Researchers at the University of Sheffield have reproduced the striking optical effect of the Lycurgus Cup, a Roman vessel made around 1,600 years ago. Dating from the fourth century and held by the British Museum since 1958, it appears opaque green in reflected light but red when illuminated from behind.
The effect is thought to result from gold and silver nanoparticles embedded in the glass. These particles block blue and green light while allowing red and orange wavelengths to pass through. At the surface, they scatter reflected light, creating the cup's green appearance.
Led by glass specialist Lisa Hollands, the project began with a collaboration with Caroline Jackson, an archaeologist specialising in Roman glass. After recreating a comparable base glass, Hollands experimented with ingredients, furnace types and oxygen levels until she established a repeatable recipe using only raw materials available to Roman craftspeople. The resulting colour was highly sensitive even to the glass's position within the furnace.
Although researchers produced colour-changing glass in the 1960s, archaeological materials scholar Ian Freestone describes Hollands' version as more precise, with colours closer to those of the ancient cup. The original vessel depicts the punishment of King Lycurgus by Dionysus, the god of wine.
British glass artist Elliot Walker has transformed the new material into a sculpture drawing on that myth and the Roman Farnese Atlas sculpture. Whereas the ancient Atlas supports a celestial globe, Walker's figure holds a cup. His work will appear at the University of Sheffield's Festival of the Mind before being exhibited permanently at the university's Turner Museum of Glass.
