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.”

Maintaining traditional plain glass and glazing, published on 1 November 2007 by Historic Scotland, states: ‘Crown glass was made by blowing and then spinning molten glass into a large thin disc known as a ‘table’ which was then cut into smaller panes. The glass is slightly curved and distinctive semi-circular lines called the ‘ream’ can often be seen in the glass. Crown glass is thinner than cylinder glass, but is also brighter and shinier as it never came in contact with a hard surface while molten. The seed lies in concentric circles, and panes often have a ‘bellied’ appearance when used in windows. Crown glass became increasingly popular from the middle of the 18th Century.’

NB 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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