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# Sheffield says it has reproduced the Lycurgus Cup's colour-changing glass
- URL: https://theromanfiles.com/sheffield-lycurgus-cup-colour-changing-glass/
- Published: 2026-10-26T13:27:30.000Z
- Updated: 2026-10-26T13:27:30.000Z
- Description: The University of Sheffield says a technician has reproduced the glass behind the Lycurgus Cup's green-to-red colour change. Here is what was made, and what experts believe the Romans did.
- Author: J E Cowie
- Tags: News

A Roman cup that is green when you look at it and red when you light it from behind has been a puzzle for glassmakers and historians for a long time. This week the University of Sheffield said one of its technicians has reproduced that glass. The Guardian ran the story on 25 October, and the university published its own release the next day.

![Map showing where University of Sheffield is](https://theromanfiles.com/content/images/2026/10/map_university-of-sheffield.jpg)

University of Sheffield, Sheffield, United Kingdom

## A cup that changes colour

The Lycurgus Cup is a 4th-century AD Roman artefact kept in the British Museum. It is made of "dichroic", or two-coloured, glass. In reflected light it looks jade green, and in transmitted light, with the lamp behind it, it looks ruby red. According to Sheffield, it is one of only 40 surviving glass cage cups from its period and one of the most complete. The university says it is the only one of them with this colour effect.

![The British Museum building, London, seen from the front](https://theromanfiles.com/content/images/2026/10/shot2_the-british-museum-building-london-seen-.jpg)

The British Museum, where the Lycurgus Cup is housed.

The scene on the cup is a story of punishment. Sheffield describes a mythical Thracian king ensnared in vines because of his misdeeds. The Guardian is more specific, placing the legend of King Lycurgus in the sixth book of Homer's Iliad and describing the triumph of the wine god Dionysus over him. In 2022, Sheffield says, an international panel of artists and conservators named the cup one of the seven glass wonders of the world.

## What the Sheffield team did

Sheffield's release says that no one knows exactly how the Romans produced the effect. Experts believe they added tiny amounts of gold and silver which, under the right conditions, formed layered nanoparticles thousands of times smaller than a grain of sand. Because the particles are smaller than the wavelengths of light, the release explains, they absorb light strongly and show colours that depend on their size and shape.

The work began when Christina Metcalfe, project manager of the Molecular Photonic Breadboards project, challenged the university's experts to replicate the cup's glass for LightFest in 2025\. Dr Lisa Hollands, a technician in the School of Chemical, Materials and Biological Engineering, took it on. She started from a recipe derived from a fragment of the original glass. She also worked with Professor Caroline Jackson, a Roman glass expert, to research what was already known about Roman glass, and then developed a base glass made from modern materials, intended to mimic what the Romans might have used.

The harder part, by Hollands's account, was getting small amounts of gold and silver into the glass in the right form. The release lists many experiments with different furnace types, starting materials and oxygen levels, and even the addition of sugar. The result was a glass that looked opaque green in reflected light and red with a light shone through it.

According to the Guardian, the glass was made thick and molten, and gold and silver nanocrystals began to grow around particles in it as it cooled from well over 1,000C. Hollands described the optics to the paper: "the gold and silver particles block blue and green light, only allowing reds and oranges to pass through." Light reflected off the surface is scattered instead, she said, "giving the opaque green colour we see."

Hollands called the work "a labour of love", and told the Guardian: "To me, it's magic." She also offered a guess at the Romans' view of her efforts: "If the Romans could have seen me experimenting, they'd probably laugh and ask: 'Why does she not know how to make this?'"

## How new is it?

Sheffield's release says the effect has been "reproduced in quantity for the first time in 1,600 years". The Guardian adds a qualification from Ian Freestone, an emeritus professor at University College London. He said a similar-coloured glass was replicated in the 1960s, but that Sheffield's is much closer to the cup's actual green and red shades. "This is more ambitious and more precise," he said.

Freestone also drew a lesson about the Romans. He said the colour depended on conditions in the furnace and changed with where the glass sat in it. That, he said, suggests it would have been very difficult for the Romans to control the colour, and "with the Lycurgus glass, they hit the jackpot."

My reading is that this is a demonstration that the effect can be made, which is a different thing from a record of how the Romans made it. The base glass was built from modern materials to mimic what the Romans might have used, and the release itself says that no one knows exactly how the Romans created the effect — adding gold and silver is what experts believe they did. Freestone's own comment is that the project will help us understand how Roman craftsmen actually worked.

## Why red and green?

Freestone told the Guardian of a theory that the two colours symbolised the ripening of the grape. The scene shows grape vines pulling Lycurgus into the underworld, he said, so the cup "could have been used in a drinking ceremony of some sort."

The Guardian also quotes a letter supposedly written by Hadrian to his brother-in-law in Rome: "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 paper says only that the letter was "supposedly" Hadrian's, and it does not say which cups he meant.

## The sculpture

The glass has already become an artwork. Sheffield commissioned Elliot Walker, a glass artist and winner of season two of Netflix's *Blown Away*, to make a contemporary sculpture from glass produced in the university's melting shop using Hollands's recipe. Walker said that working with glass from ancient recipes is "like shaking their hands". He described the piece as a blend of the Lycurgus story and the Farnese Atlas sculpture, with the globe replaced by a cup.

The university says the sculpture will be unveiled at the Millennium Gallery during the university's Festival of the Mind, which runs from 6 to 15 November 2026\. After that it will go on permanent display at the Turner Museum of Glass in the School of Chemical, Materials and Biological Engineering.

## Beyond the museum

Sheffield says this particular glass will mainly be decorative, but that the scientific understanding gained will feed into new photonic materials and into advanced glasses for radioactive waste management. The project is linked to Professor Russell Hand's work in the university's Immobilisation Science Laboratory on immobilising complex nuclear wastes in glass.

## Sources

The Guardian (2026) '‘It’s magic’: scientists rediscover how to make ancient Roman colour-changing glass', The Guardian, 25 October 2026, available at: [https://www.theguardian.com/science/2026/oct/25/scientists-rediscover-ancient-roman-colour-changing-glass](https://www.theguardian.com/science/2026/oct/25/scientists-rediscover-ancient-roman-colour-changing-glass?ref=theromanfiles.com) (Accessed: 26 October 2026).

University of Sheffield (2026) 'Technician cracks 1,600-year-old mystery to replicate Roman masterpiece', The University of Sheffield, 26 October 2026, available at: [https://sheffield.ac.uk/news/technician-cracks-1600-year-old-mystery-replicate-roman-masterpiece](https://sheffield.ac.uk/news/technician-cracks-1600-year-old-mystery-replicate-roman-masterpiece?ref=theromanfiles.com) (Accessed: 26 October 2026).

## Picture credits

- Top picture: The Lycurgus Cup, a Roman glass cup of the 4th century AD. Photo: Vassil, via [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:British%5FMuseum%5FThe%5FLycurgus%5FCup%5F01%5F15022019%5F4376.jpg?ref=theromanfiles.com) ([CC0](https://creativecommons.org/publicdomain/zero/1.0/?ref=theromanfiles.com))
- The British Museum, where the Lycurgus Cup is housed. Image: British Museum front facade, by Death Star Central, via [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:British%5FMuseum%5FFront%5FFacade.jpg?ref=theromanfiles.com) ([CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/?ref=theromanfiles.com))
- Map: drawn from [Natural Earth](https://www.naturalearthdata.com/?ref=theromanfiles.com) (public domain) and [Wikidata](https://www.wikidata.org/wiki/Q823917?ref=theromanfiles.com).