Rome · 4th century AD · Sheffield, South Yorkshire, United Kingdom
Scientists recreate colour-changing glass of 1,600-year-old Roman Lycurgus Cup
University of Sheffield researchers grew gold and silver nanoparticles in glass that turns from jade green to ruby red, like the cup in the British Museum.
Sheffield, United Kingdom Scientists at the University of Sheffield have made glass that copies the colour change of the Lycurgus Cup, a Roman vessel of the fourth century AD. Like the 1,600-year-old original in the British Museum, the new glass looks jade green in ordinary light. Lit from behind, it turns ruby red.
The team worked from an ancient recipe derived from a fragment of the original Roman glass. This kind of glass is called dichroic, which means two-coloured. The Guardian reported the work as an exclusive.
Dr Lisa Hollands, a technician at the university's school of chemical, materials and biological engineering, carried out the replication. She called it "a labour of love" and said "people have tried it before with limited success".
To me, it's magic.
Dr Lisa Hollands, technician, University of Sheffield
Gold and silver particles grown in cooling glass
Hollands did the initial research with Prof Caroline Jackson, whom the Guardian describes as a leading Roman glass expert. The harder step was getting gold and silver nanoparticles into the glass. Each particle is a thousand times smaller than a grain of sand.
The team made a thick molten glass. As it cooled from well over 1,000C, gold and silver nanocrystals began to grow around particles within it.
Hollands explained the effect through the size of the particles. They are much smaller than the wavelengths of light. In certain conditions, she said, they block some colours because the light affects the electrons in their atoms.
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 colour we see.
Dr Lisa Hollands, technician, University of Sheffield
A colour that was hard to control in a Roman furnace
Ian Freestone, emeritus professor of archaeological materials at University College London, said a similar-coloured glass was made in the 1960s. He said Sheffield's version is much closer to the actual green and red shades of the cup.
This is more ambitious and more precise. I was excited because, for the first time, I was getting a feel of just how difficult it was to get these colours. This will help us understand how the Roman craftsmen actually worked.
Ian Freestone, emeritus professor of archaeological materials, University College London
Freestone said the colour depended heavily on conditions in the furnace. Glass placed in a different position came out a different colour. He thinks this would have made the colour very difficult for the Romans to control.
It makes me think that, with the Lycurgus glass, they hit the jackpot.
Ian Freestone, emeritus professor of archaeological materials, University College London
The cup carries a frieze carved in deep relief. It shows the god of wine, Dionysus, triumphing over King Lycurgus, who is caught in a vine. The Guardian traces the legend to the sixth book of Homer's Iliad. In 2022 an international panel named the cup one of the seven glass wonders of the world.
Freestone noted a theory that the red and green stand for the ripening of the grape. The scene shows vines pulling Lycurgus into the underworld. "So it could have been used in a drinking ceremony of some sort," he said.
A letter supposedly written by the emperor Hadrian to his brother-in-law in Rome mentions such vessels. It reads: "I have sent you parti-coloured cups that change colour, presented to me by the priest of a temple … I would like you to use them at banquets on feast days."
The university commissioned the glass artist Elliot Walker to use the effect in a new sculpture. It combines the Lycurgus story with the Farnese Atlas, with the globe replaced by a cup. "For me, it's a connection with the Roman makers," Walker said.
The sculpture will go on show at the Millennium Gallery during the university's Festival of the Mind, from 6 to 15 November. It will then go on permanent display at the Turner Museum of Glass.
Sources
- ‘It’s magic’: scientists rediscover how to make ancient Roman colour-changing glass (The Guardian: archaeology)
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