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Cyflwynir y tudalen hwn yn Saesneg am nad yw wedi'i gyfieithu i'r Gymraeg hyd yn hyn.

Os hoffech i’r dudalen hon gael ei chyfieithu fel mater o flaenoriaeth, anfonwch gyfeiriad y dudalen hon at

The chameleon cup

05 Ionawr 2008

Lycurgus Cup - Green

Professor Ian Freestone of the School of History and Archaeology has re-examined the famous Roman colour-changing Lycurgus Cup.

The glass cup, which dates from the fourth century A.D., changes from green in reflected light to red when light is shone through it. Some years ago Professor Freestone conducted an investigation of the colour of the cup, using transmission electron microscopy to demonstrate that the colour effects were due to minute nanoparticles of a gold-silver alloy in the glass.

Lycurgus Cup - Red

The cup’s second unusual feature is its openwork decoration. The myth of King Lycurgus of Thrace is shown in openwork - a frieze attached to the main body of the glass by small shanks or bridges.

The current investigation, in association with a group from the British Museum, has focused on the production of the frieze. In contrast to a recent suggestion that it was moulded, the Cup appears to have been painstakingly cut from a blank, using drills and files charged with an abrasive slurry, probably of emery (corundum).

Professor Freestone said: "As is often the case, there was no mystery or magic involved, even in the production of a unique artefact such as this one. Traditional approaches, applied with a great deal of patience, care and skill, allowed the craftsman to produce objects which still impress today."