Romans Made Color-Changing Glass With Ancient Nanotechnology. Scientists Just Discovered How to Replicate the 1,600-Year-Old Marvel

Researchers were inspired by Lycurgus Cup, a chalice from the fourth century C.E. that appears opaque green under reflected light but wine red when lit directly. “To me, it’s magic,” the lead researcher says

Sarah Kuta | Daily Correspondent

October 28, 2026 8:30 a.m.

The Romans were ingenious inventors, developing everything from self-healing concrete that helped their structures stand for centuries to gravity-fed aqueducts that carried fresh water into cities. But one of their crowning achievements, at least in the eyes of some modern scientists, was developing color-changing glass that transformed from jade green to blood red in different lightings.

For decades, scientists have been inspired and intrigued by the Lycurgus Cup, a 1,600-year-old Roman chalice that’s been housed at the British Museum since 1958. In normal light, the cup is opaque green. But when light is shone directly thought it, it turns crimson.

Made during the fourth century C.E., the cup is decorated with mythological scenes from Homer’s Iliad, the epic poem set during the Trojan War. It shows Dionysus, the god of wine, punishing Lycurgus, the mortal Thracian king who opposed his worship, by ensnaring him in grape vines.

Now, researchers say they’ve figured out how to replicate this optical feat. “To me, it’s magic,” Lisa Hollands, a glass technical specialist at the University of Sheffield who led the work, tells the Guardian’s Dalya Alberge.

The Romans are believed to have created the cup’s color-changing effect by embedding tiny nanoparticles of silver and gold in the glass. Nanoparticles are much smaller than the wavelengths of visible light. Under certain conditions, they interact with light in ways that block some colors while allowing others to pass through.

“For this glass, if light is shone through it, the gold and silver particles block blue and green light, only allowing reds and oranges to pass through,” Hollands tells the Guardian. “If light is reflected off the surface, the particles have the effect of scattering the light, giving the opaque green color we see.”

Although scientists understood in principle how the Romans made their dichroic glass, reproducing the effect proved challenging, requiring lots of trial and error. “I accepted the challenge knowing that it might not work, as I knew it wasn’t as simple as embedding nanoparticles off the shelf into a glass,” Hollands tells Gizmodo’s Gayoung Lee.

First, Hollands teamed up with Caroline Jackson, an archaeologist and Roman glass expert at the University of Sheffield, to learn as much as she could about the materials. Together, they used modern materials to recreate a base glass similar to the kind the Romans would have made.

Then, Hollands tinkered around with various ingredients and processes—different furnace types, oxygen levels and materials, including sugar—until she came up with a recipe that consistently and repeatedly produced the desired effect with only the raw materials available to Roman artisans.

Ancient Secrets, Modern Light: The Lycurgus Project

The color of the glass was highly sensitive to small variations in the furnace. “If the glass went in a different position in the furnace, then the color came out differently,” Ian Freestone, an emeritus archaeological materials scholar at University College London, tells the Guardian.

He adds: “The fact that the color is so sensitive to the position in the furnace suggests that it would have been very difficult for the Romans to control the color. It makes me think that, with the Lycurgus glass, they hit the jackpot.”

Researchers created a version of dichroic glass in the 1960s. But Hollands’ glass is “more ambitious and more precise,” says Freestone, with colors that more closely match those of the Lycurgus Cup.

Did you know? Space-age glass

• In the 1960s, NASA revitalized the production of dichroic glass to protect astronauts and sensitive spacecraft technology from the harmful effects of unfiltered sunlight radiation in space.
• Instead of mixing metals into melted glass as the Romans likely did, scientists vaporized metals with electron beams and applied them to surfaces in an ultra-thin layer.

Following Hollands’ initial discovery, the researchers recruited British glass artist Elliot Walker to make a sculpture out of the color-changing glass. Walker’s glass sculpture draws inspiration from both the Lycurgus myth and the second-century Roman Farnese Atlas sculpture, which depicts Atlas holding up a celestial globe. In this case, Walker replaced the globe with a cup, a nod to the Lycurgus vessel.

“It is a very rare thing to have the opportunity to work with glass developed from ancient mixtures and recipes, and it is always a very exciting one,” he says in a statement. “You can really get an idea of how the glass makers of the past would have adapted to this sort of glass; it's like shaking their hands.”

Walker’s piece will be put on display at the University of Sheffield’s upcoming Festival of the Mind. After that, it will be exhibited permanently at the university’s Turner Museum of Glass.

Although the newly created dichroic glass is primarily decorative, the science behind it could have more practical applications. The research could help scientists develop new photonic materials, for example, or improve the use of glass to safely and permanently store radioactive waste via a process called vitrification.

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