Exploring

Inherent Vice: Film Supports

Nitrate Film

Nitrate film was invented in the late 19th century in response to the need for a more lightweight and less fragile support for photographic negatives. The first nitrate sheet film negatives were made from celluloid (an primitive form of plastic made from cellulose nitrate combined with a plasticizer). Celluloid was first created in 1846 and was used for many purposes, including making billiard balls and combs. In 1887, the first sheet film negatives were made by coating a thick sheet of celluloid with a layer of gelatin emulsion. Within a few years, gelatin emulsion roll film made from a thinner and more flexible form of celluloid became available.

Cellulose nitrate film was used as the support for many different types of film, including portrait and commercial sheet film, x-ray film, 35mm roll film, and motion picture film. It was not used for color film or for 16mm or 8mm film (both of which were made for the home and educational markets). Nitrate film was eventually supplanted by cellulose acetate film, and the Eastman Kodak Company stopped producing nitrate film completely in 1951.

Characteristic Types of Deterioration

Nitrate film is extremely flammable, which eventually led to its discontinuation and replacement by cellulose acetate film. Its chemical instability was less apparent at first, but six progressive stages of its deterioration have been extensively documented over the years:

1. No deterioration.
2. The film turns yellow and the image exhibits silver mirroring.
3. The film becomes sticky and gives off a strong nitric acid odor.
4. The film turns an amber color and the silver image begins to fade.
5. The film becomes soft and may adhere to adjacent materials, and the image becomes illegible. see
6. The film breaks down completely, turning into a brown powder.

The chemical decay of nitrate film is irreversible and is made worse by high temperature and high relative humidity. Duplication onto stable film and cold storage of originals is recommended.

Identifying Nitrate Film

If film exhibits the characteristic forms of deterioration described above, it can be easily identified as nitrate film. Nitrate film can sometimes be identified by date (e.g., almost all film manufactured between 1889 and 1920 was nitrate), but detailed date information is not always available. Other means of identifying nitrate film include:

• Edge Printing—located on the edge of the film is the name or type of film base, such as "NITRATE"; the name of the manufacturer; and/or notch codes, which were notches of various shapes meant to identify the type and the emulsion side of the film)
• Curling—early nitrate roll films tend to curl very tightly; in 1903, manufacturers began to coat the reverse side of the film with gelatin to prevent this problem
• Destructive Tests—procedures such as the diphenylamine test, floatation test, or burn test can be performed; these destroy the material being tested and should be performed only by a professional.