The preservation of audiovisual materials is a labour intensive and time consuming activity. The majority of our audiovisual records are 35mm and 16mm film, audio tape, video tape, and digital video.
In 2014, building began on an archival film laboratory which started production in May 2015 whereby our NFU film collection is being preserved by copying the original acetate or nitrate based original film elements to modern polyester film stock. Polyester is an extremely stable plastic which has a projected life of 500+ years. Producing such film copies ensures their long-term survival, and financially compares favourably to the costs of preservation-level digitisation.
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Pre-1951 motion picture film was produced using cellulose nitrate film. Nitrate film needs to be stored in special conditions and copied onto newer film stock to prolong its life. If stored in bad conditions it can decompose to a point where the image and sound can no longer be recovered. Archives New Zealand has over 2000 cans of nitrate film.
In the early 1950s, nitrate film was replaced with cellulose acetate. Although acetate film proved to be less flammable than nitrate film, it also suffers from decomposition. When acetate film decomposes, it gives off strong acetic acid (vinegar) gases, giving this phenomenon the common name ‘vinegar syndrome’. The gases given off by decomposing film can also incite decomposition in other films, and so have to be separated from the rest of the collection.
Both nitrate and acetate decomposition effect the base of the film, but another issue which affects motion picture film is the fading of the image element itself. This is most often seen in the picture turning red as the colour dyes in the film’s emulsion break down. As the colour fading increases, it becomes harder and harder to correct that colour shift either photochemically or by digital means.
Analogue audio material is recorded onto magnetic tape, a medium whose life expectancy can be measured in decades. Because of the inevitable degradation of the magnetic carrier, our preservation programme for audio material involves not just appropriate storage, but also preservation-quality digitization of this material. Audio collections represent the majority of magnetic material held at Archives New Zealand, and include different formats such as 16mm and 35mm magnetic track, open reel audio tape, and audio cassette tapes.
Videotape was first used in television production in the 1950s. Like film, the physical magnetic tape is susceptible to decomposition, and the audiovisual information contained on the tape is susceptible to damage (sticky shed syndrome or binder deterioriation, etc) and information loss. What also makes video difficult to preserve is the increasing difficulty in sourcing relevant playback devices: older video machines are hard to find and to maintain, and there are also multiple formats and systems, some of which were used widely and others which were only used for small periods of time or by specific organisations. Archives New Zealand holds video in a range of formats, including U-matic (3/4”), 1”, 2”, and VHS, as well as digital video formats such as DVCAM and MiniDV.
Because of the short life of magnetic media (i.e., video and audio tapes), digitisation of that material is key to its long-term preservation, survival, and access. Digitisation of our magnetic media is carried out at the highest possible quality in accordance with international standards.
To ensure that all of our audiovisual holdings are preserved and ensure their long term survival and access, we store all of our audiovisual material in conditions that delay decomposition and fading.