by Hope Jahren
Ventilation and trapping are good strategies against cellulose acetate and cellulose nitrate, but the methods do not work on all plastics, Shashoua says. For example, when PVC breaks down, if its degradation products are pulled away from the surrounding environment, the plastic just releases more. Instead conservators need to keep PVC locked down, sealed in airtight containers, to stall its demise. When conservators noticed that the pristine white Apollo mission spacesuits were getting orangey brown stains on their nylon exterior, they realized the cause was plasticizer leaching out of life-support tubing made of PVC that had been sewn into the textile. The tubing kept astronauts’ bodies from overheating by circulating cooled water around the outfit. “We had to carefully remove all the life-support tubing from all the Apollo suits and store it separately in sealed containers,” Young says. “That was a lot of work.”
These opposing approaches—sealed containers versus ventilated ones—highlight why there is no one-size-fits-all solution. “No two objects are alike,” Strlič says. For this reason, conservation scientists try to identify the base polymer in a plastic artwork or artifact, typically with analytical machines such as a Fourier transform infrared spectrometer, which bounces long wavelengths of light off an object to reveal its unique molecular fingerprint. Conservators at the Solomon R. Guggenheim Museum in New York City used such a method to uncover a hidden danger in artwork by Bauhaus pioneer László Moholy-Nagy. They had believed the base material for his painting Tp2 was Bakelite (a phenol-formaldehyde resin), says Carol Stringari, head of conservation at the museum. But recent infrared spectrometer analysis by scientists affiliated with the Art Institute of Chicago revealed that the polymer was actually cellulose nitrate, one of the plastics that can release harmful gaseous acids.
Spectrometry used in this way is helpful, but it has limits. It can identify many ingredients, but it does not always show the entire potpourri of dyes, stabilizers, surfactants, plasticizers, and antioxidants that are mixed into plastics. Often industrial manufacturers keep these recipes secret as part of their intellectual property. Because there is no easy reference for their components, it requires arduous analysis to uncover the plastic’s chemical makeup.
These additives change the way an object will age and fall apart. Some varieties of PVC, such as the kind in the spacesuit’s life-support system, break down by leaching a sticky plasticizer called di(2-ethylhexyl) phthalate. Other PVC objects degrade by developing a white, powdery crust on the surface: in this case, stearic acid is to blame. It is a lubricant added to the plastic to prevent the polymer from sticking to its mold during the manufacturing process.
Sniffing Out Decay
It is so important to identify the chemical mélange before developing a life-extension strategy that researchers are literally sniffing out the ingredients in plastic artifacts. For example, in a project aptly named “Heritage Smells,” Katherine Curran of University College London capitalized on the fact that a lot of degrading plastics emit stinky molecules. Not only does cellulose acetate smell like vinegar as it breaks down, and aging neoprene like sickly sweet chlorine, but many other plastics also release volatile molecules as they disintegrate: degrading PVC has the aroma of a new car, and degrading polyurethane can smell like raspberry jam, cinnamon, or burning rubber. These are just the odors detectable by the human nose. Curran developed a mass spectrometry technique that analyzes all the volatile molecules rising off plastic objects to pinpoint the additives and stabilizers breaking down in a plastic. The goal is to identify what is going on inside without needing to take a sample and to do so before there are visible signs of decay, Curran says.
Curran took her technique to the Birmingham Museum & Art Gallery, where she sampled the air around an enormous art installation made in 2005 by Benin artist Romuald Hazoumé called ARTicle 14, Débrouille-Toi, Toi-Même! which translates to ARTicle 14, Straighten Yourself Out, by Yourself! It features a market cart full to the brim with sports shoes, computers, a film reel, golf clubs, old Nokia phones, toys, pots, pans, high-heeled pink shoes, and a vacuum cleaner, to name just a few components in the piece, which Hazoumé put together from objects he had collected during the 1990s and 2000s. Amid the chaotic artwork, Curran and her colleagues detected the presence of acetic acid, one of those corrosive gases that can hurt nearby materials. “We found that the film reel—specifically, degrading polyester in the film—was emitting the acid,” Curran says. Museum staff are now considering whether to store the film reel separately or use absorbents for the acid to prevent it from having a detrimental effect on other components of the piece, she says.
Curran has also tried out her canary-in-a-coal-mine technique at the Museum of London on a collection of vintage handbags—purses made of faux leather, mock tortoiseshell, or coiled 20th-century telephone cords. In the case of the white-telephone-cord purse, Curran sniffed out the presence of plasticizers that typically emerge from degrading PVC—a useful alarm bell for staff, who may want to store the purse in a sealed container.
Researchers are also turning to new imaging technologies that create detailed two-dimensional maps of the chemical composition of an object, essentially going pixel by adjoining pixel. For example, Strlič has combined near-infrared spectroscopy with a digital camera to produce two-dimensional colored maps from which conservators can identify the molecular makeup of artifacts that contain many types of plastic, as well as the migration of degradation chemicals. Strlič has gazed inside a popular vintage piece from the 1950s called a crinoline lady—where a plastic bust of a woman forms the handle of a hairbrush. Strlič’s team used the technique to identify the handle as cellulose acetate and the brush hair as nylon, using color gradients to show the location of the two plastics in the artifact. By identifying potential dangers such as the acetate, museum staff might be able to take action before damage is visible to the naked eye.
Although researchers are getting better at diagnosing how a plastic artifact or artwork is degrading, they are still trying to figure out how to best stop the decay and repair damage. That was one challenge tackled by a project called POPART, or the Preservation of Plastic ARTefacts in Museum Collections, which started in 2008 and combines efforts from institutions around the world. Cleaning may make the object look better, but it might eventually accelerate the overall demise. A white crust on the surface might be unsightly but is also a protective patina, similar to the green oxidized layer that forms over aged copper as both a degradation product and a protective skin.
Cleaning Up
Even if washing off this patina is the right strategy, POPART researchers want cleaning methods that can do so safely. Conservators are very cautious—a good characteristic in those charged with caring for million-dollar art. And plastics can get cracked, dissolved, or discolored when exposed to the wrong cleaning agent. POPART investigated approaches ranging from high-tech microfibers and ultrasound to carefully formulated cleaning microemulsions (solutions of water, oil, and a surfactant that lifts dirt), as well as gels. The scientists learned that cleaning a polystyrene object with acetone—often used in nail polish remover—could turn the plastic from transparent to opaque and eventually dissolve it. Isopropanol, a different alcohol-based cleaning solvent, however, is safe for most plastics.
Using something as simple as water to clean acrylic paintings turns out to be risky, says Bronwyn Ormsby, a conservation scientist at the Tate, a group of four museums in England. She confronted that problem with the 1962 painting Andromeda, the Tate’s oldest acrylic piece. Russian-American artist Alexander Liberman painted this abstract, geometric work on a circular canvas; its four solid colors—black, lilac, dark purple, and dark green—evoke the darkness of outer space. But acrylic paints have additives called surfactants that help to keep pigments suspended in the paint tube rather than settling to the bottom. That is good for the painter. Yet once on a dried canvas, these surfactants migrate to the surface and create a sticky substance that attracts dirt. By 2007 Andromeda was obscured by so much s
urfactant buildup that the painting had “a whitish bloom, which is quite distracting on paintings with dark colors,” Ormsby says. Ordinarily she would turn to water as a cleaner: “Water often removes soil better than any other solvent.” But water also makes acrylic paintings swell. That can lead to a loss of paint during the cleaning process.
Water can be tweaked to make it safer, though. Investigators led by Richard Wolbers of the University of Delaware have found that keeping water’s pH levels around 6 and making the water moderately salty can limit the swelling of acrylic paint. Ormsby used that technique on the Liberman painting, which today looks as dark and lonely as it did five decades ago. Researchers at the Tate have also used an atomic force microscope to monitor Warhol’s acrylic portrait of Brooke Hayward as it was cleaned, to make sure dirt and not paint was being removed.
Sustainable Art
Ormsby and others are also working with scientists at Dow Chemical to use the company’s industrial-scale abilities to run a large number of chemical reactions quickly to test a variety of microemulsions on acrylic paint samples. Their goal is to try different combinations of cleaning compounds to find the best formula for washing painting surfaces without harming them.
Plastics researchers are also reaching out to artists to let them know about the potential pitfalls of producing art from plastic. “The idea is not to interfere with the creative process but to allow the artists the option to use this information if they wish to,” says Carolien Coon, who is an artist herself, as well as a conservation scientist at the UCL Institute for Sustainable Heritage. Coon says she wonders about a sculpture she sold years ago that was made of silicone rubber, a bronze cast, a fishbowl, and baby oil. “I have no idea how it looks today. I hope it hasn’t leaked all over the dining room table.”
The great hope of conservation scientists is that restoring the past will also help them prepare for the future, when today’s plastic materials—such as 3D-printed objects—start entering museum collections. One such item might be the first 3D-printed acoustic guitar or a retired International Space Station suit. Eventually all will be past their prime, and conservators want to have the tools in hand to give these cultural icons a facelift.
MARIA KONNIKOVA
Altered Tastes
FROM The New Republic
The light in the room softly brightened and grew warmer, yellower, somehow more embracing. A quiet rustling—wind through leaves?—reached my ears. A white mist covered the table, carrying with it, somehow, the smell of damp earth after a late summer storm, and the promise of the mushrooms which would bloom in its wake. At the center of my table: a cylindrical terrarium-like enclosure filled with layers of soft green moss, soil, and broken branches, complete with a miniature tree. A plate was silently placed in front of me, or rather, a dark brown platform of what looked at first to be sod (actually a mixture of beetroot and mushroom powder with truffle), adorned with bursts of yellow pollen (a compact butter with truffle, root vegetables, and salt), anchored by a crinkled log (potato-starch paper covered in smoked salt, powdered mushroom, and porcini), punctuated by tiny green leaves (fig leaves), and at the bottom a thin layer of mushrooms (button, anchored by a mushroom stock jelly). Beneath all this theatricality was an undeniably delicious dish. Even today I recall its flavor and think of these as the best mushrooms I’ve ever eaten, though in fact I’ve consumed ones both more rare and more expensive. A map, which serves as a sort of menu for the Fat Duck, Heston Blumenthal’s three-starred Michelin restaurant in Bray, England—one of only four in the country—described this dish as “damping through the boroughgroves.” Presumably no mome raths would be consumed.
It was mid-October, and the Fat Duck, one of England’s best-known modernist restaurants, had just reopened after a nine-month hiatus and a $3.6 million redesign and reconceptualization. “It was time for a change,” the 49-year-old Blumenthal told me as we walked the restaurant. Blumenthal—one of the leading chefs in the world, a constant presence on global best-of culinary lists, and the host of several television shows in England—is a towering figure in his chef’s whites and thick, black-framed glasses, equal parts cook, linebacker, and fast-talking salesman. It’s difficult not to get swept up in his exuberance. Of course it was time for a change, and of course the changes were incredible. “We’d been going so fast for so long that we couldn’t keep up with all of these exciting advances happening outside the kitchen. It was time to rethink.” And so, while a pop-up carried on the restaurant’s name in Melbourne, Australia, Blumenthal and his team continued working, only instead of serving customers they invented new dishes, conducted experiments, and devoted themselves to creating a dining experience on the frontier of gastronomic science, a place where brain, body, and nutrition intersect.
The Fat Duck’s map wasn’t a menu in the traditional sense. It offered few clues to each dish’s contents, and the dishes themselves often appeared to be more Wonderland-like flights of whimsy than actual food. I was treated to Mock Turtle’s soup (complete with the White Rabbit’s gold watch); March Hare’s tea (the “itinerary” included with Blumenthal’s map reads, for this dish, “Excuse me, there seems to be a rabbit in my tea”); and a (literally) floating dessert concoction marked “counting sheep.” Lewis Carroll served as an inspiration, Blumenthal said, a means to stimulate the “fun” and “curiosity” that he feels should be part of any food experience. But the intention behind the food was quite serious. Blumenthal was trying to persuade people to engage with food in a fundamentally new way, one that is both physiological and emotional. “It’s not just about the food,” he said. “It’s the ebb and flow of the story, the look and feel of the room, the temperature, all that.”
The Fat Duck is operated along the principles of neurogastronomy, an emerging scientific field that examines how our sense of taste is interpreted and reinterpreted by the brain. The term itself was coined about a decade ago by Gordon Shepherd, a neurobiologist at Yale, who has been studying the science of olfaction for more than half a century. His research has shown that flavor, a complicated and little-understood concept, does not originate in what we eat but in what our minds derive from the experience. “Our sensory and motor appreciation of what we have in our mouth is created by the brain,” he said. “We can’t have gastronomy without it.”
This is the overarching principle that guides neurogastronomy: what we eat and why we eat it is as much a psychological phenomenon as a physical one. Throughout most of history, eating has been understood as a primitive human characteristic, an evolutionary necessity, the stuff of base survival instinct. This perception turns out to be far too simplistic. The more we learn about flavor, the more we realize just how easy it is to manipulate. Not just by the overclocked sensations of processed food, but in ways that make healthier choices seem at once tastier and more satisfying. Though most of us would like to think we have discerning palates, our taste is quite easy to fool.
When we try to imagine the flavor of something, we tend to focus on our mouth—the experience of placing, say, a ripe strawberry on our tongue. But that in fact is taste, and though we tend to conflate it with flavor, a vast chasm exists between the two. Taste is an experience composed of only five elements: sweet, salty, bitter, sour, and umami. Thousands of receptors on our tongue are designed to identify and respond to these elements, each one specializing in one of the five qualities. Without input from other senses—most notably our nose, but also our eyes, ears, and even hands—taste is merely a flat, single-note sensation with none of the nuance or enjoyment we associate with food in general and with specific foods in particular. Flavor is at once a broader and more powerful property than taste, one that marries the senses and their associate properties—memory, experience, neurobiology—to create and control the way we eat.
The promise that neurogastronomy holds is that once we understand how the mind combines the disparate biological and evocative forces that create flavor, we will be able to circumvent the learned and innate preferences o
f our taste buds. And with that capacity—truly an example of mind over matter—instead of stimulating appetite via the conventional and unhealthy trifecta of salt, sugar, and fat, we can employ the neural pathways through which flavor is constructed in the brain to divert attention to different, more nutritious foods. Control flavor and you control what we eat—and perhaps, given time and more research, begin fighting the global nutrition problems that are a direct result of the industrialized production of food.
Our preferences for salt, sugar, and fat evolved within the context of our species’ historical nutritional scarcity. These basic tastes are the echoes of prehistoric signals that saw humanity through epochs of less abundant food sources. They made sense when we were hunter-gatherers eating only what we could kill, less so when navigating the line at the local Subway. Indeed, our basic physiological response to taste is largely innate. Give an infant something sweet and she will lick it up. If it’s bitter, she will spit it out. (Bitterness signals potential poison.) We learn to like certain complex tastes over time, but our cravings for sweetness and fattiness remain constant. And so we continue to consume and store reserves for a hard winter that, today, never comes.
Ivan de Araujo, a neuroscientist at Yale Medical School who studies energy and reward in the brain, calls this the great conundrum of humans and food. “Why do we tend to violate homeostasis and equilibrium and eat more food than we need physiologically?” he asked me recently. “Why is there a bias in getting more energy than you’re going to expend?” The genetics of weight gain, psychological traits, and sensory perception of food are informed by these questions. When we attempt to address problems of global nutrition, we fight an uphill battle against the energy-craving and -storing machine that is the human body.
