Cellulose acetate negative
Dates of major use: 1925-1950
Inventor: Film manufacturers
Cellulose acetate film was used as a safe replacement for the unstable and highly flammable cellulose nitrate film.
There are three methods to identify negatives: by inspecting edge printing and notch codes for dating information, by looking for acetate film-based deterioration and by testing the materials.
The edge printing on this negative is obvious, as the word "safety KODAK" is labeled on the emulsion side of the upper right edge of the negative border. There are also two V- and two U-shaped notch codes, which correspond to Kodak 14B safety negative sheet film.
As for dating the material, cellulose diacetate sheet film was used from 1925-1950 and cellulose acetate propionate was in production from 1930-1945. We also know the provenance of this negative of Sir Winston Churchill, which was taken by Yousuf Karsh on December 1941.
Therefore, we can accurately say that this negative is made with cellulose acetate.