Museums are in a race against time to keep plastic art from falling apart | Science

Polyurethane foam “Nature Carpet” by Italian artist Piero Gilardi

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Along Sam Keen

Leanne Tonkin still remembers the ruined coat. When she saw the red Macintosh from the 1960s, she was a fellowship at the Costume Institute at the Metropolitan Museum of Art in the mid-2010s. The raincoat was so hard that I was able to stand on my own as if a ghost lived there. Another Macintosh was barely recognizable as clothing. “I was able to make a button, but it was completely melted,” she says.

Nothing unusual happened to the court. They were not involved in a fire or exposed to corrosive chemicals. Instead, they were destined for simpler reasons: they contained inherently unstable plastics.

People often complain that plastic is too durable. Plastics are everywhere and don’t break easily, so water bottles, shopping bags, and other debris are scattered all over the globe, from Mount Everest to the Mariana Trench.

However, some plastic materials change over time. They crack and curl. They “clean up” the additives. They dissolve in sludge. All of these are major headaches for institutions such as museums seeking to preserve culturally important objects.

Until recently, museums only had to worry about traditional materials. “We know how to work on the restoration of paintings, books, and materials such as wood, metal, and glass,” says Anna Lagana, a research specialist at the Getty Conservation Institute. “But our knowledge of plastics is still limited,” said Tonkin, who currently holds a PhD in fashion protection from Nottingham Trent University. “We now know how to protect plastics. I’m looking for it. “

Various endangered plastic objects such as early radio, avant-garde sculptures, still images of Disney movie celluloid animations, David Bowie’s costumes, and the first artificial heart are dazzling. Almost every museum in the world has plastic items, and even well-maintained objects can collapse surprisingly quickly.

After years of exposure, the foam shape of these “nature carpets” had cracked and deteriorated.

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Joanaria Ferreira, an assistant professor of conservation and restoration at the NOVA School of Science and Technology, recalls an exhibition with a lamp with a black polyurethane foam shade. One day, I noticed that the shade had begun to collapse, so I removed the lamp from the exhibition and saved it. But it was too late. The shade began to crumble and soon collapsed completely. “From one week to another,” Ferreira says. “It was on the floor.”

The museum is doing everything it can to save culturally important items from a similar fate. Over the last decade, parents have developed better tools for identifying vulnerable objects. Some restorers have also begun experiments to enhance conservation and restoration practices and prevent corruption. Plastic has existed for about 150 years at this point, and curators want to be able to recognize the treasures of plastic 150 years later.

Some plastic, Polycarbonate and acrylic are very stable. However, long-chain polymer molecules in other plastics, among other potential threats, can decompose when exposed to oxygen and light. Unfortunately, some of the most “malignant” plastics (cellulose nitrate, cellulose acetate, polyurethane, polyvinyl chloride (PVC)) have historically been common and range from photographic film, billiard balls, luxury clothing and furniture. It is used for various items. Additional ingredients in these plastics, such as plasticizers, dyes and flame retardants, can cause unique problems. For example, PVC forms both sturdy plumbing pipes and supple shower curtains, depending on the additives. And these mixtures can spontaneously dissolve over time, especially when the temperature fluctuates.

One of the common challenges for conservator-restorers is figuring out which material they are using. Techniques such as Raman spectroscopy and pyrolysis-gas chromatography-mass spectrometry can create “fingerprints” of molecules from sample materials.By looking for a match in Spectrum database The museum, posted online by a European-led project called POPART (Preservation of Plastic Crafts in the Museum’s Collection), can determine what materials it has.

Some polymers will fall apart

Different plastics decompose at different rates depending on their composition and environment. Some plastics, including those in the early decades of the 19th and 20th centuries, are fairly unstable (orange) and are common in culturally important plastic objects. Modern plastic (blue) is much more stable and can take centuries or more to disassemble.

Cellulose nitrate This plastic was used in early movies and consumers Goods can be flammable and dangerous.Polyethylene terephthalate (PET)PET, one of the most common plastics in the world Used for water bottles and clamshell food packaging.Polymethylmethacrylate)This often transparent polymer, also known as acrylic Common on LCD and smartphone screens.Cellulose acetate This polymer is an early Lego, engraving, and Fashion items such as belts. When it rots, it may smell like vinegar.PolyurethanePolyurethane, which is often used for foams, has the following molecular struts:After 10 to 20 years, it may deteriorate due to exposure.

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Still, many small museums lack access to luxurious laboratory equipment that can cost tens of thousands of dollars.Therefore, some institutions have developed a low-tech approach based on Touch, tap, sniffing.. Depending on the type, the plastic may feel like glass or waxy. You may also feel sticky as the plasticizer inside moves to the surface after the collapse has begun. Hearing tests are also available. Some plastics make a small noise when tapped. Others, hard and dull. Deterioration of plastic can also produce a surprising amount of odors such as chlorine, vinegar, pine, burnt hair, used sneakers, mothball, car tires, and sulfur.

Once the keeper has identified the plastic, you can take steps to preserve it. As a general rule, “Keep it cold, dark and dry, [and] In some cases, try to keep it oxygen-free, “says Getty Senior Scientist Odile Madden. However, optimal conditions can vary within the same family of materials. It all depends on the particular ingredients and their proportions. Testing new preservation techniques on unique objects is dangerous, so some preservers are looking to controlled experiments.

For example, Tonkin Simulated clothing By adding stitches and metal studs to a 20 cm square PVC fabric (common in modern raincoats). She then stored them at temperatures in the range –17.8 ° C to 21.1 ° C and humidity of 40% to 50% for several months.

Intuitively, quick freezing may seem like the most promising way to store materials. However, in the coldest conditions, Tonkin found that PVC molecules crystallized and squeezed out a plasticizer that made the dough supple. The dough has become brittle and has small holes. By storing the plastic at 4.4 ° C, we were able to avoid that problem. In addition, Tonkin found that when materials were taken in and out of refrigerated storage, they could be kept at an intermediate temperature of about 15.5 ° C for 24 hours to avoid damage from sudden temperature changes.

Other parents have experimented with artificially aging plastics, trying to understand exactly how plastics break down, and gathering clues on how to prevent spoilage. Xenon arc lamps irradiate materials with photons, causing years of exposure to collapse in hours. Researchers can use meteorological chambers to study heat and humidity. Madden also considered exposing plastics to pollutants to study the effects of polluted air.

Such experiments face limiting factors. The lack of historically accurate plastic. For safety and stability, today’s manufacturers are adding different ingredients to plastics than they have in the last few decades. Therefore, the results of experiments on modern polymers may not apply to historical ones.

Some of the nature carpets have been returned to the exhibition by the protective “sunscreen” treatment.

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To circumvent that limitation, Getty purchased its own plastic manufacturing equipment, an extruder and an injection molding system, in 2019. After that, the staff turned over the old issues of the following magazines. Modern plastic To find a representative recipe. Getty is now able to recreate historic plastics using the exact materials originally used. Scientists have already run stress tests on small discs and bars, and later aim to run artificial aging tests on them.

Certain artifacts are particularly vulnerable, as some pioneers of plastic arts did not always know how to mix the ingredients properly, says polymer chemist Thea van Austin. (RCE). “It’s like baking a cake. Without the exact amount, it won’t work,” she says. “The object you make is already a time bomb.”

And sometimes it’s not the artist’s fault. Italian artist in the 1960s Piero Girardi I started making hundreds of bright and colorful foam pieces. These pieces included a small bed of roses and other items, as well as dozens of “nature carpets” that were large rectangles adorned with foam pumpkins, cabbage, and watermelons. He wanted the viewer to walk around on the carpet. In other words, it had to be durable.

Unfortunately, the polyurethane foam he used is inherently unstable. Especially vulnerable to light damage, by the mid-1990s Girardi’s pumpkins, roses and other figures had split and crumbled. The museum trapped some of them in the dark.

So RCE van Oosten and his colleagues started studying. How to protect polyurethane.. First, they took a sample of foam that resembled a natural carpet and injected some of the stabilizing and fortifying chemicals commonly used by modern manufacturers. Van Oosten calls these chemicals “sunscreens.” This is because their goal was to prevent further light damage and reconstruct worn polymer fibers. The team then used a xenon lamp to artificially age both treated and untreated samples and inspect them under a high-magnification microscope.

The result was encouraging. Samples lacking sunscreen died under a barrage of photons. The molecular “struts” that support the foam were 42% thinner and more brittle than they were before the lamp treatment. Sunscreen sample stanchions were reduced by only 12.5%.

Armed with that knowledge, parents working with RCE have stabilized them by injecting sunscreen into several Girardi sculptures, including two natural carpets. Van Oosten, sometimes under a protective case, is proud to have some re-exhibited. for a long time”Plastic queenIn 2012, van Oosten became a knight in the Netherlands in an effort to preserve plastic objects and disseminate knowledge to other institutions.

Despite such success Talk, plastic storage will probably be difficult. Old objects continue to deteriorate. To make matters worse, biodegradable plastics designed to decompose are becoming more and more common.

And here more is at stake than individual objects. Ferreira states that archaeologists first defined the great material ages of human history (Stone Age, Iron Age, etc.) after examining museum relics. We are now living in the age of plastics. “And what we decide to collect today, what we decide to save … will have a huge impact on our perspective in the future,” she says.

Future archaeologists examining the remains of the 21st century may find swarms of toxic clads, along with lots of plastic debris. But if the museum’s conservation efforts are successful, perhaps those scholars will realize that today’s plastic products are culturally meaningful and can even be valued.

The museum is in the fight against time to prevent the collapse of plastic arts | Science

Source link The museum is in the fight against time to prevent the collapse of plastic arts | Science

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