Many components of modern shoes are made of plastic materials, from the soles to the uppers to the eyelets.
GIF by Hannah Whitaker, National Geographic
Most of those shoes are partly, or in many cases completely, fabricated from plastic and plastic-like materials, from the squishy soles to the pointy heels to the knit polyester uppers to the brittle eyelet holes. Because of their construction—usually, their many components are stitched and glued and molded together in complicated ways—they’re almost impossible to recycle. So your feet are only a short stopover in their long, long lifetimes, before they pile up in landfills and float down waterways, often
living on like zombies for hundreds of years.
The first stirrings of a shoe revolution are fomenting, though, and the industry is starting to look hard at the ways it can build a better, more sustainable mousetrap for your feet. But to understand how big of a challenge that is, we have to understand how we ended up in a world where most shoes are a soft, squishy mess of plastics.
Shoes for leisure, shoes for sports
Until the middle of the 1800s, shoes were made from materials found in the natural world. Wood for heels.
Tanned leathers for uppers and straps. Soles were rubber, or cork, or sometimes hunks of wood carved to cradle a foot. But shifting culture and materials science were coming for shoes, as they came for everything else.
In the late 1800s, factory labor emerged as a dominant work type in Europe and the U.S. Once a year, usually in the summer, the factories had to close down for repairs, releasing a flood of workers out into the world, many of whom flocked to the seaside. This was the first glimpse of modern “vacations,” a new kind of leisure time that required a new suite of accessories. Instead of work boots, vacationers wanted light shoes that could withstand the damp of the beach.
Around the same time, sports and leisure culture was developing. Croquet players in England wanted sticky soles to keep them steady as they aimed at their wickets. Lawn tennis players needed shoes that wouldn’t slip on close-shorn turf.
The solution? Rubber. A new chemical process that kept rubber stable at warm temperatures, called “vulcanization,” was invented in the middle of the 1800s. That stable rubber material quickly made its way
into tires, as seals on steam engines—and onto the soles of shoes for the athletes and vacationers of the time.
“The most significant development in shoe technology in the last century was vulcanized rubber,” said
Nicholas Smith, the author of a Kicks, a book about the cultural history of sneakers.
The original vulcanized rubber wasn’t what we now think of as plastic. But by the middle of the 20th century, “natural” rubber products had been replaced nearly wholesale by
synthetic rubbers—a close relative of the materials we know as plastics. Today, about 70 percent of all rubber used in manufacturing is synthetic, according to the American Chemical Society.
With the rise of rubber and leisure time—and along with it, sports like running and basketball—came a cry from athletes and shoe designers for more cushioning, more springiness, more support, less stretch. By the first few decades of the 1900s, the market for athletic shoes exploded and designs multiplied.
Shoes for fantasies and fashion
“Fashion is a thing that often drives innovation. It’s a product of desire and design,” says
Elizabeth Semmelhack, the curator of the Bata Shoe Museum in Toronto. “The capabilities of this new material to augment design pushed fashion forward, and vice versa.”
As hemlines rose in the early 20
th century, shoes—which had often been hidden under long skirts—became a part of the visual language of women’s fashion. In the 1920s, Jazz Age tastes for embellishment and sparkle were answered by plastics, from t-straps covered with fake crystals (themselves often made of plastic) to ultra-shiny celluloid finishes on evening shoes.
Simultaneously, women started entering the American workforce en masse, a movement that only grew during war times and beyond.
“These were really interesting cultural moments, when women were starting to make their own money and buy more clothes and to become more trend aware,” says
Marie Brennan, a design historian at Norwich University and shoemaker. The variety and sheer number of shoes being bought for fashion, rather than purely practical purposes, grew.
Plastics were making it easier and cheaper to fill that new market.
By World War II, high heels had taken on strong symbolic power, says Semmelhack. U.S. soldiers serving abroad latched on to heels as a sign of idealized femininity, hanging posters of pin-up girls in sky-high heels and painting stilettoed women on the sides of their
fighter planes. At home, most heeled shoes tended to be platforms or wedges made with natural bases. But those styles were not popular with the soldiers.
“When the war was over, the platforms and wedges got thrown out, and that era of wartime fashion ended for women,” says Semmelhack. “Fashion sought to align women with the erotic ideals of how women were presented during the war effort. So the high heel returned with a vengeance in the postwar period.”
The practical problem with high heels was technical. The heel spike had to support essentially the entire weight of the wearer. Steel worked, but it was expensive and heavy. Wood wasn’t strong enough. But new ultrahard thermoplastics were, and they could be coated with leather—and later, vinyls—to hide the ugly interior.
Designers drove a subsequent explosion in the quality and types of synthetic materials available. Among them, Ferragamo designed wedges based on Bakelite and
sandals that used wide strips of Nylon for the uppers, and Roger Vivier sold clear plastic booties to fashionable clients. Seventies-era disco-goers could buy sky-high platforms; one design incorporated little fishbowls in the heels.
Newly unfettered by design limitations, shoes began to reflect the culture around them, including the 1960s obsession with the clear materials and plastics that were driving the space race at the time, says Semmelhenk.
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And the rise of skate culture in the western U.S. in the 1960s and 70s—driven in part by a spate of droughts that forced homeowners to drain their backyard pools—was nudged forward by new ways of building shoes that could withstand a skateboarder’s beatings.
Athletes: ‘more performance!’
Simultaneously, worldwide sports culture was exploding. Running records were being set at every new world championships and Olympics, and companies like Adidas and Nike fought to get the top athletes to wear their cutting-edge designs. The same thing was happening on the basketball court.
Athletes wanted shoes that wouldn’t stretch, and they wanted shoes that would give them whatever little bit of a boost they could get. Rubber soles weren’t going to cut it, and leather uppers flexed too much.
“Leather is flesh,” says Edwards. “It’s always going to move with a body.”
In 1972, Nikes dropped the “Cortez” sneaker—a new design for runners that they promised would revolutionize the experience. They added a foam layer between the outsole and midsole made from “Phylon,” a composite of little ethylene vinyl acetate foam pellets that were heated and then cooled into a soft foam wedge. The squishy, springy foam sole was born.
Around the same time, designers got excited about using leather look-alikes for the uppers. Those materials were usually made from polyvinyl, a type of plastic. Players liked that they were flexible like leather but deformed less. Designers liked that they could produce a much wider range of colors, textures, and finishes than they could with natural leathers.
From then on, springy foam technologies and vinyl-esque uppers became the name of the game. Companies hired squadrons of designers and materials scientists to tweak the chemistry or shape of their materials to eke out a tiny bit of color from the upper, or extra energy returned to the runner from the soles.
“It was the obvious thing to do,” says Edwards. “You got improved strength, visual options, and easier production.”
kick about 70 percent more energy back at their wearers than the proto-foams of the 1970s; many runners think it translates to a noticeable increase in speed, though the science is still out on that. No matter what, new technologies have changed the way feet move and running motions develop. Some scientists and athletes think that technology like energy return foams were critical in Eliud Kipchoge’s sub- 2-hour marathon record last week.
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Shoes for the future
Plastics and plastic-like substances have completely reshaped the footwear landscape, says
Nicoline van Enter, an expert on shoe design who focuses on sustainability issues. They’ve made shoes better, lighter, faster, more comfortable, and more accessible to foot-havers worldwide. So the big question now is: Can they also be made in a way that uses less planet-choking plastic?
Some shoe companies are looking to the past to excise plastic.
Sevilla Smith, for example, builds each pair from only natural materials—strips of leather, wood, and metal nails—designing each shoe with the minimum of materials so they can be resoled or repaired nearly indefinitely.
The current trend in athletic footwear design, says van Enter, is less, less, less: Think Nike Flyknits, with their stretchy knit uppers. That slimmed-down design, says Edwards, is partly inspired by aesthetics, but also by economics, because it’s much cheaper to make a shoe that requires fewer pieces to glue or sew together.
That design also offers an interesting opportunity, says van Enter. Any shoe that uses mixed materials is tricky, if not impossible, to recycle, she says. So a shoe that uses only one material offers at least some hope of being recycled eventually.
Adidas is working on making a shoe that fits these principles. Their “Futurecraft Loop” sneaker, in development now, is made of one single material (thermoplastic polyeurethane) that can be at least partly recycled. Simultaneously, they and other brands are making shoes out of recycled ocean plastics.
But the limits of plastic recycling are currently hard. It takes energy to collect the materials, remake them into their second existence—and in many cases, that second life is their last, so recycling extends the process but doesn’t solve the underlying problem.
The solution? “We’re just going to have to buy and consume a lot less,” says Brennan.
Or, maybe, the future looks stranger. Edwards, laughing, explains his dream about the shoe of the future: A liquid material you’d dip your feet into when you leave the house each day, making a perfect mold of your foot. Then, when you come home, you dip your feet into another thing that breaks down the “shoe,” recycling it and getting it ready for the next day. It’s a dream for now, but creative solutions will be necessary if we’re going to kick our plastic habit.