Ravenscroft
NAME:
Ravenscroft, George
ACHIEVEMENTS:
Developed flint glass
NICKNAME/ALIAS:
None
DATE AND PLACE OF BIRTH:
1618, England
DATE AND PLACE OF DEATH AND AGE AT DEATH:
1681, England. Aged 63
DISCIPLINE:
Glassmaker
FIELD:
Industry
LANGUAGE:
English
PARENTS:
Father: name?
Mother: name?
SIBLINGS:
?
SPOUSE:
?
CHILDREN:
?
EDUCATION:
?
MAJOR WORK:
None
LIFE AND TIMES:
Ravenscroft was the son of a prosperous merchant who traded with Venice. In the seventeenth century English merchants had become dissatisfied with the quality of imported glass, most of which came from Italy. The glassmakers of the island of Murano, in Venice, had dominated the trade in up-market glassware for centuries but their crystal glass was variable in quality.
After the restoration of the monarchy in 1660 and the founding of the Royal Society, there was a new wave of enthusiasm for experimental science in England. When the London Company of Glass Sellers was granted its charter of incorporation in 1664 they issued several patents for a new form of colorless crystal glass made with native raw materials, hoping to become independent of the importation of both materials and finished glass.
The work of <work related to> Percival* and others in replacing wood with coal as a fuel had already given England the advantage of hotter and more consistent temperatures in the glasshouses. Ravenscroft was interested in scientific matters and he had his own experimental glasshouse in London.
At some stage he was issued with a patent and in 1673 he was engaged by the Glass Sellers’ Company to research the making of glass in England. At first he replaced Venetian pebbles and Spanish “ barilla” :with transparent black English flints, ground to a fine white powder, and potash. This was not successful because after a short time the glass lost its transparency as networks of tiny cracks appeared.
However, Ravenscroft had produced such promising results that in 1674 the Glass Sellers financed his move to a more private glasshouse at Henley-on-Thames. The deterioration of the glass was caused by an excess of alkali and Ravenscroft solved this problem by replacing the potash with oxide of lead.
The calcined flint was replaced by sand and Ravenscroft eventually produced a clear crystal glass that was brilliant and lustrous. His process was declared a success and he was allowed to incorporate the seal of a raven’s head (part of the Ravenscroft family crest) on his finished pieces. Flint glass was heavier than the Italian ‘cristallo’, somewhat darker in color and highly refractive.
Ravenscroft died in 1681, a few days before the expiry of his patent. Because it was more durable, sales of flint glass gradually overtook the more delicate Venetian product and eventually new techniques of glassmaking in England began to replace methods developed by the Venetians.
Today, flint glass is used to make lenses and prisms and, because it absorbs most ultraviolet light and very little visible light, it is also used for telescope lenses.
ASSESSMENT: Ravenscroft invented a new type of crystal glass using English native raw materials which made England dominant in the production of colourless glass at the end of the seventeenth century.
EXTRA CONNECTIONS: None
ONELINER: George Ravenscroft, early English glassmaker
BIBLIOGRAPHY:
Vose, Ruth Hurst, Glass, William Collins Sons & Co. Ltd, London, 1980