Problems with preserving coloured films
The preservation of coloured nitrate film presents a number of physical and technical challenges. The chemical composition of early cellulose nitrate film means that it burns easily, is extremely difficult to extinguish, and gives off highly toxic smoke.12 In fact, one of the original uses of cellulose nitrate was as an explosive known as gun cotton. Because of its volatility, the use and handling of cellulose nitrate film is governed by strict occupational health and safety regulations and only a limited number of places (film archives and specialist film restoration companies) are able to receive and work with this material. Some of the original dyes can also be flammable, highly toxic, or potentially explosive (Sir William Henry Perkin, the inventor of the first coal-based aniline dye, Mauveine, blew up two factories).13 Apart from the difficulties in handling nitrate safely (without causing damage to the film or the film technician), there are a number of factors that make it difficult to create an accurate copy of a film’s coloured image.
The production of nitrate film stopped in the early 1950s, meaning that the nitrate-based material held at the NFSA is at least 60 years old and some of our films are over 100 years old. As nitrate ages it shrinks and buckles, becomes brittle, and chemically decays. Sadly, this decay cannot be stopped, though it can be slowed with appropriate storage conditions.
Making a new copy is the only way to ensure the future survival of the content of the material. However, as nitrate decays, the film’s colour fades and may even change hue completely over time (making it extremely difficult to tell what the original colour might have been). The type of dye or toner used to colour the image may increase its rate of decomposition.
Worse still, the colour may not decay evenly across the film and this produces a mottled look. This mottling is reproduced in any copies made of the film and is extremely difficult to remove.
Tinting and toning were applied as the last part of the process (to the cinema release print) and the surviving films have usually been projected multiple times. This means that the films have also suffered physical damage such as broken perforations, scratches and breaks. Due to its fragility, nitrate material can only be copied using specialised film equipment that has been modified to deal with problems like film shrinkage.