Cultural values ​​made of plastic begin to fall apart

Original author: XiaoZhi Lim
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Museum curators are in a hurry to figure out how to preserve contemporary works of art and historical objects falling apart.

Dr. Odile Madden of the Getty Conservation Institute in Los Angeles holds a piece of degrading plastic used in research on new storage methods

Neil Armstrong's suit keepers at the National Aerospace Museum knew this would happen. This engineering marvel is made of 21 layers of various types of plastic - nylon , neoprene , mylar , polyethylene terephthalate , kapton and teflon .

The neoprene rubber layer is the biggest problem. Although he is invisible and is under other layers, he, as assumed by the guardians, must harden and become brittle with age, because of which the suit must acquire the hardness of the board. In January 2006, the spacesuit was removed from the display case and placed in storage to stop degradation.

Of the estimated 8,300 million tons of plastic produced to date, about 60% float in the ocean or lie in heaps of garbage. Most people want this plastic to disappear. But in museums, where objects should be kept forever, plastic does not stand the test of time.

The suits in the National Aerospace Museum that Neil Armstrong and Buzz Aldrin wore on the moon.

“The heart is breaking,” said Malcolm Kollum, chief museum curator. The degradation of the Armstrong suit was delayed. But in other spacesuits belonging to a part of the history of astronautics, neoprene had already become so brittle that it broke up into pieces inside the layers, and their noise painfully reminds of the failure of the material.

Time does not spare art either, as Georgina Reiner, a scientist, a conservation expert at the Harvard Museum of Art, demonstrated at the meeting of the American chemical community in Boston in August 2018.

False Food Choices Clasa Oldenburg, a wooden box in which plastic food molds lie such as eggs and bacon, banana and oatmeal cookies, apparently rotting. Egg whites turn yellow, and the banana is completely blown away.

In museums, the problem is becoming more and more obvious. Reiner said in an interview: "The end of the life of plastic comes right now."

Of all the materials, plastic is worse than others. “Plastic really annoys me,” said Kollum. Because of the unpredictability of the material and the huge variety of types of degradation, he said, "the world of plastic is completely different."

“Compared to other materials, the history of this is too short for us to understand how long it can be stored,” said Hugh Shockie, lead curator at the St. Louis Art Museum.

Metal, stone, ceramics and paper have been living for several thousand years, and plastic is hardly more than 150 years old. But in such a short time it became dominant among the materials we used. Also, plastic has increasingly become found in works of art and artifacts selected for preservation.

This becomes clear after a walk through the various museums of the Smithsonian Institution. There is art: acrylic paintings, parabolic polyester lenses with a mirrored surface, a sculpture of a middle-aged woman preparing to eat a banana-shaped ice cream made of fiberglass.

There are triumphs of the human genius: the first artificial heart, the Ella Fitzgerald record, the Apple I computer, the D-Tag device, which helped researchers track and save the endangered southern whales .

There are also everyday objects describing human life: an electric can opener for canned goods, a Pink Princess dial-up telephone, plastic containers, 48 ​​lids for coffee glasses (all different in appearance).

“Such objects are in the collection of any museum, especially historical objects - they take you back to the past. But the material side of keeping this moment in time is very complicated, ”said Odile Madden, a plastic conservation specialist at the Getty Conservation Institute in Los Angeles.

On the left, the first fully artificial heart implanted into the human body in 1969. On the right is Dewain Hanson's Woman to Eat Sculpture from 1971, which used several types of plastic.

Dr. Madden pulls the cellulose acetate thread from the extruder

Dr. Madden is leading a small initiative group of contemporary art research scientists (Modern and Contemporary Art Research Initiative, abbreviated ModCon), working to help the plastics last for centuries.

The first step for custodians and other people will be to determine what plastic is.

“We use this word as one thing, although in reality hundreds and thousands of different things are plastic,” said Gregory Bailey, curator of the Smithsonian American Museum of Art.

Plastic is simply called something that can be molded. Often plastic is a mixture of polymers — large molecules that look like long chains — and additives made up of small molecules. The very first plastics were made from modified natural polymers like cellulose, but most modern plastics are based on synthetic polymers that last much longer.

Additives may be so-called. plasticizers that improve flexibility, or fillers that enhance the material.

“There are opacifiers, dyes and sometimes even shine,” Madden said. “The result is a huge number of possibilities for plastic composition.”

The Getty Institute stands on a hill, so on a clear day you can see the Pacific Ocean from it. One afternoon, Anna Lagena, the keeper, was digging into a bucket full of plastic objects, some of which were dull, some broken into pieces.

The objects belonged to the reference collection used in the study of advanced methods of plastic preservation. “This is the whole drama of the situation,” she said.

She pulled out a toothbrush that split in half. At the ends of the debris, the plastic handle remained transparent, although yellowed. Near the break, the brush was opaque, as if a cloud of white flowers had blossomed inside the handle.

Madden placed the broken brush under the microscope.

“Our area began with rudimentary physical checks, such as a dough with a hot needle,” which they put on the surface to see if the plastic melts, she said. “If there is a smell, does it look like coniferous?” Does it look like burnt hair? ”

Toothbrush from the institute's core collection

Today, conservation experts use advanced analytical technologies, such as microscopy and spectroscopy, to identify materials.

Under the microscope, white clouds on the handle of the brush turn into a tangled system of faults, from which other faults extend. Lagena and Madden instantly determined that this plastic was made from nitrocellulose , an old material that was often used in the production of photo and film.

The keepers have seen damage of this kind many times already. “No other plastic gives such breaks of such a shape,” said Lagena.

Scientific analysis is usually supported by archival research. “We spend a lot of time studying the history and production of these things,” Madden said. “If we find a Lego cube made before 1960, I would expect it to consist of cellulose acetate , not ABS.”

In the case of objects for which there is no information, a good option would be to start with spectroscopy, analyzing the interaction of molecules with light.

Madden carried a vase in white and green stripes, and a small red device. The latter shines through infrared light, explains Michael Dutra, a scientist at ModCon.

By absorbing infrared light, the bonds between different atoms inside the molecules will bend and stretch in a certain way, as distinctive as the movements of a particular dance. By studying these movements recorded on the graph, scientists can determine the type of bonds and try to make a conclusion about the molecules.

Lagena holds the vase still while Madden touches it with the tip of the spectrometer. “It seems to me that it is polyethylene or polypropylene,” says Lagena, and her guess is based on the tactile sensations from the vase and its smell.

Madden, on the right, with Melissa David, an intern, use infrared spectroscopy to penetrate materials and better understand their composition.

On the left, Michael Dutre is experimenting with squeezing cellulose acetate. On the right are plastic cubes used to replace lost fragments, broken corners and missing parts using a 3D printer.

Dutra launched an analysis procedure on a computer, and a graph appeared on the screen. Lagen was right - the graph shows only the simplest bonds between carbon atoms and between carbon and hydrogen.

“The absence of certain features suggests that it is polyethylene,” said Dutra.

Madden gets what was previously powder, but now her cap is very distorted, cracked and covered with a layer of white powder.

“Plastic has lost a certain percentage of mass,” she said, due to the fact that the plasticizer came to the surface and took on the appearance of white powder. Without a plasticizer, the box became fragile, shrank, and finally cracked along the sides. Drying and infiltration of additives are the two most common areas of plastic degradation.

The curators of the Smithsonian Institution Store found that a brown stain appeared on the left side of the Armstrong spacesuit’s torso — this plasticizer came out of PVC ducts .

This is due to the fact that molecules in plastics do not line up in the most efficient way, says Jane Lipson, a specialist in physical chemistry from Dartmouth College.

They are similar to frozen disorganized liquids, in which there are many gaps of random size between molecules. Over time, large polymer molecules are slowly organized and packaged more efficiently, which is perceived as compression with the naked eye.

Any additives consisting of small molecules percolate through the gaps until they reach the surface, turning into something like a sticky liquid or white powder. When warming up, plastic degrades faster, because molecules have more energy to move. “They are essentially finding a way to move to a more stable state,” Lipson said.

Keepers often try to find the best conditions to support artifacts. “A big part of the conservation process is to maintain a store or a display case that helps slow decay as much as possible,” said Bailey of the Smithsonian Museum of American Art.

The complex of measures may include ultraviolet filtering, which reduces accidental damage to the molecular bonds of plastic, which is not easy for a museum with a large number of windows. In order to preserve plastic works of art, it may also be necessary to maintain a low temperature and constant humidity, which reduces plasticizer migration, or provide an oxygen-free atmosphere to prevent oxidation.

Kollam with the team creates a special showcase for Armstrong's spacesuit with carefully selected conditions: 17 ºC, 30% humidity, and filters that remove pollutants. The Keepers hope that the showcase will be finished by next year, when the moon landing is 50 years old.

Even such a harmless action as cleaning an object for an exhibition can be a difficult process. For example, the task of cleaning the plasticizer from the surface seems to be quite simple, but cleaning causes the yield of even more plasticizer, which, in principle, accelerates degradation.

“The plasticizer is simply trying to find a balance between the outer and inner sides of the plastic,” Shoki said. “But as soon as the balance is broken, a catastrophe can happen.”

When observed through a polarizing filter on a plastic plate, traces of damage to the material are seen, diverging from the center, which allows us to understand exactly how this composition has degraded over time.

Regular dusting may scratch the soft surface of the plastic, ruining the clean and shiny finish. As an alternative, Shoki first applied the technology by which tiny microcrystals of dry ice, carbon dioxide snow, are sent in the form of jets to the plastic surface, collecting dust and other pollutants from it.

Despite its notoriety as the main polluter of the planet, plastic has a lot to do with the story. Even if we give up plastic, Shoki said, “I believe that there is a need to preserve this memory in human culture.”

He remembered the story of the tortoise shell and its plastic twin, cellulose acetate. “We managed to almost exterminate a certain type of turtles,” said Shocky, “but then we were able to move from natural material to alternative.”

“The fact that we use them instead of traditional materials has its own reasons,” said Janet Garcia, an expert in polymer chemistry from IBM. For the most part this is because the plastic is cheap and versatile, lightweight and durable.

Plastic bottles help transport water to remote locations, lightweight composite materials help save energy in cars and airplanes, disposable syringes and blood bags help prolong life. Prostheses replace the failing parts of the body.

“Partly thanks to the plastic we can experience our bodies,” says Madden. Not to mention sending people into space.

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