The breakthrough centres on the famous Lycurgus Cup, a Roman glass vessel held at the British Museum. Its extraordinary optical properties have fascinated researchers for years, and the latest achievement offers fresh insight into the technique used to produce its distinctive colour-changing effect.
According to the University of Sheffield's official website, the research team successfully reproduced the effect using a repeatable glass recipe. The original artefact is made from a special type of glass known as dichroic glass, which displays different colours depending on how light interacts with it.
The achievement follows extensive experiments by Dr Lisa Hollands, a technician in the university's School of Chemical, Materials and Biological Engineering, working with Professor Caroline Jackson, an expert in Roman glass.
The British Museum dates the Lycurgus Cup to the fourth century AD. Its collection record identifies it as a Late Roman drinking cup made of glass, with silver-gilt fittings around its rim and base. The vessel's unusual colour-changing properties are linked to tiny quantities of gold and silver incorporated into the glass during its manufacture.
According to the University of Sheffield, these metals formed nanoparticles, particles thousands of times smaller than a grain of sand, which interact with light in unusual ways. When light reflects off the cup, the glass appears jade green. When light passes through it, the glass takes on a ruby-red appearance.
The effect depends on the position of the light source and the way the glass absorbs and scatters different wavelengths of light. The nanoparticles are smaller than the wavelengths of visible light, and their size and shape influence the colours observed.
Producing the distinctive effect therefore requires precise control over the composition and formation of these particles.
The Lycurgus Cup is particularly notable because, according to the University of Sheffield, it is the only surviving example of a Roman glass cage cup known to display this exceptional colour-changing behaviour.
Cage cups are elaborate vessels in which decorative glasswork is cut away from the main body, leaving figures and patterns connected by narrow bridges.
Years of Experiments to Recreate an Ancient Technique
To reproduce the effect, the research team examined existing knowledge of Roman glassmaking and developed a base glass using modern materials intended to mimic those available to ancient craftsmen.
The greater challenge was incorporating small quantities of gold and silver into the glass in the correct form.
The researchers tested different furnaces, starting materials and oxygen levels. Their experiments even included adding sugar to the mixture.
After extensive trials, Hollands developed a recipe that produced glass appearing opaque green in reflected light and red when illuminated from behind.
The successful reproduction provides a repeatable method for creating the unusual optical effect, bringing researchers closer to understanding the glassmaking technique used by Roman craftsmen.
Modern Sculpture Inspired by the Ancient Cup
Following the exhibition of the initial glass at LightFest, the researchers commissioned glass artist Elliot Walker to create a contemporary sculpture using Hollands' recipe.
Walker won season two of Netflix's Blown Away.
The sculpture draws inspiration from the story depicted on the original cup and the form of the ancient Farnese Atlas sculpture. Walker explained that the design needed a blown-glass element to demonstrate the colour-changing effect clearly.
The new work is scheduled to be unveiled at Sheffield's Millennium Gallery during the University's Festival of the Mind, running from November 6 to 15, 2026.
The university says the sculpture will subsequently go on permanent display at its Turner Museum of Glass.
Research Could Have Applications Beyond Art
Although the recreated glass has immediate decorative potential, the research also has wider scientific relevance.
According to the University of Sheffield, the project forms part of work exploring materials that use light for applications in areas such as solar energy, quantum technologies and healthcare diagnostics.
The knowledge gained may also contribute to the development of advanced glasses used to immobilise radioactive waste.
The findings therefore extend beyond reproducing an ancient artefact, offering insights into how carefully controlled materials can interact with light for potential technological applications.
The Lycurgus Cup itself remains at the British Museum. Its collection record describes the vessel as a fourth-century Roman drinking cup decorated with scenes from the story of Lycurgus, the mythical king of Thrace.
In the myth depicted on the cup, Lycurgus attacks Dionysus and his followers. Ambrosia, one of the god's companions, is transformed into a vine that coils around and traps the king.
The vessel combines this elaborate mythological decoration with an optical effect that continues to attract scientific attention.
By recreating its colour-changing glass through a repeatable recipe, the University of Sheffield team has advanced understanding of how a technique developed by ancient Roman glassmakers can be reproduced using modern materials and scientific methods, while also opening possibilities for further research into materials that interact with light.
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