Last year, Lauren Bowker was halfway through a nostalgic re-watching of the cult ’90s teen film The Craft when the idea struck. More specifically, it was during the “glamor spells” scene, when Robin Tunney’s character goes from brunette to platinum blond just by combing her fingers through her hair. “It was in that moment that the penny kind of dropped,” says Bowker, “I was like, ‘We could do that.'”

That wasn’t posturing: As a chemist, fashion designer, and the founder of the London-based material design studio, The Unseen, Bowker is something of a high-fashion alchemist. Her color-changing leather purses and otherworldly wearable Air sculptures are a measured mix of stunning aesthetics and seriously complex science.

Today The Unseen is releasing color-changing hair dye that’s exactly as magical as it sounds: With a sharp temperature change, the dye shifts hues on its own, as if spellbound.

One dye changes from black to crimson, with a tint of fire-y orange, when you blush.

Bowker and her team have come up with seven different semi-permanent hair dyes, each with its own unique reaction to either bodily or environmental temperatures. There’s one that changes from black to crimson, with a tint of fire-y orange, when you blush—or your body temperature rises. “It will change if you get embarrassed, or if there’s someone in the room you fancy,” says Bowker. There’s a white blond that changes to an ice-y blue when you go outside on a chilly day (temperatures below 60 degrees Fahrenheit). Others change from a silvery grey to pastel pink, or move from red to green to blue. In collaboration with the U.K.-based Storm Models, the Unseen is launching the project at London Fashion Week with a series of videos that showcase the technology.

The Unseen plans on partnering with a cosmetics company to bring the dyes to market, but for the time being the project will fit right in with a fashion world that’s in the midst of a color-saturated ’90s throwback. In fact, Bowker used much of the same science behind Hypercolor T-shirts, a favorite gimmick of the decade, to develop the dyes. The science of the hair dye boils down to a complex carbon-based molecule that undergoes a reversible reaction with itself. The scientists in Bowker’s lab manipulated the chemical bonds in the dyes so that above certain temperatures one of the molecules forms is more stable than the other, causing a reaction to take place. The result is a molecule with a slightly different absorption of light, which makes it appear as a different color. Although the dye does contain some toxic ingredients—every hair dye does—the lab was careful to reduce them, and used polymers to ensure that the dye wouldn’t irritate the scalp. The dye is also temporary, and comes out after a few washes.

Like all of The Unseen products and fashion collections, the hair dyes are an eye-catching, consumer-facing product that demonstrate some of the harder science the company is doing behind the scenes. A lot of The Unseen’s R&D work is in the health sector, and isn’t yet public. Bowker says that they were researching how the body responds to extreme heat and cold, and the ways we can detect its discomfort, when they started experimenting with the hair dye. While she can’t say what this research was for, she says it’s the kind of materials science that might be useful for designing better military gear, for example, or even normal sportswear.

But it turns out her findings were also useful for making witch-y hair dye as mutable as teenage mood swings. Bowker is hoping that by showing the creative aspects of science, more young people—and particularly teen and pre-teen girls—will be interested in entering the field. “Modern witchcraft and modern alchemy is possible,” she says. “All the sort of sci-fi visions from 15 years ago”—or 20, in the case of The Craft—”can now be true.”

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