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The Portland Vase, dated to the 1st century and on display at the British Museum, has long been considered the finest surviving example of the emerging art of Roman glass blowing. Research led by Richard Whitely of the Australian National University in Canberra, however, reveals the vase has been wrongly catalogued for centuries: it was actually made by an older method.
By making virtual slices through the vase using computed tomography (CT) scans, Whitely found tiny trapped bubbles in the glass. “You just would not get a bubble that size and flat-shaped from blowing,” he says. The bubbles are instead indicative of a process now known as ‘pate de verre’, a still-popular technique in 1st century Rome where a paste of powdered glass is pressed into a mould then fired.