University of Sheffield researchers recreate ancient Roman dichroic glass

Researchers from the University of Sheffield have successfully reproduced the ancient Roman recipe for dichroic glass, a technique used to create the 4th-century Lycurgus Cup currently held in the British Museum. The glass is famous for its ability to change color from jade green to ruby red depending on how it is illuminated.

By analyzing a fragment of the original artifact, researchers Lisa Hollands and Caroline Jackson determined that the effect is caused by tiny nanoparticles of gold and silver. These particles, which are thousands of times smaller than a grain of sand, interact with light wavelengths to create the shifting colors. The team achieved this by melting glass at temperatures exceeding 1,000°C and carefully controlling the cooling process to allow nanocrystals to form.

The breakthrough has been used to create a contemporary glass sculpture by artist Elliot Walker, intended for the 2025 Sheffield Light Festival.