This bluish-green window pane is made up of several pieces. The edges are fairly smooth, so they perhaps form a complete pane. It is thicker (3mm) than most modern house window panes, and modern ones are normally of clear glass. This Roman example is made of the same utilitarian bluish-green glass as an urn with cremated bones, also in The British Museum.
Roman glass window panes were probably formed by casting in open moulds; this is one of the earliest surviving examples. It must have come from a house built before the eruption of Mt. Vesuvius in AD 79, which destroyed the cities of Pompeii and Herculaneum. Window panes of glass seem to have been unknown in earlier times.
The Roman author Pliny the Elder (AD 23/4-79), describes a theatre built in 58 BC: 'The lowest storey of the stage was of marble, and the middle one of glass, an extravagance unparalleled even in later times'. According to other literary references the use of glass in both public and private dwellings was a luxurious form of internal decoration throughout the Roman era, although available only to the wealthy. Glass window panes must have fallen into this category, since few survive, and even fewer are as complete as this example.