Crown glass
Historic England 2020 Stained Glass Windows: Managing Environmental Deterioration, Swindon, published by Historic England in 2020 defines crown glass, or spun glass as a: “Method of producing sheet glass by hand. A bubble of molten glass is transferred onto a solid metal ‘punty rod’, or ‘pontil rod’, which can be spun between the hands of the glass blower. The blowing pipe is then cut away, and the molten glass spun using the punty rod until it suddenly opens out into a disc, or ‘table’. The earliest known crown glass in England dates from the 1440s; it was widely used for windows until the mid-19th century, when taxation by weight ceased and cylinder glass became cheaper.”
Archaeological Evidence for Glassworking, Guidelines for Recovering, Analysing and Interpreting Evidence, published by Historic England in 2018, defines a pontil scar as: 'The circular protrusion of glass left on a glass object after removal of the pontil iron, although it was ground away on finer vessels.'
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