Top view of the famed Lycurgus Cup in
the British Museum, showing the glass both green and ruby red. Credit:
Chappsnet/Wikimedia Commons, CC BY
The
Lycurgus Cup, a
world-renowned 4th-century A.D. artifact housed in the British Museum, is
constructed of "dichroic" glass that shifts from jade green in
reflected light to ruby red in transmitted light. This means that depending on
where the light source is positioned, observers can see the cup displayed in
two distinctive, contrasting colors.
It is one of only 40 surviving glass
cage cups from the period and is one of the most complete. The Lycurgus Cup is
the only one exhibiting this visual effect. Its colors, artistry and almost
perfect condition have intrigued and confounded historians and glassmakers
alike for centuries. Its exceptional colors and narrative, depicting a mythical
Thracian king ensnared in vines because of his misdeeds, led to the artifact
being recognized as one of the seven glass wonders of the world by an
international panel of artists and conservators in 2022.
While no one knows exactly how its
famous color-changing effect was created, experts believe the Romans achieved
it by adding tiny amounts of gold and silver which, under the right conditions,
formed layered nanoparticles thousands of times smaller than a grain of sand.
Because these nanoparticles are smaller than the wavelengths of light, they
absorb light strongly and display vibrant colors depending on their size and
shape.
Many have tried to reproduce this
dichroic effect with varying success, but establishing a consistent, repeatable
recipe has long proved elusive.
After being challenged by project manager Christina Metcalfe to replicate it for the university's LightFest in 2025, experts from the University of Sheffield have successfully reproduced the effect observed in the famous artifact, finally solving the age-old mystery.
Credit: David Heath, University of Sheffield
Recreating the Roman glass recipe
For University of Sheffield
technician Dr. Lisa Hollands, replicating the effect was very much a labor 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 Hollands, from the University of Sheffield's
School of Chemical, Materials and Biological Engineering.
"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 many painstaking experiments with different furnace types, starting materials and oxygen levels—and even the inclusion of sugar—Hollands finally hit upon a glass recipe that appeared opaque green in reflected light and red when a light was shone through it.
Dichroic glass cup created by University
of Sheffield technician Lisa Hollands. Credit: Ed Cartledge, Sort of Films
An ancient recipe becomes contemporary sculpture
The initial piece was exhibited at LightFest, an event held in Sheffield by the Molecular Photonic
Breadboards project in partnership with the universities of Sheffield and
Bristol. The project aims to design new materials that harness the power of
light for sustainable technologies, vital to the U.K.'s economic success in
areas like solar energy, quantum technologies and health care diagnostics.
Molecular Photonic Breadboards
project manager Metcalfe said, "The next step was to commission a piece
worthy of paying homage to its illustrious predecessor.
"We approached Elliot Walker,
one of the U.K.'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 Hollands' recipe."
Walker said, "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 glassmakers of the past would have adapted to this sort of glass; it's
like shaking their hands."
This idea of a bridge between the
intervening centuries, along with practical considerations, provided the
inspiration for the final piece.
"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," Walker added.
"The piece is a blend of the
Lycurgus story and the Farnese Atlas sculpture, with the globe replaced by a
cup."
A public debut and lasting applications
The piece will be unveiled to the
public at the Millennium Gallery as part of the university's Festival
of the Mind from Nov. 6 to 15, 2026. From there, it will be on display in perpetuity
at the Turner Museum of Glass 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," Metcalfe 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."
While this specific glass will mainly have decorative applications, the scientific understanding gained will feed into new photonic materials and advanced glasses for radioactive waste management.
Provided by University of Sheffield
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