The familiar plastic-based photographic negatives and slides we all know and use are a relatively recent development. Kodak introduced the first cellulose nitrate film sheet in 1903 and experimentation with different types of acetate and cellulose compounds continued to 1960 when the polyester film support now used was introduced.
Prior to this, from about 1851, photographic emulsions were made on glass supports. Sizes ranged from large whole plate (6 1/2 " x 8 1/2") to the small quarter plate (3 1/4 x 4 1/4") although there were larger and smaller plates over the years. The very early negatives were made on the spot by pouring the emulsion layer on to the glass, allowing it to dry and then exposing it. By the turn of the century, though, the coated glass plates were being made in factories and bought by the boxful, much like photographic paper is bought today. The use of glass plates continued up to the 1920s.
The Library has more than 30,000 glass negatives in its photographic collections, assembled from both acquired and donated materials. Many well known Australian photographers such as Harold Cazneaux, Frank Hurley and R.C. Strangman are included and some of the collections like Tilba Tilba, Mildenhall, Mandurama and Collingridge form a great part of the Library's Pictorial reference collection.
Because of the nature of both the photographic emulsions and the glass, storage conditions are very important in preserving the images on these glass negatives. Glass tends to become brittle as it ages and is very easily shattered or broken. The different types of emulsion layer vary but all may suffer from extremes of heat and humidity. Also, the glass plate does not expand or contract as the emulsions do, resulting in cracking, blistering and lifting. If left unattended, the image in this emulsion layer can be lost forever. The majority of the Library's glass negatives are in fairly good shape, however storage conditions have not always been the best. Many of the negatives are still in the original packaging materials such as acidic cardboard boxes and glassine envelopes with many exhibiting the natural problems of aged materials including breakages, losses and dirt. In 1989 Preservation and Pictorial devised a program of rehousing the collections and keeping them in the new purpose built Coldstore.
The most important aspect of glass negative preservation is to ensure the image is retained and made accessible. Thus, wherever possible, the first step is to make a copy of the negative images on to polyester based black and white and colour transparency films. In some cases it has been more practical to rehouse the negatives before copying the images so they can be copied at a later date when time and staff permit. These copies are produced by NLA Photographics and are distributed for use in Pictorial Reference with master copies housed in the Coldstore.
Staff in Preservation then remove the glass negative from its old storage wrappings or boxes. A condition check is made and repairs to stabilise damaged or broken negatives are done where necessary. Each glass negative is individually wrapped in acid free non-buffered paper before being placed in acid free, high quality storage boxes. Original inscriptions on wrappings or boxes are recorded or retained and Pictorial accession numbers are included with the negative. These boxed negatives are then kept in the Coldstore at a constant conditions of 8C and 35% RH. The glass negative is then only retrieved if the copy masters are lost or destroyed.
The final phase of the rehousing procedure is to enter the accession and cataloguing details of the negatives into Preservation Services' online Coldstore Management System. This provides instant location and condition information in case retrieval of any negative is required.
The project has re-housed approximately two thirds of the glass negative collection to date.
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