Posted by: preshist | May 18, 2012

VINEGAR SYNDROME IN NEGATIVES

This blog is an entry related to the Archives Month Theme of Scandalous Acts of Neglect

Myke Tymons who is contributing to the blog this week has recently commenced as Photographic Archivist after our previous Manager of Photographs, Donald Cochrane, left unexpectedly.  Myke found himself somewhat thrown into his new job of preserving the photographic collections and one of the early problems facing him was the issues of vingarisation of the negatives.  What’s that you ask?  Myke explains below.

Vinegar syndrome, or vinegarisation is a problem affecting photographic negatives, film strips and movie reels which were printed on `safety film’ between the 1920s through to the mid 1950s. The culprit has been identified as diacetate which was developed to replace the volatile and highly flammable cellulose nitrate based film of earlier years. The problem was discovered in the 1970s when Archives and Libraries started reporting a rapid deterioration of images in negative and film collections they held. Since that time most repositories for negatives and films made between 1922 and 1955 have reported vinegar syndrome damage in their collections.

Note the small white specks, particularly in the top left hand corner

Vinegar syndrome has been discovered to be caused by the diacetate degrading into acetic acid giving it a vinegary odour, hence its name. The damage it causes is a gradual (though not necessarily long) process which starts with the diacetate forming tiny pockets of acetic acid, which can not be seen by the naked eye. However there is slight warping of the negative on the edges.

A detail of the left hand corner where tiny pockets of acetic acid have formed

The next stage or level is when the vinegar smell develops which can be quite marked. As the smell gets stronger the next stage sees the pockets of acetic becoming larger and visible to the naked eye.

As the smell gets stronger the pockets of acetic become larger and visible to the naked eye.

It then becomes a process of join the dots as channels form due to the emulsion layer separating from the base. Once channels form copying from the negative produces distorted images. This channelling can continue until the negative is unviewable.

The emulsion layer separating from the base

There are a number of factors that affect the spread of vinegar syndrome and the speed with which it progresses. First and most important is the maintenance of proper temperature and humidity for the storage of the negatives. While estimates vary it is agreed that a low temperature/low humidity environment will help slow down the process. A humidity of 30% and a temperature of 10 Celsius is seen as an ideal environment. Although a lower temperature is acceptable (and possibly better) the negatives become brittle and susceptible to breaking. Estimates on the preservation life of negatives in the 30/10 environment range from 300 to 1000 years (!). The difficulty here is that the chillers needed for this kind of preservation are expensive and beyond the means of many archives (including ours). It should also be noted that geographical/meteorological factors can also play a part where warm muggy locations would be more susceptible than cooler dry areas (Indeed the syndrome first came to attention inIndiawhere it very hot and muggy).

Showing front side of negative above

Obviously, steps need to be taken before the negative gets to the channelling stage. One solution is to scan the negatives but with large collections this is time consuming and expensive. We have approximately 20,000 negatives, the bulk of them being from the Presbyterian Church’s now defunct Communications/Publicity Dept and scanning or duplicating them would be beyond our resources in time and money.  Early detection is vital as by the time the vinegar smell appears the process of degradation is well on its way. We have recently trialled Danchek 24 hour Acidity tester strips (available from Conservation Supplies) a type of litmus paper which can detect a change in the pH level of the negatives before a smell is discernable (between pH5 and 6) and it has enabled us to detect vinegar syndrome in sets of negatives where there was no smell.

Danchek 24 hour Acidity tester strips

Additionally it gives a visual reference to the levels of degradation and when the negative needs to be duplicated or scanned. If negatives with vinegarisation are found they need to be removed from the rest of the negatives as they can rapidly contaminate the rest.

Other means of reducing the risk of degradation are to put the negatives in acid free paper enclosures and restricting both air movement and humidity/temperature fluctuations. Acid in paper can set off or encourage the development of vinegar syndrome and we have nearly completed putting all our negatives into acid free enclosures. Recently we received a photo album that had negative strips contained in glassine envelopes within a larger brown paper envelope. After detecting a faint acidic odour we put a pH strip in each of the envelopes and in a couple of the glassine enclosures and left them overnight. On checking the strips the next morning, we found they indicated a pH level of 4.9 indicating that vinegarisation was present and increasing. On the basis of this we were able to prioritise them for scanning.

Changes in humidity and temperature can bring about rapid deterioration of the negatives as we recently discovered. Our negatives are in a large walk in safe set below ground level which maintains a generally constant low humidity/temperature level even with 2 hot water pipes running through the safe. This year we had a much warmer than usual summer and autumn and combined with the pipes the temperature rose quite quickly. I check the boxes containing the Department of Communication boxes once a week or so for a change in the Danchek strips and for any vinegar smell. They had had no odour or change in the strips since we started monitoring them. Within the space of a week with the raised temperature I noted to my alarm that two of the boxes had developed a smell and the strips indicated a change in pH from 5.5 (the start of degradation) to 4.8 which is just short of the autocatalytic stage (where the deterioration rate increases exponentially). The negatives were removed to another location until we were able to stabilise and reduce the temperature by relagging the pipes so much less heat escaped.

A negative that has been totally ‘attacked’ by the Vinegar Syndrome

In conclusion then, prevention is 90% of the cure so far as vinegar syndrome is concerned. Keeping the negatives in acid free enclosures in a constant low humidity/ low temperature environment is essential in reducing the chances of vinegar syndrome developing. There should be minimal airflow and negatives should be separated from each other in the enclosures. They should be checked regularly and often and if possible use Danchek strips to act as a warning system. If possible the negatives should be duplicated or scanned.

Modern film is not susceptible to vinegarisation and modern digital cameras mean that there is no film as such anyway. If vinegar syndrome is discovered, affected negatives should be removed from contact with the rest of the negatives. Without access to chillers with the correct humidity/ temperature scanning or duplication of the negatives is the only long term viable means of preserving the negatives.

by Myke Tymons

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