Before any film is copied it is vital that it be made as clean as possible. It may be impossible to get film completely clean, since some particles of foreign matter can become so embedded into the surfaces of the film that it is not practicable to remove them. As well as solid particles, film can have oil, grease or wax on surfaces.
Cleaning is carried out using a solvent of these substances, which also serves to carry away particles of dirt. There are several solvents which can be used. The one most commonly used is trichloroethane in an inhibited version. Apart from some proprietary and more expensive preparations, this is the least toxic of the effective solvents. Two warnings are needed:
1. All of these volatile cleaning agents are toxic, and good ventilation must be provided whenever they are used. Beware of using carbon tetrachloride. This is extremely toxic, so much so that its use is banned in many countries.
2. Beware of any temptation to use an flammable agent like petrol or methylated spirits.
Cleaning can be carried out by hand or by machine. If it is available, and the condition of the film permits it, machine cleaning by a suitable machine is more satisfactory than hand cleaning.
At the NFSA hand cleaning is only performed using isopropyl alcohol and D-Limonene (a citrus based cleaner). Typically for cleaning small spots or sections of dirt, oil and adhesive from tape. Also commonly used to test whether a blemish is oil or ferrotyping.