Vinegar Syndrome: A warning for cel collectors
Posted: Sun Jan 06, 2013 8:35 pm
I’d like to give wider notice to a problem that could potentially affect many cel collectors, especially those who are interested in pre-1990s anime. The issue is that the medium used for the manufacture of cels is chemically unstable, and has the tendency to break down over time. The chemical name for the plastic used for cels is cellulose acetate. This material replaced the older matrix for flexible film stock, which was cellulose dinitrate. This, in turn, replaced celluloid proper, which was too stiff and too unstable to use for most purposes. All are produced by treating the natural plant product cellulose with some kind of acid, changing its chemical structure and allowing it to be melted and then turned into transparent sheets for use in photographic film, microfilm/microfiche, or, as we have come to know, animation “cels.”
All of these materials, a variety of online sources confirm, have the odd property of remaining stable for long periods of time, then rapidly deteriorating in a way that not only destroys the images printed or painted on them, but also the materials stored in their vicinity. This is because the most serious aspect of the reaction is the release of the acid used to treat the cellulose. That’s nitric acid in the case of nitrate film/cels, and acetic acid (aka “vinegar”) in the case of acetate-based film/cels. Once the reaction begins, the free acid causes the molecules it contacts to break down, releasing more acid. This can take a long time to occur in a way that is detectable, as the reaction typically occurs inside the cel sheet, and only gradually travels to its surfaces. When this happens, the first symptom is a distinct chemical smell that resembles strong vinegar.
The process, once it starts, is irreversible. Worse, it is contagious, affecting cels that are stored with it or near it. The reaction can damage and penetrate cel bags and contaminate paper sheets, such as production backgrounds or the black “acid-free” sheets used in the pockets of Itoya portfolios.
I received two descriptions of “worst-case scenarios” recently. Neither collector wished to be identified, and so I’ve not given any information that would identify the cel or series. However, even though one came from a 1977 series and the other from a 1998 series, the events both persons described were essentially the same.
Collector 1 bought the cel from a respected seller on a Japanese auction site. When it arrived, the cel appeared to be in good condition, but the douga that had come in the same bag had a strong chemical smell. The collector let both air out thoroughly, then gave the cel a new bag and stored it normally in an Itoya cel book. The douga, which continued to have the smell, was stored in a different place.
Five years later the collector noticed that the chemical smell had come back in the room where the cels were stored. The culprit was the cel. As the collector described it, both the cel bag and cel were wrinkled, and the cel was stuck to its bag. On prying the two apart, the paint texture was no longer hard but soft and sticky. The plastic had visibly warped and distorted, and there was a visible “sweat” on the surface of the cel. When it was wiped off, the surface underneath turned from transparent to a translucent gray.
In addition, cels stored on nearby pages showed some minor warpage and also had the chemical smell, though to a lesser degree. The collector noted that these were not necessarily the ones stored adjacent to the deteriorating cel, though they were ones from the same series and studio, suggesting that the stock used at this time was, perhaps, cheaper and more prone to deterioration. After removing all of these, the chemical smell persisted until the collector also removed the black paper from the pages where the affected cels had been stored. It seems that this paper absorbs and traps the chemical smell, continuing to give it off even when the cel is no longer present.
Collector 2 purchased the affected cel in 2010 and did not notice any signs of trouble at this time. It was a four-layer set-up, all of them stuck together, along with the original production background. About two years later, this collector was doing a routine visual inspection of cel books and noticed an incredibly foul, vinegary odor. The scent was traced to its source, and the set-up was pulled for inspection. There was a clear liquid visible between the third and fourth layers of the stack of cels, and the bottom cel was not only soft to the touch but bent like damp paper. The collector separated the cels and tried to wipe off the liquid with some ordinary tap water. As a result, the soft part of the cel visibly warped and turned white or cloudy. The background, which had been stored next to the stack of cels, but in its own cel bag, also had picked up the same vinegar smell. The collector discarded the cel bags and carefully washed all the instruments that had come in contact with the affected cel to prevent contamination of other items in the collection.
Both collectors had used normal precautions in storing these cels and could point to no dramatic changes that could have precipitated the reactions. Since the beginning of the acute phase of this process, they have monitored the cels closely and find that they continue to smell of vinegar but have deteriorated less rapidly now that they are being stored in a setting where they can air out continually.
I’m collector 3, though my story is not as dramatic. I purchased two cels from a pre-90s series last year, and when I received them and removed them from their cel bags, I immediately noticed a heavy vinegary odor. The first was a four-layer cel set, stuck together, and I could see that the trouble lay at the place where the bottom two layers were most tightly stuck. The second, a less severe case, was a three-layer set, and again the problem came where the middle layer was stuck to the bottom. With a little paint damage, however, I was able to separate the layers, and I immediately quarantined both sets, sandwiching all the cels with MicroChamber paper and placing them in wide-open bags so they could vent the fumes. So far I have not yet seen any really catastrophic damage, but I’ve had to replace the MicroChamber paper for both, as the fumes have built up enough to surpass its neutralizing capabilities.
The most distinctive characteristic of my sets, other than the distinctive vinegar odor, is the prominent warping of the cel layers above the trouble spot, and a distinctive “washboard” rippling of the top of the cel around the central registration hole. So far I have not yet spotted the fluid discharge or clouding of the plastic noted by the other two. However, the cels have not and will not be housed with my others. And as a precaution I added a sheet of MicroChamber paper to all the other cels that I own from this series, even though I have not yet detected any odor as prominent as that given off by these two sets.
I’ve looked over a number of sites dealing with vinegar syndrome and the problems of various kinds of cellulose-based plastics, and also some sites dealing with the strategies being used by libraries to postpone or, if possible, avert this kind of deterioration. Here are a couple of preliminary conclusions.
1. All sources agree that cellulose acetate is intrinsically unstable and especially vulnerable to deterioration. An especially interesting web article for collectors of knives (whose handles are often made of celluloid materials) called the material “a time bomb which no doubt can and could destroy some special [items] that you have in your collection.” So vinegar syndrome and other signs of trouble will probably become part of most serious collectors’ experience as time goes on.
2. There are many unknown factors in this process, especially what environmental factors trigger the start of the acute process. But there is agreement that high heat, especially in humid conditions, will predispose celluloid objects to self-destruct. So a cel that has been stored in a non-air-conditioned storage facility in Japan may be a ticking time bomb from the moment you obtain it. However, a second predisposing factor is storing them in ways that allow fumes to build up inside the containers, allowing the reaction to fester and spread. (The reaction was first described in India, when movies on alleged “safety film” were found to be decomposing inside air-tight cans stored in outdoors sheds.) So housing cels inside plastic boxes or in sealed cel bags may also encourage their slide toward deterioration.
3. That said, the Disney Animation Research Library, which maintains a “state-of-the-art storage facility,” has observed that many of its vintage holdings now exhibit signs of celluloid deterioration, including yellowing, warping, and cracking of cel paint. So we probably should reconcile ourselves to the limited lifespan of any cel, however well maintained.
4. That said, there should be more attention given what Karen Hong Saracino calls “prudent general care” for cels. This includes
1. Handling cels infrequently and cleaning them in the least intrusive way possible
2. The use of MicroChamber paper or mats in the storage space
3. Storage in a low light or no-light environment, with relative humidity level of about 50 percent (lower can cause brittleness), and a temperature range of between 68-72 degrees F.
4. Physical examination of all cels should every three months to check for signs of trouble, and thorough airing-out of every one of them once a year.
All of these materials, a variety of online sources confirm, have the odd property of remaining stable for long periods of time, then rapidly deteriorating in a way that not only destroys the images printed or painted on them, but also the materials stored in their vicinity. This is because the most serious aspect of the reaction is the release of the acid used to treat the cellulose. That’s nitric acid in the case of nitrate film/cels, and acetic acid (aka “vinegar”) in the case of acetate-based film/cels. Once the reaction begins, the free acid causes the molecules it contacts to break down, releasing more acid. This can take a long time to occur in a way that is detectable, as the reaction typically occurs inside the cel sheet, and only gradually travels to its surfaces. When this happens, the first symptom is a distinct chemical smell that resembles strong vinegar.
The process, once it starts, is irreversible. Worse, it is contagious, affecting cels that are stored with it or near it. The reaction can damage and penetrate cel bags and contaminate paper sheets, such as production backgrounds or the black “acid-free” sheets used in the pockets of Itoya portfolios.
I received two descriptions of “worst-case scenarios” recently. Neither collector wished to be identified, and so I’ve not given any information that would identify the cel or series. However, even though one came from a 1977 series and the other from a 1998 series, the events both persons described were essentially the same.
Collector 1 bought the cel from a respected seller on a Japanese auction site. When it arrived, the cel appeared to be in good condition, but the douga that had come in the same bag had a strong chemical smell. The collector let both air out thoroughly, then gave the cel a new bag and stored it normally in an Itoya cel book. The douga, which continued to have the smell, was stored in a different place.
Five years later the collector noticed that the chemical smell had come back in the room where the cels were stored. The culprit was the cel. As the collector described it, both the cel bag and cel were wrinkled, and the cel was stuck to its bag. On prying the two apart, the paint texture was no longer hard but soft and sticky. The plastic had visibly warped and distorted, and there was a visible “sweat” on the surface of the cel. When it was wiped off, the surface underneath turned from transparent to a translucent gray.
In addition, cels stored on nearby pages showed some minor warpage and also had the chemical smell, though to a lesser degree. The collector noted that these were not necessarily the ones stored adjacent to the deteriorating cel, though they were ones from the same series and studio, suggesting that the stock used at this time was, perhaps, cheaper and more prone to deterioration. After removing all of these, the chemical smell persisted until the collector also removed the black paper from the pages where the affected cels had been stored. It seems that this paper absorbs and traps the chemical smell, continuing to give it off even when the cel is no longer present.
Collector 2 purchased the affected cel in 2010 and did not notice any signs of trouble at this time. It was a four-layer set-up, all of them stuck together, along with the original production background. About two years later, this collector was doing a routine visual inspection of cel books and noticed an incredibly foul, vinegary odor. The scent was traced to its source, and the set-up was pulled for inspection. There was a clear liquid visible between the third and fourth layers of the stack of cels, and the bottom cel was not only soft to the touch but bent like damp paper. The collector separated the cels and tried to wipe off the liquid with some ordinary tap water. As a result, the soft part of the cel visibly warped and turned white or cloudy. The background, which had been stored next to the stack of cels, but in its own cel bag, also had picked up the same vinegar smell. The collector discarded the cel bags and carefully washed all the instruments that had come in contact with the affected cel to prevent contamination of other items in the collection.
Both collectors had used normal precautions in storing these cels and could point to no dramatic changes that could have precipitated the reactions. Since the beginning of the acute phase of this process, they have monitored the cels closely and find that they continue to smell of vinegar but have deteriorated less rapidly now that they are being stored in a setting where they can air out continually.
I’m collector 3, though my story is not as dramatic. I purchased two cels from a pre-90s series last year, and when I received them and removed them from their cel bags, I immediately noticed a heavy vinegary odor. The first was a four-layer cel set, stuck together, and I could see that the trouble lay at the place where the bottom two layers were most tightly stuck. The second, a less severe case, was a three-layer set, and again the problem came where the middle layer was stuck to the bottom. With a little paint damage, however, I was able to separate the layers, and I immediately quarantined both sets, sandwiching all the cels with MicroChamber paper and placing them in wide-open bags so they could vent the fumes. So far I have not yet seen any really catastrophic damage, but I’ve had to replace the MicroChamber paper for both, as the fumes have built up enough to surpass its neutralizing capabilities.
The most distinctive characteristic of my sets, other than the distinctive vinegar odor, is the prominent warping of the cel layers above the trouble spot, and a distinctive “washboard” rippling of the top of the cel around the central registration hole. So far I have not yet spotted the fluid discharge or clouding of the plastic noted by the other two. However, the cels have not and will not be housed with my others. And as a precaution I added a sheet of MicroChamber paper to all the other cels that I own from this series, even though I have not yet detected any odor as prominent as that given off by these two sets.
I’ve looked over a number of sites dealing with vinegar syndrome and the problems of various kinds of cellulose-based plastics, and also some sites dealing with the strategies being used by libraries to postpone or, if possible, avert this kind of deterioration. Here are a couple of preliminary conclusions.
1. All sources agree that cellulose acetate is intrinsically unstable and especially vulnerable to deterioration. An especially interesting web article for collectors of knives (whose handles are often made of celluloid materials) called the material “a time bomb which no doubt can and could destroy some special [items] that you have in your collection.” So vinegar syndrome and other signs of trouble will probably become part of most serious collectors’ experience as time goes on.
2. There are many unknown factors in this process, especially what environmental factors trigger the start of the acute process. But there is agreement that high heat, especially in humid conditions, will predispose celluloid objects to self-destruct. So a cel that has been stored in a non-air-conditioned storage facility in Japan may be a ticking time bomb from the moment you obtain it. However, a second predisposing factor is storing them in ways that allow fumes to build up inside the containers, allowing the reaction to fester and spread. (The reaction was first described in India, when movies on alleged “safety film” were found to be decomposing inside air-tight cans stored in outdoors sheds.) So housing cels inside plastic boxes or in sealed cel bags may also encourage their slide toward deterioration.
3. That said, the Disney Animation Research Library, which maintains a “state-of-the-art storage facility,” has observed that many of its vintage holdings now exhibit signs of celluloid deterioration, including yellowing, warping, and cracking of cel paint. So we probably should reconcile ourselves to the limited lifespan of any cel, however well maintained.
4. That said, there should be more attention given what Karen Hong Saracino calls “prudent general care” for cels. This includes
1. Handling cels infrequently and cleaning them in the least intrusive way possible
2. The use of MicroChamber paper or mats in the storage space
3. Storage in a low light or no-light environment, with relative humidity level of about 50 percent (lower can cause brittleness), and a temperature range of between 68-72 degrees F.
4. Physical examination of all cels should every three months to check for signs of trouble, and thorough airing-out of every one of them once a year.