Solving a mystery that has puzzled experts for centuries, scientists at the University of Sheffield in England have recreated the color-changing properties of the British Museum’s storied 1,600-year-old Lycurgus Cup, which is green in typical lighting but turns red when lit from behind.
“To me, it’s magic,” Lisa Hollands, a technician who worked on project, told the Guardian. She added that “people have tried it before with limited success” and called the undertaking a “labor of love.”
The Roman cup, which was named one of the seven glass wonders of the world by the organizing committee behind the UN-designated International Year of Glass in 2022, bears a design that alludes to King Lycurgus from the sixth book of Homer’s Iliad. The design celebrates the triumph of Dionysus, the god of wine, over a vine-wrapped Lycurgus.
In their attempt to emulate the chameleonic quality of the vessel, the researchers embedded nanoparticles of gold and silver into glass—“each a thousand times smaller than a grain of sand,” as the Guardian described them.
Of the process, Hollands said, “So, 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. If light is reflected off the surface, the particles have the effect of scattering the light, giving the opaque green color we see.”
She also confessed: “If the Romans could have seen me experimenting, they’d probably laugh and ask: ‘Why does she not know how to make this?’”
A related sculpture by the glass artist Elliot Walker commissioned by the University of Sheffield will feature in the school’s Festival of the Mind in November before entering the collection of its Turner Museum of Glass.
Ian Freestone, emeritus professor of archaeological materials at University College London, suggested the green-to-red color change could relate to the ripening of a grape. “The depicted scene has grape vines pulling Lycurgus into the underworld,” he said. “So it could have been used in a drinking ceremony of some sort.”