Cylinder glass

Historic England 2020 Stained Glass Windows: Managing Environmental Deterioration, Swindon, Historic England, published in 2020 defines broad glass, or cylinder glass as: “The principal method of making sheet glass by hand, developed in the early Middle Ages, and still in use. The glass maker swings a bubble of molten glass back and forth whilst blowing, producing an elongated balloon. The end of the balloon is opened out using a hot iron tool, and it is then cut from the blowing rod to produce a cylinder of glass. This is scored down its length and returned to a kiln, where the heat causes the cylinder to open out along the scored line and flatten into a sheet.”

Maintaining traditional plain glass and glazing, published on 1 November 2007 by Historic Scotland, states: ‘Cylinder glass (also known as ‘broad, ‘sheet’, or ‘muff’ glass) was made by blowing a cylinder of molten glass. This cylinder was cut along its side and flattened out in a furnace, giving the glass a slightly rippled surface. It can also be recognised by the pattern of the ‘seed’ which consists of elongated air bubbles that lie in straight parallel lines within the glass. Popular until the first half of the 18th Century.’

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