If we don’t have any information implying the kind of base we are dealing with, or our film was copied on numerous occasions and the film stock features several contradictory marks, we are obliged to carry out tests in order to unambiguously determine the type of base.
- immersion tests
During an immersion test, we identify film produced on nitrocellulose, acetate cellulose and polyester base. To carry out the test we need a sample of a minimal length of 6 mm. Having immersed the sample in trichloroethylene we can observe that in the case of NITRATE base the sample is subject to total immersion and sinks to the bottom of the recipient, whereas in the case of ACETATE base the sample flows on the surface, while polyester film flows in the middle of the solution’s height. When carrying out the test, it is necessary to take into account the degree of damage to ACETATE materials because in the case of a very damaged film, after immersing in trichloroethylene it can be subject to total immersion like nitrocellulose.
- diphenylamine test
The purpose of the test is to identify NITRATE base. It uses concentrated sulphuric acid and 5 g of diphenylamine. After placing two drops of solution on the film base and waiting for 60 seconds, the solution will turn blue in the case of nitrocellulose.
diphenylamine test, phot. Monika Supruniuk
- combustion test
Similarly to the diphenylamine test, combustion test enables us to recognize nitrocellulose. Having cut off a snippet of stock, we can try setting it aflame. If the film burns dynamically, it means that we are dealing with nitrocellulose.
