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This Technical Bulletin provides a comprehensive look at photographic negatives on plastic film bases made up of cellulose nitrate, cellulose acetate and polyester, and covers issues related to material composition, mechanisms of deterioration, access, handling and storage.
16 sty 2018 · Nitrate negatives usually deteriorate in just a few decades, making them an extremely unstable storage medium. As they deteriorate, the image begins to fade and the negative turns soft and gooey, causing it to weld itself to whatever it’s stored with, resulting in the loss of the image.
cellulose nitrate negative from the 1890's or a cellulose triacetate color transparency from the 1990's, share very similar deterioration mechanisms that are temperature and humidity dependent.
Deteriorated nitrate negatives are easy to identify, but nitrate negatives in good condition are almost visually indistinguishable from other types of transparent films. There are four ways to identify nitrate negatives.
Photographic negatives are made of an image-forming substance or emulsion, which is coated onto a base or support. The bases found in the Genthe collection are either glass, nitrate film (nitrocellulose), or safety film (cellulose acetate).
Film-based photographic collections of nitrate negatives pose major challenges to preservation and access because of unstable media and the lack of item-level indexing.
A negative is basically image-forming light sensitive salts (colour negatives incorporate dyes) suspended in a binder or emulsion of collodion, albumen or gelatin which is carried on a paper, glass or film support. The negative image is generated in a camera and the positive print is produced through either the 1:1 contact process or enlargement.
