Scientists at the University of Sheffield have recreated the color-changing glass used in a 1,600-year-old Roman cup, developing a repeatable method for producing an effect that has puzzled glassmakers for centuries. The breakthrough reveals how ancient craftsmen may have created glass that appears green in reflected light but turns red when illuminated from behind.
The original artifact, known as the Lycurgus Cup, dates to the fourth century A.D. and is housed at the British Museum in London. It is one of about 40 surviving Roman cage cups and the only known example with this unusual optical effect.
How researchers recreated the ancient Roman glass
Dr. Lisa Hollands, a glass specialist with more than 25 years of experience, began the project after Christina Metcalfe, a university project manager, challenged her to reproduce the effect for Sheffield’s LightFest in 2025. Hollands worked with Roman glass expert Caroline Jackson to study ancient glassmaking techniques. They developed a base glass using modern materials that resembled those Roman craftsmen may have used.
The main challenge was adding tiny amounts of gold and silver to the glass in the right form. Scientists believe these metals form nanoparticles that interact with light, producing different colors depending on how the glass is illuminated. The Lycurgus Cup is considered an early example of Roman nanotechnology.
Scientists have recreated the mysterious color-changing glass of the 1,600-year-old Roman Lycurgus Cup. Using tiny gold and silver particles, researchers reproduced the ancient effect that makes the glass appear green in reflected light and ruby red when illuminated from behind. pic.twitter.com/CWE50uEDQx
— Tom Marvolo Riddle (@tom_riddle2025) October 27, 2026
“I knew that making a glass of this type was likely to be a complex task, as it is not just a case of adding nanoparticles to glass,” Hollands said. After extensive experimentation, Hollands developed a mixture that reproduced the cup’s distinctive colors. The achievement provides a repeatable manufacturing method, although researchers still do not know the exact process Roman glassmakers used.
An ancient Greek myth preserved in glass
The Lycurgus Cup features intricate carvings depicting Lycurgus, a mythical king of Thrace who angered Dionysus, the Greek god of wine. Dionysus frequently appeared in ancient Greek and Roman artwork. The scene shows the king trapped in vines, reflecting his punishment in Greek mythology.
Roman craftsmen carved the figures from a thick glass vessel, leaving delicate connections between the raised figures and the cup’s surface. The artifact reflects the technical sophistication of the ancient world, also seen in other remarkable ancient inventions.
Ancient glass inspires a modern sculpture
Following the successful experiments, the university commissioned British glass artist Elliot Walker, winner of Netflix’s “Blown Away” Season 2, to create a sculpture using Hollands’ glass. Walker combined elements of the Lycurgus myth with the Farnese Atlas sculpture, replacing its globe with a cup.
The sculpture will debut at Sheffield’s Millennium Gallery from Nov. 6 to 15, 2026, before moving to the university’s Turner Museum of Glass for permanent display.
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