based film stock (see: Nitrocellulose) and acetate-based film stocks, and polyester-backed film. [8] Due to that difference, each of these film types have a different conservation strategy. [8] Nitrate film must be handled carefully, as it is highly flammable. [8]
Acetate films were replaced in the early 1980s by polyester film base materials which have been determined to be more stable than film stocks with a nitrate or acetate base. Color prints made on most inkjet printers look very good at first but they have a very short lifespan, measured in months rather than in years.
In general, decaying acetate film breaks down into acetic acid, and similar to celluloid decomposition, leads to an auto-catylictic breakdown of the base that cannot be reversed. The result of the acetic acid released is a strong odor of vinegar , which is why the decay process in the archival community is known as " vinegar syndrome ".
Photographic emulsion is a light-sensitive colloid used in film-based photography. Most commonly, in silver-gelatin photography, it consists of silver halide crystals dispersed in gelatin. The emulsion is usually coated onto a substrate of glass, films (of cellulose nitrate, cellulose acetate or polyester), paper, or fabric.