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The Conservation of Photographs on Film
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Vinegar Syndrome I'm often surprised at how little thought we photographers give to the long term survival of our negatives. We assume that they'll be around long after we've gone and become some kind of legacy at least for our children if not the wider society. Unfortunately, most of our negatives and transparencies will barely outlive us and if we live a normal life span we will see many of them become unusable. The reason is an ageing disease of film known as "Vinegar Syndrome". We've all heard of early nitrate films becoming unstable and either catching fire or crumbling to dust. The film that was introduced to eliminate these problems was known as "safety film" and it was made of cellulose acetate. It was thought to be stable and most film since then has been made of this type of plastic. Unfortunately, we've since learned that it's far from stable and will break down, releasing acetic acid, which smells like vinegar. This is a serious issue for all of us but especially for those who are responsible for large collections of images such as image libraries and archives. There are a number of problems that can threaten our images on film such as fungal attack, poor processing that leaves residual chemicals and dye instability, but the one now being faced by institutions world wide is vinegar syndrome. Even though it's been known about for some time its only recently that the great boom in photography that took place during the 1960s and 70s has resulted in large numbers of images being affected. It takes up to 30 years after a photograph was taken for it to start to break down and we are now at the point where this has become a serious problem. What can be done to save our negatives and transparencies? My early studies in industrial chemistry have given me a special interest in this area and I'm currently working on a major Queensland Government collection of negatives from the 1950s to 70s with the aim of mitigating the effects of vinegar syndrome. I should point out here that the onset of vinegar syndrome can be delayed but once it begins there's nothing we can do to reverse the process, Humidity controlled cold storage is the only way of slowing its effects. Firstly, it's important to recognise the early stages of the disease and in this I strongly recommend the purchase of acid detecting strips which can be placed with film images and change colour in the presence of acetic acid. This will usually be the first sign and will be followed by an increasing smell of vinegar. At this stage there will be no visible signs that anything's wrong except that the film may no longer sit flat. Small bubbles soon begin to appear, usually under the films' anti-curl layer if it has one.
The bubbles will spread out and form channels and the film will start to curl, first near the edges, as the base shrinks.
Even at this stage the emulsion of the film may not be damaged and can sometimes be removed from the film and transferred to another support. This is a difficult and delicate process that should not be attempted without experience as the emulsion can easily be damaged.
As the film base shrinks with the loss of the plasticiser, channels and bubbles appear in the emulsion as well.
Eventually the film base will become brittle.
Sometimes a blue or pink colour appears in the film. This is caused by the return of the anti-halation dye which is made colourless by the alkaline developer during processing but reappears as the acetic acid concentration increases. Larger bubbles containing wet acid can also form.
Obviously, to rescue the image at this stage is very difficult if not impossible. It's far preferable to act long before it gets to this but it's not always easy to assess how long the onset and progress of the disease will take. It depends on a number of factors, the main one being storage conditions. People who live in a cold and dry climate will probably not experience this problem with their film images because the disease is triggered by humidity and heat in that order. Film stored without air conditioning in tropical areas is particularly at risk and it's no surprise that the disease was first recorded in India. Even in subtropical Brisbane I have negatives from the mid 1960s that are at an advanced stage and others from the early 1970s that are showing early signs. Storage conditions early in the life of a negative or transparency play an important role. Even if they are later transferred to archival conditions they are still likely to suffer degradation. I would encourage people responsible for collections of images on film in all climates to begin testing their collections with acid detecting strips which can usually be obtained from archival materials suppliers. So under what conditions should we be storing our film images? Ideally, if our film hasn't yet contracted the disease, 10 to 20° C with a relative humidity of 30 to 40%. If it is showing signs of vinegar syndrome it should be frozen at -25°C and 35%RH. If we are a large private or state run archival facility with computer controlled temperature and humidity we can store our film images under these ideal conditions. But what can the rest of us do? If we can find a way of controlling both humidity and heat we can extend the life of our film images. Every degree cooler and dryer helps, although it's not wise to lower the humidity below about 25%. There are humidity control devices on the market that work quite well and I've used one for many years, they are like small free standing air conditioners that remove the water from the air and collect it in a container. If the humidity is naturally low where you live you may only need to control the temperature. An important point here is that constancy is critical. A constant 20° C and 40% RH is better that one that fluctuates widely. Some facilities use domestic freezers to store film that has vinegar syndrome and they work well but need some kind of humidity control included with the film. It's also important that we use the right type of enclosure to store negatives and transparencies. Polyethylene, polypropylene and polyester sleeves are the only ones we should be using. Glassine or PVC should never be used. Does all film suffer from vinegar syndrome? Most of the film produced since the early to mid 1940s is known as "acetate" film but is actually a number of cellulose esters including cellulose di-acetate and the most common and recent one cellulose tri-acetate. These are usually labelled "safety film" and all of them suffer from vinegar syndrome. Some may smell slightly different to vinegar but any acrid smell is an indication of vinegar syndrome. The film that does not suffer from vinegar syndrome is polyester. We know it best as Kodaks' "Estar" film but a number of manufacturers used polyester in some of their products. Most APS format film is also a type of polyester. Polyester film is considered "archival" at this stage but it should not be stored together with acetate film suffering from vinegar syndrome as it's not known how the decomposition by-products of the acetate will affect it. There are a few other special purpose films that do not suffer from vinegar syndrome but were not used in general photography. The best way of identifying polyester film is through cross-polarised filters over transmitted light which will show red and green interference patterns indicating it is made of polyester. If you have negatives from before 1945 it's possible that they are on cellulose nitrate film. They should be stored separately from other film. Nitrate film is flammable and produces oxygen as it burns making it extremely difficult to extinguish. Extreme care should be taken with the storage of nitrate film as it's been known to ignite spontaneously if stored in significant quantities . It also degrades in a similar way to acetate film, releasing nitric acid. These symptoms are similar to vinegar syndrome but the smell is slightly different, being sweeter. Nitrate film should be placed into cold storage or frozen after being re-formatted. Re-formatting If we decide to freeze film but still require access to the images or if we find it impossible for whatever reason to provide temperature and humidity control, we will need to make copies of the images before they disappear into the freezer or oblivion. We call this re-formatting and can involve copying the image on to polyester film or making a digital copy of it. This is something that requires thought and planning and involves many technical issues, the most important of which is to ensure all of the information in the image is captured. It's likely that the copy will become the only one available and should be of the highest quality. Copying black and white images onto polyester film is by far the most "archival" method but is quite expensive if there are large quantities involved. Careful control of the exposure and processing is needed to ensure a faithful reproduction of all of the tones. Sharpness is best retained by contact printing but this is usually not possible for negatives that have buckled, another reason why early intervention is desirable. Processing of the film should be to the highest archival standards. Colour negatives and transparencies are a problem in that there are no polyester films available. Colour images are not considered "archival" mainly because of dye instability (The Cibachrome process being the exception) but usually last longer before the onset of vinegar syndrome than do black and white ones. It appears that the thicker gelatine emulsion plays a part in this. Colour images can be copied on to new acetate film which should be stored at 10°C and 35% RH. Again, contact printing is the best way to get high quality results. Those institutions holding colour images of high importance should consider re-formatting them on to polyester film using the tri-colour separation method. This involves separating the red, blue and green information using filters and copying each on to polyester black and white film. These negatives offer archival permanence and can be re-combined into a colour image using digital technology. Because of the high cost of re-formatting on to film many institutions choose to make digital copies which are cheaper but present a new range of issues for archival permanence. Digital storage is not considered to be "archival" but if carefully managed it can approach archival needs. Many institutions are introducing digital storage and management regimes. Issues such as media redundancy will need to be managed over long periods of time if it's going to offer us a real alternative to film. Large institutions have the means to do this but what can the rest of us do to preserve our digital images? Digital storage We know how important it is to back up digital files. For most of us that means burning them to CD or DVD, but discs are certainly not "archival". They have a life expectancy much less than our film images and some archivists are recommending a maximum safe life of only two years. No doubt this will vary depending on the quality of the discs we use but they clearly nowhere near match film for long term storage unless we can copy our images onto new discs regularly. We should only use the best quality discs and store each one separately in its own case. They should be stored vertically in the same temperature and humidity as for film (but do not freeze). Hard drives offer little more security but I like to keep three copies of my images, one on the inbuilt hard drive, one on an external hard drive and one on a DVD. Ideally, another copy should be stored either on DVD or hard drive with a friend or relative. I store them as RAW or TIFF files, not jpegs. For larger institutions I recommend they future-proof the images as much as possible. By that I mean they leave as many possibilities for future advances in technology as possible. Digital re-formatting should involve the highest optical scan with no interpolation, sharpening or editing and should be saved as a TIFF file. A sized, sharpened and edited Jpeg copy can be made for access purposes. Clearly, the long term storage of our images presents many problems and expenses and the inevitable fact is that it's not usually practicable to save them all. Considering the huge number of photographs that have been taken since the introduction of flexible film we have to make choices about which ones we'll save for the future. The criteria we use to make that selection will depend upon many subjective decisions. There are large image libraries and archives looking after our most important images and we can be thankful for that but they're only part of the story. The story of our time has a rich visual component that is held in small collections by individuals and institutions and whether they're on film or digital files they deserve to be preserved for as long as possible. I've worked with historically important images for many years and it's very difficult to predict whether an image will become important in the future. Present generations have had immense impact on the world and future generations will need to understand that story. Our photographs, however humble, may help with that understanding. If you have a collection of images on film that needs assessment I offer a consultancy service which includes:
Contact me at BrcCow@aol.com or bruce@brucecowellphotographer.com.au or by phone at: +617 32612246 (international) 07 32612246 (Australia) Mobile 0419 736 541
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Bubbling
Channelling
Emulsion side 
Channelling of the emulsion
Brittleness
