Identification / non-destructive tests

Identification of film base begins with an examination of film properties. In the first place, we should focus on such aspects as:

• edges of the film

Some producers placed information on the type of base on the edges of the film. On the NITRATE base we could come across: “nitrate”, “Kodak Nitrate Film”, whereas on the non-inflammable ACETATE base the most often inscription was: “S”, “safety” and “sicher”. It’s worth remembering that the film on a safe base could be duplicated e.g. from a NITRATE negative, and despite the inscription “nitrate” (in this case in white) we are not dealing with an easily inflammable base.

As of 1916, Eastman Kodak started placing geometric codes to inform about the date of production of the material. The characteristics of date coding are available at http://www.film-center.com/dates.html, among others.

AGFA changed the font of the name placed along the edge of the film stock, using since 1924 the typeface in bold.

Cud Nad Wisłą (1921)								Mogiła Nieznanego Żołnierza (1927), fot. Monika Supruniuk

• audiovisual information

It is often the case that on the basis of audiovisual information included in the film we can recognise the time when it was produced. It is assumed that until ca. 1952 film materials in the 35 mm format were produced exclusively on nitrocellulose base.

• characteristic damages

The degree of damage to the base produced on the basis of nitrocellulose can be determined on a five-degree scale. During decomposition, NITRATE film gives out gases of a characteristic nitric smell. Base becomes yellow, sometimes sticky. The image recorded in the emulsion layer fades. The colour of film stock changes with a simultaneous decrease in the mechanical resistance of the film. Similar symptoms of degradation can be observed on films with safe base (cellulose di- or triacetate). In this case, released gases give out a smell that is similar to that of vinegar.