On the 11th of October myself and my colleague Barbara Taylor attended a training day entitled ‘Preserving historic photographs’ at the British Library Centre of Conservation. The day was run by Susie Clark, an ICON accredited photographic conservator, and was designed for those with responsibility for care of photographic collections regardless of institutional context. From a personal perspective, it was quite reassuring to realise that a lot of the history of photographic processes was still stored in my mind from over ten years ago when I did a BTEC National Diploma in photography before the BA degree here at Brighton.
The workshop started by running through steps of recognising different types of historic processes with samples for us to look at. Photographic materials deteriorate in a variety of ways depending on the original process. I found it especially interesting that during the 1950s, cellulose acetate was used widely in the manufacture of photographic film. The deterioration of this leads to the distinctive ‘vinegar syndrome’ – a very recognisable smell at which point the autocatalytic deterioration of the material is beginning.
Conservation issues are clearly different to standard paper conservation challenges due to the different metals and chemicals used in coating and sizing of photographic papers and negatives. Silver is the most commonly used metal in photography, but platinum and gold have also been used historically. Glass deterioration can also be observed in glass plate processes such as daguerrotypes, usually stored in glass cases creating their own microclimates, and wet collodion negatives. Interestingly cyanotypes are known to fade drastically when exposed to light for long periods of time, but their colour has been observed to come back when re-stored in the right conditions.
The workshop then ran through identifying suitable conservation treatments for the different types of materials. The most important consideration was highlighted to be preservation, ie. storage conditions. This is especially important in storing negatives and film containing cellulose nitrate, a highly volatile chemical which can catch fire on its own accord at a relatively low temperature of 38c. Recommended storage solutions for photographic materials are either pH neutral papers and boards with a high cotton and undetectable sulphur content or plastics, of which Melinex is the most commonly used as it has passed the Photographic Activity Test. Photographs should not be stored near a photocopy machine as these give out deteriorating ozones. Interestingly I did not realise that you can, and should in some cases, also freeze-store photographic materials by using sealed conservation quality polyethylene bags.
A fact I found rather wonderful was that already in 1855 a ‘Fading Committee’ was put together, supported by Prince Albert. Even after only a few decades of this wonderful medium, there was concern over its longevity!
If you are interested in further reading about preservation and conservation issues, The British Library Preservation Centre have published a series of preservation guidance booklets that can be downloaded free of charge. Included is the booklet on preservation of photographic materials written by Susie Clark.