The Departure of the Second Contingent for the Boer War was filmed on cellulose nitrate film. A type of professional film stock, nitrate was common from the invention of photographic film, through to the 1950s.

	Only small sections of director Rudall Hayward’s 1925 film Rewi's Last Stand survive today. The images on this page illustrate the fragile nature of nitrate film.

The film was popular with professional filmmakers because its high silver content created very luminous black and white images. It also wore well, making it suitable for repeated theatrical screenings. While other smaller film stocks were developed for parlour or home use, none had the rich tones and physical strength of nitrate film. For many decades, therefore, nitrate was the preferred choice for those who made commercial films.

Despite its popularity, however, nitrate film has always been chemically unstable. Not only does it decompose easily under adverse conditions, but it is also highly flammable.

Beautiful but deadly

Nitrate film burns 20 times as fast as wood, can reach burning temperatures of up to 1700 degrees Celsius, and contains enough oxygen to continue burning under water. Since its invention, nitrate has been responsible for a number of fires and fatalities. In Paris, in May 1897, nitrate film passing through a projector caught alight, and the ensuing fire caused the deaths of 180 people. In July 1980, in Kristiansand, Norway, an explosion in a theatre severely injured nine people. Originally thought to be a bomb, the cause was discovered to be the spontaneous combustion of a collection of nitrate films stored in the theatre’s attic.

Rewi's Last Stand, 1925

To overcome this obvious danger, film manufacturers developed safety films, made with cellulose acetate. These were successfully introduced for non-professional gauges, such as 16mm, but it took many decades before a professional film was developed that was not only safe, but also produced wonderful images. In 1949, the Eastman Kodak Company introduced a high quality acetate-based 35mm stock that gained acceptance among film professionals and soon after, nitrate film production ceased. No films are made on nitrate stock today.

Nitrate Won’t Wait!

The loss of precious films to fire is only one reason why the New Zealand Film Archive is eager to collect and preserve nitrate film. Nitrate, like all film, is susceptible to decomposition, meaning that images of our past are at risk of disappearing.

	Rewi's Last Stand, 1925

All film consists of an emulsion laid on a transparent base. The emulsion is made of layers of gelatin containing light-sensitive materials, which capture an image when exposed to light. As nitrate film decomposes, it releases nitrous gasses, which in turn combine with water in the gelatin and surrounding air to form nitrous acid and nitric acid. These acids bleach the emulsion and cause the base to break down, to the point of total destruction. As the film decomposes, it first becomes sticky, then congeals together, before finally disintegrating to powder.

While some 100-year-old nitrate films have survived well, poorly stored nitrate have known to decompose completely within a matter of years. Without preservation, important historical records can be irretrievably lost.

Caring for nitrate

Locating and preserving at-risk nitrate film like The Departure of the Second Contingent for the Boer War is only a small part of the process for Archive staff. With such volatile material, shipping, handling, and storage are also very important.

When a member of the public offers a film to the Archive for deposit, one of the first things staff must do is ascertain whether the film is likely to be nitrate. This is crucial because, while most films can be transported safely, nitrate must be handled and transported with extreme care. For nitrate film, a metal case, labelled ‘flammable solid’, is dispatched to the depositor for transport of the film. A Dangerous Goods Declaration is also prepared in accordance with New Zealand law.

When nitrate film arrives in Wellington, staff attend to it immediately. Once the film has been assessed, and its details entered into the database, it is allocated permanent storage. Nitrate’s flammable nature means that all nitrate films are handled and stored well away from the main Archive collection, at an old ammunition bunker. Built of brick, the windowless bunker is dry and cool, ensuring the films are stored safely.

Caring for nitrate films is an ongoing task. Decomposition means that films can become sticky, potentially lifting the picture image from the base. Nitrate films can also build up a large amount of nitrous fumes inside their storage cans. To alleviate these problems, and to allow staff a regular opportunity to check the films, an annual ‘wind through’ is held. The wind through involves hand winding every nitrate film from spool to spool, while listening and watching for evidence of stickiness.

Nitrate films almost certainly become more fragile as they grow older. To ensure images are not lost altogether, at-risk films are copied onto a stable alternative, such as safety film stock. This ensures that even when a film does not survive, the images will live on.

Any member of the public who thinks they may have nitrate film is encouraged to contact the Archive. For more information on supporting the Archive’s film preservation work, read about the Rosier Fund.