In the early 1960s, curators at the Philadelphia Museum of Art noticed something funny about one of their modern-art sculptures: It smelled like vinegar. Worse, the once-clear plastic sculpture had begun browning like an apple, and cracks had appeared on its surface. By 1967, Naum Gabo's translucent, airy Construction in Space: Two Cones looked like Tupperware that had gone through the dishwasher too often.
The volatile Gabo got so angry at the curators (he blamed the deterioration on their keeping his work in an airtight display case) that he took the sculpture back to repair it. That didn't work—things, in fact, got worse—and he finally gave up. He cast a replica of Two Cones, donated it to the Tate in London, and gave Philly back the degraded original.
The incident would have remained a footnote in art history, except that other Gabo pieces (including the Tate's replica) started falling apart, too, and in much the same way. They flaked into pieces, turned strange colors, and began to reek. Gabo found a reason to blame other owners for mishandling his work, but curators soon discovered a common factor: rhodoid, an early plastic made of cellulose acetate.
In the 1920s, Gabo and other artists began experimenting with plastic, both because it offered the freedom to create any shape in any color and because they believed artists should embrace technology and a plastics-based industrial future. (Gabo was trained as an engineer.) Plastics manufacturers assured the artists that cellulose acetate was durable—Greek marble for a new generation. Not quite. It turned out plastics were no more intrinsically stable (and sometimes less stable) than wood, paint, or any other media—a detail Gabo and the Philadelphia curators never suspected until too late.
The problem of preserving plastics isn't limited to highbrow art. Not long after The Graduate debuted, manufacturers around the world began to incorporate synthetic polymers into their goods. As plastics revolutionized the making of furniture, toys, health care products, and electronics, museums of industry, design, and medicine began snapping up plastic objects that were either historic (the first artificial heart) or culturally important (Barbie dolls). Plastics hold up well for the decade or so during which a consumer uses most products. But museums, unlike consumers, are in it for the long haul, and when plastics crash, they crash precipitously. As a result, museums of all sorts have been having Gabo moments in the past decade.
The casualty list is appalling: Antique plastic dolls at the National Museum of Denmark have begun to peel and flake; classic furniture at the Victoria & Albert Museum in London might as well have been left out in the sun for years; the first-ever plastic toothbrush, at the Smithsonian, is collapsing into a pile of crumbs; etc. A whole generation of irreplaceable items that are as representative of our culture as pottery or flintheads were of ancient ones are dying—and many people charged with their care have no idea how to stop further damage.
A handful of unstable, "malignant" plastics are responsible for most of the carnage. Cellulose nitrate was the first widely used plastic (it dates to the early 1830s); it was used to make the film in reel-to-reels. It's remembered today for being a notorious fire hazard: Billiard balls made of cellulose nitrate would occasionally explode on contact, and the plastic was responsible for the destruction of many early movie theaters, as hot projection booths caused the film to catch fire. For safety reasons, cellulose acetate, the material Gabo used, began to replace cellulose nitrate in many applications in the 1930s, though it wasn't any more durable. Because both plastics were based on readily available plant matter (cellulose is the main component of a plant's cell walls), they found widespread use until the 1970s, despite their flaws.
More recently, manufacturers and artists have turned to latex and wholly synthetic plastics like PVC or polyurethane. But these plastics have also proved feeble over the long term. At a molecular level, plastics are long chains of a single molecule repeated over and over. Such long chains would be uselessly brittle on their own, but chemists realized they could add chemicals, called "plasticizers," whose molecules work their way between the chains and soften the plastics up. This greatly increased malleability, and virtually all plastics today employ plasticizers. Unfortunately, plastics will squeeze the plasticizers out over time. This process pushes the chemicals to the surface of the object, leaving the underlying plastic fragile. Different plastics deteriorate in different ways under different conditions, depending on what plasticizers or dyes were added. But the end result tends to be forms of matter rarely seen outside the reject piles of industrial chemistry labs. You can recognize "bleeding" or "weeping" plastics by the slimy plasticizers pooling on their surfaces. Other plastics push powder to their surfaces and feel sugary to the touch.
Scientists have struggled to figure out the best general strategy for the long-term care of plastic objects. One necessary step is keeping them out of sunlight, since ultraviolet light breaks down both plastic fibers and the colored pigments in plastics, bleaching them. Curators also need to watch out for biological agents. Molds and bacteria have evolved to eat plastics, and although it's not their preferred food, some beetles will eat through Plexiglas if hungry enough.