Researchers at the University of Sheffield have reproduced the color-changing effect of the Lycurgus Cup, a fourth-century Roman vessel held by the British Museum since 1958. The roughly 1,600-year-old cup appears opaque green in reflected light but turns crimson when illuminated from behind so that light passes through it.
The effect is attributed to gold and silver nanoparticles embedded in the glass. These particles scatter reflected light, producing its green appearance; when light passes through, they block blue and green wavelengths while allowing reds and oranges to emerge. Although the underlying principle was understood, reproducing this dichroic glass reliably required extensive experimentation.
Project leader Lisa Hollands collaborated with archaeologist and Roman glass specialist Caroline Jackson to develop a base glass resembling the ancient material. Hollands then varied furnace types, oxygen levels and ingredients, including sugar, until she obtained consistent results using only raw materials available to Roman artisans. Even the glass's position within the furnace could alter its color. Archaeological materials scholar Ian Freestone said this sensitivity suggested that controlling the effect would have been difficult for Roman makers.
British artist Elliot Walker subsequently fashioned the glass into a sculpture drawing on the Lycurgus myth and the Roman Farnese Atlas sculpture. Whereas the ancient Atlas supports a celestial globe, Walker's figure holds a cup. The work will be shown at the university's Festival of the Mind before entering permanent display at its Turner Museum of Glass. Although primarily decorative, the new glass could also inform research into photonic materials and vitrification, a process for safely and permanently storing radioactive waste in glass.
