Thanks to Physics, This Chocolate Is Iridescent—and Safe to Eat

Jun 14, 2023

One Twitter user and Swiss researchers have created chocolate that diffracts light like a prism

Nora McGreevy

Correspondent

Those familiar with chocolate will recognize it in many flavors, from milk to extra dark, and in many forms, from syrup to bunny. But recently, Samy Kamkar debuted his take on this age-old treat: iridescent chocolate that glimmers like a rainbow.

The shimmery sweet looks like something out of Willy Wonka's universe—but this one comes with no side effects, as Devi Lockwood reports for the New York Times. Its surface has lots of miniscule grooves that diffract light like a prism, giving the chocolate's surface that mesmerizing sheen, Kamkar explains.

I’m finally getting some decent results producing 100%-edible iridescent tempered chocolate. The colors are from the chocolate (not any ingredient or coating) diffracting light after being forcefully molded onto a diffraction grating in vacuum. pic.twitter.com/6wpbsIKh5C

Kamkar founded the internet security company Openpath and likes to tinker with his food in his spare time, he says. "Anyone can do this at home," he tells the Times. "There's no coating. There's no special ingredient. It's the surface texture of the chocolate itself that's producing it."

Anyone who has a 3-D printer, that is. To make the chocolate, Kamkar created a mushroom-shaped mold with multiple ridges micrometers apart. He tempered the chocolate, poured it into the mold and then put it in a vacuum chamber to prevent air bubbles on the surface. (He chose a mushroom shape because they’re "magical," he tells the Times.)

As Marnie Shure reports for the Takeout, Kamkar posted a video of his creation to Twitter on May 9, where users were fascinated with his success.

As Renusha Indralingam explained in Yale Scientific in 2013, iridescence occurs "when an object's physical structure causes light waves to combine with one another, a phenomenon known as interference." In the natural world, hummingbirds, beetles, butterflies, peacocks and many other living organisms exhibit iridescent traits, which they can use to choose and attract mates or evade predators, Indralingam wrote.

Kamkar's idea isn't new. In December, researchers at ETH Zurich and the University of Applied Sciences and Arts Northwestern Switzerland announced that they had filed a patent for the process of making shimmery, iridescent chocolate without additives, per a statement. The scientists said they were in talks with major chocolate producers about scaling up their discovery for commercial use.

Patrick Rühs, a scientist involved in that project, tells the Times that one of the biggest problems they face will be convincing consumers that the chocolate is safe to eat, reflective surface and all. "Maybe the surface is actually too shiny. […] People think that there is a plastic foil on top, which is not the case," he says.

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Nora McGreevy is a former daily correspondent for Smithsonian. She is also a freelance journalist based in Chicago whose work has appeared in Wired, Washingtonian, the Boston Globe, South Bend Tribune, the New York Times and more. She can be reached through her website, noramcgreevy.com.