Wednesday, March 23, 2016

Are Acrylics and Other Plastics Decaying?

Assessing damage and losses to an Andy Warhol painting
Acrylics and other plastics are disintegrating, and that's causing a problem for museum conservators.

Everything from space suits to crash test dummies to acrylic paintings by Andy Warhol are showing signs of degradation after as few as two or three decades.

Yvonne Shashoua with a 1970s-era crash-test dummy
that is leaking plasticizer
"Plastic objects are among the most vulnerable found in museums and galleries,” says Matija Strlič, a chemist at the Centre for Sustainable Heritage at University College London.

Depending on how the plastic was formulated, it might discolor, bleach, form a scaly crust, give off foul-smelling gases, leach out acid or sticky liquids, turn to goo, or become brittle and cracked.

According to the April, 2016 issue of Scientific American magazine, exposure to oxygen or ultraviolet light removes the electrons that bind the larger molecules of plastics together.

Lisa Young restores Neil Armstrong's spacesuit (source)
Astronauts' space suits are composed of a variety of materials, including unstable plastics. A New York Times article quoted conservator Mary T. Baker as saying: ''None of these suits will ultimately survive,.' ''In 500 years, there will be the Mona Lisa. But there will not be an Apollo spacesuit.''

Many plastics are composed of a complex mixture of dyes, stabilizers, surfactants, plasticizers, and antioxidants. Those ingredients can affect how the material behaves over time and what should be done to try to stabilize it. Unfortunately, the actual composition of many plastics are not known because the manufacturers kept them secret.

The plastics most prone to degradation are:
• PVC (polyvinyl chloride). PVC was used in crash test dummies, which are now weeping fake blood into display cases.
• Polyurethane, an ingredient in panty hose and sponges.
• Polyethylene (HDPE or high-density polyethylene). People who have stored water in old milk jugs may have noticed that they will spontaneously rupture.
• Cellulose nitrate and cellulose acetate. Cellulose was one of the first synthetic polymers, and was used extensively in making motion picture and photography stock. Cellulose is flammable, and it degrades "malignantly," meaning it releases nitric acid and toxic vapors as it breaks down, and the acid can corrode adjacent materials. Conservators have become adept at recognizing chemical changes through telltale smells.
• Acrylic polymers, used by artists such as Andy Warhol, David Hockney, and Mark Rothko since the paints were introduced in the 1940s as a more permanent alternative to oil paints.

Andromeda, 1962, acrylic, by Andrew Liberman
suffers from a whitish bloom
Using water to clean an acrylic painting can be risky as it can make the paint swell and lead to surface losses, according to a conservation scientist for the Tate museum.

[Edit March 24: Please see the comments after this post, where Mark Golden of Golden Acrylics argues that modern acrylics do not suffer any longevity or stability issues.]
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Read more:
"Choosing the Acrylic Paint that's Best for You" by Lindsey Bourret.
Scientific American, April 2016 "The Art of Saving Relics" (article is in the print edition)
New York Times "Mighty Moon Suits are Falling Apart"
Chemical and Engineering News: "Preserving Plastic Art"
Online: "Plastics Denial Syndrome"
Online: "When Acrylic Paints Get a Spa Day"

44 comments:

Eugene Arenhaus said...

This may involve not only acrylic paintings, but also oil paintings on acrylic grounds.

The question is, are modern acrylic binders more durable than those old ones which Warhol had used?

Also, does varnish help to protect the paint from decay?

Dena said...

I paint in acrylics so I'd love to know the answers too!

Susan Krzywicki said...

Irony after irony. Slightly sideways look: does this mean that all the plastic pellets and junk floating around in the ocean are also subject to this decay? We've been told that plastic bags will degrade our oceans for unconscionable amounts of time...I'm not sure I understand the difference.

elgin said...

I am sorry if what I say offends anyone's sensibilities, but this is a surprise to who? Plastics, all plastics, are, have been, and will be very vulnerable to the natural world, especially sunlight and radical temperature shifts. Yes they will decay in the ocean and have been, we just are putting it out there faster than it decays. If you doubt, put a variety of plastic items outside somewhere and come back every year for 20 or 30 years. Then extrapolate what you have seen for 200 to 300 years. Prove it for yourself. Acrylics were really created for house painting and adapted for artistic use when people were more interested in selling to the quick dry crowd. This will only get worse, so use what you want. This too shall pass.

Tom Hart said...

That's a real eye-opener of a post! It's comforting that in general oil paintings have stood the test of centuries. That's not to imply that they're immune to the effects of time, poor maintenance or chemical factors. Eugene's question about acrylic grounds is a very good one.

Lou said...

I can imagine this having a huge impact on museums. I doubt many conservators a couple decades ago planned that much if any of their future conservation budget would have to go toward preserving plastics.
Saddens me to think that money will be taken from preserving antiquities that have survived thousands of years to spend on objects that like much of our modern society are very transient in nature.

Bich Nguyen said...

Oh wow! This is very informative! I was taught in college that acrylic paints are more durable than oils. Guess not!

Lester Yocum said...

Which is more permanent, assuming each and their grounds are well prepared: Oils or gouache? Permanent in this case would refer to lightfastness as well as molecular stability. We recognize that certain colors within each media, like phthalos, are more fugitive than others.

Sunila Sen Gupta said...

@Susan Krzywicki the big difference is that in our oceans, 400 years of degrading plastics can mean many species of animals gone for ever and endless suffering for the creatures who swallow the pellets or get trapped in plastic bags. It may even be worse than though if these plastics start to leak poisonous chemicals who knows. So yes, less plastics please!

I do my best not to wash acrylics from my palettes down the sink, I sieve them and put them in the bin (if I had more I would probably recycle them)

Chris James said...
This comment has been removed by the author.
Chris James said...

Whew! Saves me the money and effort of buying a new suite of acrylics, as I was soon about to do. I'll stick with the few tubes I have and look to other means of analog painting. I wanted something that would work well for fairly large paintings but didn't require the drying time of oil.

Mark Golden said...

Dear James, It is truly disappointing to have to address these issues again that seem to creep into press every decade. It makes for great press, yet if one actually reads into the article and the resources, you would see that it is easy to conflate the dangers of some plastics in museums with all plastics in museums. The articles are right to point out the problems of expanded polyurethane foams, PVA's with migrating plasticizers, Nitrocellulose plastics, etc. But to suggest because conservators are just now sharing better methods for cleaning acrylic paintings with the idea that these materials are going to easily degrade is such an inappropriate leap. In fact, a good deal of evidence would suggest that these materials now celebrating their 70 birthday are going to stand up well to the test of time. The symposium, "Modern Paints Uncovered" at the Tate brought together conservation scientists and conservators from around the world to discuss the issues around these new materials and how to go about cleaning and conserving these mediums. Conservators trained in traditional techniques of cleaning and repairing oil paintings needed different tools to be able to work on acrylics. This work was incredibly elucidating in sharing these paths for appropriate treatments for acrylic paintings. But nowhere in this work was their any suggestion that the acrylics were not holding up well. We have documented a good deal of this work that is typically only available from conservation journals in our Justpaint.org for anyone that might be truly interested.

The debate around what mediums an artist to use should be around the aesthetics and ones own sensibilities, not on a false premise that these materials are going to fail the test of time. Thanks and please know I would be glad to address these issues in more detail but I've already gone on too long. Best, Mark Golden

Martha said...

Thank you! Fascinating and not entirely surprising. Vintage doll collectors have discovered the same thing with hard plastic dolls of the 1940s and 1950s. The smell they develop is unpleasant, and is the most serious symptom of deterioration, but there is also an oily residue, like the crash dummy.

James Gurney said...

Mark, thanks for your thoughtful response. Is your last name associated with Golden Acrylics? Regarding the post, I tried not to go beyond what was mentioned in the Scientific American article and the other articles in Chemical and Engineering News, both reputable scientific and technical journals that were quoting experts in the field. I didn't even go into the allegation of "plastics denial syndrome," which suggests that many conservators haven't really faced the problem. However, you have a point, and perhaps it would have been more accurate if I qualified the opening line to say "Some acrylics are disintegrating..." or some are disintegrating faster than others..."

I wonder if you could address specifically the questions that Eugene and others have raised:
1. Do the degradations mentioned in the article refer just to pure acrylic paintings, or also to oil paintings on acrylic grounds?
2. Are modern acrylic polymers different or more durable than those older ones which Warhol had used? If so, how are they different?
3. Does varnish help to protect the paint from decay?
4. Can you offer links to other scientific journals that make the case for the longevity of modern acrylics?

Rich said...

Hope Maurice Quentin's pastels will hold on for some time;-)

Very interesting post! Perhaps some innovative concepts at acrylic preservation for future conservators to come...

Mark Golden said...

Thanks again James! Many moving pieces here, as I am the co-founder of Golden Artist Colors for full disclosure, we also manufacture for the last 4 years Williamsburg Oil Colors and now QoR watercolors. There now it's out!

First there is no evidence for the claim that acrylic grounds are failing. In another blog, and this is like 'wack-a-mole' they claimed these dispersion grounds were made with zinc. Not likely as it's a difficult material to formulate with and why go through the trouble as Titanium Dioxide will get coverage so much faster and then additives like calcium carbonate and clay whiting. Acrylic grounds are incredibly robust. Their was a suggestion that acrylic films are non-porous, and therefor would not allow for adhesion of oil paint films. In fact, the porosity of the acrylic film is of concern to conservators for its ability to imbibe dust. But so much of this has been actually shared in the research and our own publications. Again, I'd point you to our JustPaint.org archive which not only has the articles that may be of interest to the group but also an extensive listing within most of the articles of the bibliography from which this research is drawn from. I will also take some time tomorrow to list out the most important articles, but again many are not available online in the popular press, but a simple trip to the library or a subscription through a college will allow for your access.

Although many paintings require cleaning, I have not heard of any catastrophic failure of the Warhol's because of the acrylics used. So I'm not sure why this was raised as an example in the authors research, other than to show a painting with loss and cleaning issues. But I'm sure you're aware that this is not the exclusive issue with acrylic. Varnish can help in many different ways and again these articles are available for your review in the newest compendium by edited Joyce Hill Stoner and Rebecca Rushfield, the Conservation of Easel Paintings. But even without varnish the acrylics are not in danger of self destruction! We've always recommending for artists that varnish is first an aesthetic choice and after that the varnishes can aid in assisting in the cleaning and conservation of works both in oil and acrylic. Varnishes or topcoats are probably most necessary for outdoor murals, that would be subjected to direct sunlight and UVB degradation. Dr. Paul Whitmore did extensive research on the failure of acrylic subjected to UVB degradation and under this sort of exposure, it can break the long chain bonds. But under UVA light, what one would get from direct sunlight through window glass, his research suggested that the acrylic is an incredibly durable material. Sorry, already too many characters in this reply! Best, Mark

Mark Golden said...

More...

Acrylics have improved and will continue to improve, as artists are working with them in thicker and thicker ways and requiring even greater clarity. Exciting opportunities for the future, but even the older acrylic, I would maintain, will still withstand the test of time, well into centuries and even millenium. The biggest changes in formulation occurred in the mid 90's with a conversion from Ethyl acrylate co-polymer with Methyl-methacrylate (MMA) to Butyl acrylate w/MMA

Some resources: Proceedings Modern Paints Uncovered; A Symposium Organized by the Getty Conservation INstitute, Tate, and the National Gallery of Art, Tate Modern, London, May 16-19, 2006. You'll find a wide range of articles and research on the topic of acrylic paints, their formulation and conservation. The articles in our literature will also point to significant contributions by Marion Mecklenburg who is probably the foremost authority on structural integrity of coatings. He provides a wonderful review of the embrittlement of oil paints vs acrylics as well as work on the adhesion of oils onto acrylic for his samples he's been collecting for decades. Hopefully work on his samples will continue to provide valuable data for years to come. Best, Mark

James Gurney said...

Thanks so much, Mark, for that detailed reply. Looks like everything came through on the comments.

K_tigress said...

In short. Everything has exploration date in this life even this universe, sadly. So I'm not surprised.

Pearl Shifer said...

I've had papers in plastic shopping bags that were left behind for 15 years, when I got back to them, the plastic bags were disintegrating.

Roger Bansemer said...

That's interesting because I did approximately large 1000 abstract paintings in the early 1970's and I still have maybe a hundred of them and they are perfectly fine with no cracking or discoloration. Many of the large paintings have been folded over in the middle and still no cracking.

Katherine Tyrrell said...

You can download a pdf copy of the 333 pages of Modern Paints Uncovered (Proceedings Modern Paints Uncovered; A Symposium Organized by the Getty Conservation INstitute, Tate, and the National Gallery of Art, Tate Modern, London, May 16-19, 2006) from the Google Books website.

Just go to Google Books - put in "Modern paints uncovered" in the search query box and then when it pops up use the menu under the "cogwheel" icon to download as a pdf

Garrett said...

Wow, tons of helpful info... There were always suggestions in art school that people like Warhol threw caution into the wind in terms of longevity, mixing all sorts of untested materials together... Perhaps it isn't necessarily the acrylic, but the way it was used or adulterated, or even displayed? Remember oil paintings left in sunlight do not fare well either.

There were also insinuations in art school that alkyds were evil and would turn your paintings orange/yellow... I also heard this was only a problem with the old varieties of liquin.. This is something that seriously worries me because I'm thoroughly addicted to the stuff... My oldest painting is not yet 15 years old, but so far they haven't changed color. If anyone has info on alkyds, I'd love to hear it!

MoStarkey said...

I've been painting with Acrylics for over 40 years. Other than those images that were constantly exposed to extreme sunlight or were water damaged, they've remain just fine. This is a sobering article. I'm so glad Mark Golden spoke up. Golden reliable acrylics and it's great to have a ceo show such confidence in his product. I would like to see how companies,(all of them, not just Golden) test their paint. Thank you for another great entry.

JoAnn Sanborn said...

I have been using acrylic paints since the seventies and the ones I still have in my possession show no deterioration of surface or color. Oil paints often craze, flake and fade over time. This article is most likely talking about a few ill-constructed pieces. Thank you, Mark Golden, for your knowledgeable comments.

Karen Bowden said...

I, too, have several paintings I did in the 70's in high school. To my eye they still look as they did then. And they have no smell. I'll admit that a couple of them have been stored in a box so not exposed to a lot of light. However, I have another almost as old that has been propped up on a bookshelf and it's doing just fine. And on top of all that, these were paintings I did as a student so were done on canvas boards.

indigo wendigo said...

Wow. I have recently moved to using only golden open acrylics. The irony of this news is that it doesn't bother me. Open acrylics have revolutionized my approach to painting to the point that I probably would still use them even if there was a long term issue. As Rockwell said, "Let the next generation paint it's own pictures." But I believe Mr. Golden and I'm not worried. Open acrylics are designed to be used by human beings! As a person who can't blend a subtle flesh tone in ten minutes, I don't like regular acrylics. I've used oil for twenty years, always frustrated by the tedious drying times. I'm a bit ADHD, and I must strike while the iron is hot! Opens allow me to work a section, go for lunch, and begin glazing when I return, not 3 days later. Every person who sees my work from this year insists it must be oil. And while I'm up here on my soapbox, Ampersand pretoned Pastelbord is an exquisite surface to use these paints on. So, thank you Mr. Golden. I compare this material advantage to the leap from egg tempera to oil paint.

Tom Hart said...

This discussion has been informative on many levels. Personally, I currently gravitate toward oil. The reasons for that are varied and, come to think of it, the medium's relative longevity is only one of many factors. As an old art teacher once told me (in reference to critiques): consider the source, weigh the input against all other considerations, and then get to work. One of the things I love most about art is that - like life - it's a matter of finding the balance that works for you.

Gavin said...

In reply to a couple of the comments. I have experienced problems with liquin when used just over a decade ago - it's yellowed very badly in my experience. These days I just use turpentine and a little linseed oil if I need any medium at all.
I've also used alkyds (W&N) several times, again over a decade ago now, and I've seen no discernible signs of yellowing, cracking or aging so far.

Joel Fletcher said...

I still have acrylic paintings in my possession that I created in the 70's, that have zero discernible change to their appearance. It may be anecdotal, but I figure 40 years with no problem means acrylic paints are durable and excellent materials. And possibly superior to oils for longevity and color stability, but that will not be known for certain in our lifetimes.

I agree with Mark Golden that this article implies that there are deterioration problems with acrylic paints, which is unjustified. If you read the articles cited, they state that SOME plastics are unstable. The only statement about acrylic paints is the issue with the Warhol piece… but who knows if he used cheap paint, or practiced unsound methods in its construction? Plastics vary widely in their chemical makeup, and definitely are not the same.

Cpaul said...

Just let them dry on the palette, spritz them with water and scrape with a little window cleaning razor blade. All of it goes to the garbage that way

Brad Teare said...

Acrylics have changed a lot over the decades. I know Jackson Pollock used latex house paints and in those days they were very different from the acrylics we use today. His paintings aren't faring very well. So maybe Warhol used a mixture of commercial house paints. I switched from oils to acrylics (with my large abstracts) when some of the paint films on my extremely thick oil paintings failed. I haven't had that problem with acrylics. In general I think it's better that consumer plastics decompose. I'm reasonably confident that acrylics such as Golden Acrylics maintain their structure over decades if not centuries. As always, I enjoy your insight. Thanks for the great post!

Roberto said...

Great Post James, and Mark Golden’s input is much appreciated.
But I think everyone missed the most important concern that the article raises…
What’s with those Space-suites!!

I’m not flyin’ till this problem is satisfactorily addressed! ;p -RQ

Jamie Williams Grossman said...

Like others here have stated, I've done acrylic paintings that are over 40 years old and show no signs of change. I'm glad Mark Golden chimed in above; I hope everybody will read his comments. It's good to know that acrylic paint has gotten even better, in spite of the fact that my older paintings (for better or for worse!) are fine. I love oil, acrylic, gouache, watercolor, pastel, casein... Wouldn't want to be without any of it, and don't plan to surrender my acrylics anytime soon! Variety is always a good thing. I hope all art materials manufacturers continually move in the direction of better longevity and durability, as the Golden company has done.

Susan Kraft-Yorke said...

So glad to see your response, Mark. I knew you'd have great information to add.
Susan

Lars Grant-West said...

Great article, Jim. Informative and reassuring, especially for discussions with students, where this has come up.

Thank you!

Patricia Smithen said...

Both the the Warhol and the Liberman paintings at Tate pictured above are in excellent condition. The monitoring was to establish measurements so we could monitor our surface cleaning treatment and any future changes over time. Get to see the remarks from Mark Golden and the many of you who have been painting successfully with acrylics for so many years.

Tom Hart said...

Even though I paint primarily with oils, as mentioned above, I have acrylics (Golden, as it happens) in my "arsenal" so the positive comments about acrylics are reassuring. Patricia, am I correct in understanding that you are professionally associated with the Tate and/or the assessment of the Warhol and Liberman?

James Gurney said...

Patricia and Mark, What makes some polymers (such as polypropylene, Kevlar, and LDPE) so highly susceptible to UV degradation? (I remember making a swing on a tree in the backyard out of polypropylene rope, and the rope failed after less than a year in the sun.)
Presuming that modern artists' acrylic polymers are different in there UV sensitivity, what makes them less prone to damage from sunlight? Do modern acrylics use UV stabilizers to dissipate the energy by preferential absorption?

Patricia Smithen said...

Hi Tom. Yes I used to work at Tate and was the conservator cleaning these paintings for the Tate-AXA Art Modern Paint Project. Dr. Bronwyn Ormsby wrote up all the projects which include our treatments and you can see these on the Tate's website if you are interested.

Joel Fletcher said...

James, your question above about UV degradation raises valid concerns. I don't know the answer, but one thing is certain; sun rays are extremely powerful, and very few man-made material will last long when left outdoors in the sun and weather. As for paints, all will ultimately not fare well in full sun. But guess what? The paint in question, acrylic, is the paint of choice for durability and lightfastness in outdoor murals. Which says a lot. Enamel holds up pretty well outdoors too. Any other paint would fail far more rapidly in the elements compared to acrylics!

The thing is, most artistic creations are kept in fairly protected environments. We should only be concerned about their longevity under normal care and circumstances, not extremes such as exposure to excessive UV radiation, heat, and moisture. However, it is important to make informed, wise choices about the long-term life of our materials. Fortunately we have a lot of information available these days to aid us in those decisions.

Mark Golden said...

James, your question is exactly the right one. What makes one polymer, whether synthetic or not more subject to methods of environmental deterioration. In the case of many of these synthetic plastics, like PVC, Polypro, Styrene they can deteriorate quickly upon exposure to UVB (outdoor UV exposure). Their strength against the strong energy of the sun is based upon the weakest link in their bond strength. In the case of Polystyrene the break down of the plastic is from chain scission (breaking of bonds holding the polymer together). This is precipitated by the absorbing of UV energy into the benzine ring of the styrene, which then transfers this energy to other C-C bonds and to C-H bonds breaking those weakest bonds and forming reactive free radicals that in a chain reaction continue the process of chain scission and ultimately leading to the failure of the material.
The acrylic is a very different chemistry. Although as I shared earlier, acrylics can also be broken down by UVB (very powerful UV energy) and in a similar manner the acrylate polymer in the matrix also suffers chain scission at the weakest link (a tertiary hydrogen) which begins a process of free radical formation. Although it is suggested that the methylmethacrylate (another part of this polymer matrix) actually undergoes cross linking, or combining with other entities in the acrylic. Fortunately, the acrylic polymer is much more resistant to these changes caused by UV light than other polymers including both synthetic and natural polymers. So under indoor conditions, the acrylic continues to remain flexible and maintain strong bonds. Each synthetic polymer or natural polymer has a different mode and route of degradation. It is unfortunate to group all these materials together as if the public is not intelligent to understand that these materials have quite different uses, characteristics and permanency under various conditions. The article, especially in Scientific America could have and should have done a better job. For example epoxies have the greatest chemical resistance and work incredibly well under the extremes that would damage any other natural or synthetic polymer. Again, I know too long... best, Mark

James Gurney said...

Mark, I really appreciate the detailed explanation. A lot of my blog readers (and me too, since I use acrylics for part of my process) will be relieved to read your explanation of how good artists' acrylics are formulated to resist degradation. Thanks to your help, I think this back-and-forth dialog is one of the reasons that social media can be more responsive and informative than print media are able to be.

Mark Golden said...

James, thanks for the space and opportunity to create greater clarity on this subject. If one were to claim that all oils are the same, my colleagues, you and your audience would quickly provide data and resources to share that in fact they are not. Nor would it surprise anyone if we shared that even the best oils have problems and will harden and become brittle and yellow over time. This does not make them less important, but we've learned over 600 years of practice and trial and error how to mitigate these problems: To use better varnishes, to work with more rigid supports, to keep our work out of direct sunlight, to work with appropriate understanding of technique. All of these in an effort to produce work that will remain beautiful and intact for centuries.
Similarly, not all plastics are the same and more importantly for this discussion, and the piece that got buried in the article, is that acrylics, even the best ones, also have problems we have to confront as well. They are soft, they can mar and imbibe dirt, and traditional techniques developed to over centuries cannot successfully be used in modern conservation of acrylic paintings. So again we need an understanding of the material to help mitigate these issues. Varnishing when possible, isolation coats, protecting the work during shipping, avoiding shocking or hitting the work in cold temperatures. So the real research mentioned in the Scientific American articles is ongoing and very important. It came out of the very important symposium which we've listed previously, 'Modern Paints Uncovered'. Here's a quote from one the lead scientist at the Tate, Dr. Bronwyn Ormsby, "With an ethical and innovative approach, there is hope that modern acrylic art will last as long as the Sistine Chapel frescoes." It was quite unfortunate that every problem with the entire range of plastics and its longevity, was conflated with important issues being researched in the acrylic cleaning studies. But it sure makes a much better headline "Are Acrylics and other plastics failing". The real failing was in the magazine. Thanks again, Mark