Ravenscroft, George

SUBJECT AREA: Chemical technology, Photography, film and optics

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b. 1632 Alconbury, Huntingdonshire, England

d. 7 June 1683 Barnet, Hertfordshire, England

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English inventor of lead-crystal glass.

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George's father James was a successful lawyer and merchant, engaging in overseas trade.

A devout but necessarily circumspect Catholic, James sent his sons to the English College at Douai, now in northern France. Leaving there in 1651, George began to learn his father's business and spent some fifteen years in Venice. He took an increasingly important part in it, doubtless dealing in Venice's leading products of lace and glass. By 1666 he was back in England and, perhaps because the supply of Venetian glass was beginning to decline, he started to manufacture glass himself. In 1673 he set up a glassworks in the Savoy in London and succeeded so well that in the following year he petitioned the King for the grant of a patent to make glassware. This was granted on 16 May 1674, stimulating the Glass Sellers' Company to enter into an agreement with Ravenscroft to buy the glassware he produced. Later in 1674 the company allowed Ravenscroft to establish a second glasshouse at Henley-onThames. At first his ware was beset with "crizzling", i.e. numerous fine surface cracks. The Glass Sellers probably urged Ravenscroft to cure this defect, and this he achieved in 1675 by replacing crushed flint with increasing amounts of lead oxide, rising finally to a content of 30 per cent. He thereby obtained a relatively soft, heavy glass with high refractive index and dispersive power. This made it amenable to deep cutting, to produce the brilliant prismatic effects of cut glass. At about the same time, the Duke of Buckingham, a considerable promoter of the glass industry, agreed that Ravenscroft should manage his works at Vauxhall for the making of plate glass for mirrors. Ravenscroft terminated his agreement with the Glass Sellers in 1678, the date of the last evidence of his activities as a maker of crystal glass, and the patent expired in 1681. His new glass had immediately rivalled the best Venetian crystal glass and has been a valued product ever since.

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Further Reading

R.F.Moody, 1988, The life of George Ravenscroft', Glass Technology 29 (1):198–210;

Glass Technology 30(5):191–2 (additional notes on his life).

LRD