Archaeological evidence for glass making during the Roman period is scarce, but by drawing comparisons with the later Islamic and Byzantine periods, it is clear that glass making was a significant industry. By the end of the Roman period glass was being produced in large quantities contained in tanks situated inside highly specialised furnaces, as the 8-tonne glass slab recovered from Bet She'arim illustrates.[1] These workshops could produce many tonnes of raw glass in a single furnace firing, and although this firing might have taken weeks, a single primary workshop could potentially supply multiple secondary glass working sites. It is therefore thought that raw glass production was centred around a relatively small number of workshops,[11] where glass was produced on a large scale and then broken into chunks.[12] There is only limited evidence for local glass making, and only in context of window glass.[3] The development of this large-scale industry is not fully understood, but Pliny's Natural History (36, 194), in addition to evidence for the first use of molten glass in the mid-1st century AD,[4] indicates that furnace technologies experienced marked development during the early-to-mid-1st century AD, in tandem with the expansion of glass production.