PREVIEW

BY MARK WORGAN

A University of Sheffield technician has discovered the secret of the Romans’ incredible colour-changing glass after it remained lost for 1,600 years.

The Lycurgus Cup, a world-renowned fourth-century AD artefact housed at the British Museum, is made from ‘dichroic’ glass that appears jade green in reflected light and ruby red when light passes through it.

Depending on the position of the light source, the cup can therefore appear in two strikingly contrasting colours.

It is one of only 40 surviving Roman glass cage cups from the period and is among the most complete. However, the Lycurgus Cup is the only known example to display this extraordinary visual effect.

Its colours, craftsmanship and near-perfect condition have fascinated and perplexed historians and glassmakers for centuries. In 2022, an international panel of artists and conservators recognised it as one of the seven glass wonders of the world, citing its exceptional colours and the story depicted on its surface: that of Lycurgus, a mythical Thracian king ensnared in vines as punishment for his misdeeds.

Although the precise method used to create the cup’s colour-changing effect remains unknown, experts believe the Romans added tiny quantities of gold and silver to the glass. Under the right conditions, these metals formed layered nanoparticles thousands of times smaller than a grain of sand. These particles interact strongly with light, producing vivid colours depending on their size and shape.

Numerous attempts have been made to reproduce the dichroic effect. However, developing a reliable, repeatable recipe has long proved elusive - until now.

Challenged by project manager Christina Metcalfe to recreate the effect, Dr Lisa Hollands and her colleagues have now succeeded in producing glass that displays the same striking colour change.

For Dr Hollands, a technician at the University’s School of Chemical, Materials and Biological Engineering, the work was a labour of love.

“I knew that making a glass of this type was likely to be a complex task, as it is not just a case of adding nanoparticles to glass,” said Dr Hollands.

“I’ve studied and worked with glass for over 25 years, so I used the knowledge and experience I’ve gained, coupled with a modern scientific understanding of what I was trying to achieve.

“To start with, I worked with a leading Roman glass expert, Professor Caroline Jackson, to research what was already known about glass of the time and developed a base glass using modern materials to mimic what the Romans might have used. Then came the more difficult part of trying to get small amounts of gold and silver into the glass in the right form.

“Although if the Romans could have seen me experimenting, they’d probably laugh and ask: 'Why does she not know how to make this?'”
After numerous painstaking experiments involving different types of furnace, starting materials and oxygen levels — and even the addition of sugar — Dr Hollands finally developed a recipe that produced glass which appeared opaque green in reflected light and red when illuminated from behind.

The next stage was to create a sculpture worthy of the ancient original.

Molecular Photonic Breadboards project manager Christina Metcalfe said: “We approached Elliot Walker, one of the UK’s finest glass artists and winner of season two of Netflix’s Blown Away, who accepted the challenge and was commissioned to create a contemporary sculpture using Dr Hollands’ recipe.”

Elliot added: “It is a very rare thing to have the opportunity to work with glass developed from ancient mixtures and recipes, and it is always a very exciting one.

“You can really get an idea of how the glass makers of the past would have adapted to this sort of glass; it's like shaking their hands.”
The idea of bridging the centuries, alongside practical considerations, helped shape the final design.

“I wanted to keep the sculpture quite classical in form and to carry through the original story of Lycurgus shown on the cup, but we needed a blown element within this to really show the dichroic glass,” Elliot added.

“The piece is a blend of the Lycurgus story and the Farnese Atlas sculpture, with the globe replaced by a cup.”

The sculpture will be unveiled to the public at Sheffield’s Millennium Gallery as part of the University’s Festival of the Mind from 6 to 15 November 2026.

It will then go on permanent display at the Turner Museum of Glass, based in the School of Chemical, Materials and Biological Engineering.

“We set out to create something tangible to help the public understand what is possible when these tiny nanoparticles are embedded in something,” Christina added.

“What Lisa and Elliot have managed to achieve has surpassed all our expectations. The incredible historic narrative really captures people’s imaginations, and I like to think we’ve created something that people will marvel at for years to come.”

Although the recreated glass is expected to have mainly decorative applications, the scientific knowledge gained could help inform the development of new photonic materials and advanced glasses for radioactive waste management.