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.
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 revolutionise 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 colours, 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.”
Today’s foams 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 mould 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.