George Ravenscroft
Encyclopedia
George Ravenscroft was an English businessman in the import/export and glass
making trades. He is primarily known for his work in developing clear lead crystal glass (also known as flint glass
) in England
.
, England, in April 1633. From 1643 to 1651 Ravenscroft attended the English College in Douai
, France
to train for the priesthood, but he dropped out before finishing his training and returned to London
by 1666.
After settling in London and establishing a successful import/export business that made him wealthy, Ravenscroft married Hellen Appleby, from Yorkshire
, England, in 1670 or 1671 and had three children with her. Ravenscroft died on 7 June 1683 after suffering from “a palsy
” and was buried in the Ravenscroft vault in the Church of St.John the Baptist in Chipping Barnet, North London
, England. Today in Chipping Barnet a school, a park, a garden, and a road are called Ravenscroft, suggesting the importance of the Ravenscroft family in the area at one time.
, Italy
for at least some of this time working as a merchant and possibly learning glassmaking techniques that he would later bring back to England. At some point he established a successful import/export business in Venice with two of his brothers, Francis and James.
, glass
, and lace
. There are differing accounts of Ravenscroft’s role in the invention and subsequent development of lead crystal glass. This much is generally accepted to be true: During the years Ravenscroft lived in Venice (sometime between 1651 and 1666) he was involved in the glass trade, not as a craftsman but as a merchant, so he knew and associated with glassmakers in Italy. By the time Ravenscroft moved back to England several glassmakers there had already started manufacturing glassware that attempted to mimic Italian cristallo
, and Ravenscroft decided to start his own glass-making business while still running his import/export business.
It is likely that Ravenscroft was the director and financier of his glassworks but not actively involved in the physical process of glass-making, a role likely to have been performed by one or more craftsmen in his employ, such as Italians Signor da Costa or Vincenzo Pompeio, or his English assistant Hawley Bishopp, who set up his own glassworks, in the Savoy area of London, after Ravenscroft’s death. Ravenscroft’s glassworks produced mainly drinking glasses but also made some bowls and posset pots
.
At this point the circumstances concerning Ravenscroft’s role in lead crystal manufacture becomes less clear. This is partly because records from the mid-17th century are incomplete, but is also largely because Ravenscroft was secretive about his ingredients and processes. There is proof that he was helped by Sir Robert Plot FRS, who suggested using flints from Oxfordshire river beds in place of dark grey London flints t the very expensive white flints from the river bed of the River Po in Italy as used in Murano. It is now believed that Dr Plot requested a sample of his powder which was described as being "fine and white". If he added lead oxide ( in a red lead powder form), the powder would appear pale pink, so he may have deliberately have misled Dr Plot and his assistant sent to visit in Henley on Thames. He was probably careful to prevent competitors from copying him and also wished to agree a deal with the Worshipful Company of Glass Sellers of London Glass Sellers’ Company, to which he gave exclusive rights to buy his creations at pre-determined prices in return for a grant to finance his Henley-on-Thames workshop, with two teams of glass blowers.
There is some debate over how, when, and why Ravenscroft was inspired to use lead in the production of glass. Some believe that he accidentally discovered that adding lead oxide
to the glass mixture lent the final product special qualities, while others believe that he learned the technique in Venice. The use of lead in glass was known in Italy as proved by 10% lead being discovered in the white cameo layer of The Portland Vase, a famous Roman artefact in the British museum. Whatever the origin of the idea, Ravenscroft believed that he had a unique product to offer the English market, so he applied to King Charles II for a patent
in 1674 to establish his right to be sole manufacturer of lead crystal glass in England. He produced lead crystal glass for a period of only five years, dissolving his manufacturing business in 1679. His patent expired in 1681.
Ravenscroft’s glass works were set up in two locations, the primary facility being established in Savoy, London in 1673 and a secondary, temporary facility set up between 1674 and 1675 in Henley-on-Thames
.
Early Ravenscroft glass (1674–1676) typically suffered from crizzling (gradual, unstoppable deterioration characterized by numerous cracks, making the glass look cloudy), within 1 to 2 years, because of impurities in the glass-making mixture - excessive alkaline salts or insufficient amounts of lime, which acts as a stabilizer, have been suggested as possible causes. No early pieces are known to still exist.
The "crizzling" damaged the reputation of the company, and Ravenscroft and his team worked to fix the problem. Ravenscroft announced in 1676 that the "crizzling" problem had been resolved and that the new, improved glass vessels would bear a raven
’s head seal to distinguish them from earlier, faulty pieces. A small number, ( less than twenty) of glass vessels bearing the raven’s head seal exist today, some of which have crizzled and some of which have not.
More pieces created by Ravenscroft may exist, but in the absence of the raven’s head seal, which he stopped using in about 1677, or any descriptions or drawings of his designs, it is difficult to positively attribute particular pieces to him. Some pieces thought to strongly resemble Ravenscroft’s work bear an “S” seal; some have suggested that the “S” stands for “Savoy,” Ravenscroft’s main production facility, while others believe that the “S” stands for “Southwark
,” indicating the South London glass works of John Bowles and William Lillington.There may be around forty glass items made by Ravenscroft using his new lead recipe.
The addition of lead oxide
to the raw ingredients of glass resulted in a melted mixture that had a lower viscosity than ordinary glass, which had the advantage of being less likely to contain air bubbles. This made it easier to blow giving it a "working time" of about two minutes without re-heating, and made it particularly suitable for blowing into moulds. Lead glass has a higher refractive index
, making its appearance sparkling, bright, and brilliant in light. It “rings” when struck.
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
making trades. He is primarily known for his work in developing clear lead crystal glass (also known as flint glass
Flint glass
Flint glass is optical glass that has relatively high refractive index and low Abbe number. Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less. The currently known flint glasses have refractive indices ranging between 1.45 and 2.00...
) in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
.
Personal life
Little is known about Ravenscroft’s personal life, character, or appearance, though his father described him in his will as a responsible family man and an astute businessman. He was born in 1632, the second of five sons of Roman Catholic parents who hid their true faith and lived outwardly as Anglicans, and he was baptized in Alconbury WestonAlconbury Weston
Alconbury Weston - in Huntingdonshire , England - is a village near Alconbury north-west of Huntingdon, lying just outside the Fens, has just a few hills, but a significant change to the flat of the Fens....
, England, in April 1633. From 1643 to 1651 Ravenscroft attended the English College in Douai
English College, Douai
The English College, Douai was a Catholic seminary associated with the University of Douai . It was established in about 1561, and was suppressed in 1793...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
to train for the priesthood, but he dropped out before finishing his training and returned to London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
by 1666.
After settling in London and establishing a successful import/export business that made him wealthy, Ravenscroft married Hellen Appleby, from Yorkshire
Yorkshire
Yorkshire is a historic county of northern England and the largest in the United Kingdom. Because of its great size in comparison to other English counties, functions have been increasingly undertaken over time by its subdivisions, which have also been subject to periodic reform...
, England, in 1670 or 1671 and had three children with her. Ravenscroft died on 7 June 1683 after suffering from “a palsy
Palsy
In medicine, palsy is the paralysis of a body part, often accompanied by loss of sensation and by uncontrolled body movements, such as shaking. Medical conditions involving palsy include cerebral palsy , brachial palsy , and Bell's palsy ....
” and was buried in the Ravenscroft vault in the Church of St.John the Baptist in Chipping Barnet, North London
North London
North London is the northern part of London, England. It is an imprecise description and the area it covers is defined differently for a range of purposes. Common to these definitions is that it includes districts located north of the River Thames and is used in comparison with South...
, England. Today in Chipping Barnet a school, a park, a garden, and a road are called Ravenscroft, suggesting the importance of the Ravenscroft family in the area at one time.
Early career (1651–1666)
Ravenscroft’s whereabouts and activities between 1651 and 1666 are unclear, though it is certain that he lived in VeniceVenice
Venice is a city in northern Italy which is renowned for the beauty of its setting, its architecture and its artworks. It is the capital of the Veneto region...
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
for at least some of this time working as a merchant and possibly learning glassmaking techniques that he would later bring back to England. At some point he established a successful import/export business in Venice with two of his brothers, Francis and James.
Background
Ravenscroft moved to London by 1666 and continued working in the import/export business, trading goods such as currantsRibes
Ribes is a genus of about 150 species of flowering plants native throughout the temperate regions of the Northern Hemisphere. It is usually treated as the only genus in the family Grossulariaceae. Seven subgenera are recognized....
, glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
, and lace
Lace
Lace is an openwork fabric, patterned with open holes in the work, made by machine or by hand. The holes can be formed via removal of threads or cloth from a previously woven fabric, but more often open spaces are created as part of the lace fabric. Lace-making is an ancient craft. True lace was...
. There are differing accounts of Ravenscroft’s role in the invention and subsequent development of lead crystal glass. This much is generally accepted to be true: During the years Ravenscroft lived in Venice (sometime between 1651 and 1666) he was involved in the glass trade, not as a craftsman but as a merchant, so he knew and associated with glassmakers in Italy. By the time Ravenscroft moved back to England several glassmakers there had already started manufacturing glassware that attempted to mimic Italian cristallo
Cristallo
Cristallo is a glass which is totally clear , without the slight yellow or greenish color originating from iron oxide impurities. This effect is achieved through small additions of manganese oxide...
, and Ravenscroft decided to start his own glass-making business while still running his import/export business.
It is likely that Ravenscroft was the director and financier of his glassworks but not actively involved in the physical process of glass-making, a role likely to have been performed by one or more craftsmen in his employ, such as Italians Signor da Costa or Vincenzo Pompeio, or his English assistant Hawley Bishopp, who set up his own glassworks, in the Savoy area of London, after Ravenscroft’s death. Ravenscroft’s glassworks produced mainly drinking glasses but also made some bowls and posset pots
Posset
A posset was a British hot drink of milk curdled with wine or ale, often spiced, which was popular from medieval times to the 19th century...
.
At this point the circumstances concerning Ravenscroft’s role in lead crystal manufacture becomes less clear. This is partly because records from the mid-17th century are incomplete, but is also largely because Ravenscroft was secretive about his ingredients and processes. There is proof that he was helped by Sir Robert Plot FRS, who suggested using flints from Oxfordshire river beds in place of dark grey London flints t the very expensive white flints from the river bed of the River Po in Italy as used in Murano. It is now believed that Dr Plot requested a sample of his powder which was described as being "fine and white". If he added lead oxide ( in a red lead powder form), the powder would appear pale pink, so he may have deliberately have misled Dr Plot and his assistant sent to visit in Henley on Thames. He was probably careful to prevent competitors from copying him and also wished to agree a deal with the Worshipful Company of Glass Sellers of London Glass Sellers’ Company, to which he gave exclusive rights to buy his creations at pre-determined prices in return for a grant to finance his Henley-on-Thames workshop, with two teams of glass blowers.
There is some debate over how, when, and why Ravenscroft was inspired to use lead in the production of glass. Some believe that he accidentally discovered that adding lead oxide
Lead oxide
Lead oxide may refer to:* Lead oxide, PbO, litharge, massicot* Lead oxide, Pb3O4, minium, red lead* Lead dioxide , PbO2Less common lead oxides are:* Lead oxide, Pb2O3, lead sesquioxide...
to the glass mixture lent the final product special qualities, while others believe that he learned the technique in Venice. The use of lead in glass was known in Italy as proved by 10% lead being discovered in the white cameo layer of The Portland Vase, a famous Roman artefact in the British museum. Whatever the origin of the idea, Ravenscroft believed that he had a unique product to offer the English market, so he applied to King Charles II for a patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
in 1674 to establish his right to be sole manufacturer of lead crystal glass in England. He produced lead crystal glass for a period of only five years, dissolving his manufacturing business in 1679. His patent expired in 1681.
Ravenscroft’s Lead Crystal Glass
Henley-on-Thames
Henley-on-Thames is a town and civil parish on the River Thames in South Oxfordshire, England, about 10 miles downstream and north-east from Reading, 10 miles upstream and west from Maidenhead...
.
Early Ravenscroft glass (1674–1676) typically suffered from crizzling (gradual, unstoppable deterioration characterized by numerous cracks, making the glass look cloudy), within 1 to 2 years, because of impurities in the glass-making mixture - excessive alkaline salts or insufficient amounts of lime, which acts as a stabilizer, have been suggested as possible causes. No early pieces are known to still exist.
The "crizzling" damaged the reputation of the company, and Ravenscroft and his team worked to fix the problem. Ravenscroft announced in 1676 that the "crizzling" problem had been resolved and that the new, improved glass vessels would bear a raven
Raven
Raven is the common name given to several larger-bodied members of the genus Corvus—but in Europe and North America the Common Raven is normally implied...
’s head seal to distinguish them from earlier, faulty pieces. A small number, ( less than twenty) of glass vessels bearing the raven’s head seal exist today, some of which have crizzled and some of which have not.
More pieces created by Ravenscroft may exist, but in the absence of the raven’s head seal, which he stopped using in about 1677, or any descriptions or drawings of his designs, it is difficult to positively attribute particular pieces to him. Some pieces thought to strongly resemble Ravenscroft’s work bear an “S” seal; some have suggested that the “S” stands for “Savoy,” Ravenscroft’s main production facility, while others believe that the “S” stands for “Southwark
Southwark
Southwark is a district of south London, England, and the administrative headquarters of the London Borough of Southwark. Situated east of Charing Cross, it forms one of the oldest parts of London and fronts the River Thames to the north...
,” indicating the South London glass works of John Bowles and William Lillington.There may be around forty glass items made by Ravenscroft using his new lead recipe.
The addition of lead oxide
Lead oxide
Lead oxide may refer to:* Lead oxide, PbO, litharge, massicot* Lead oxide, Pb3O4, minium, red lead* Lead dioxide , PbO2Less common lead oxides are:* Lead oxide, Pb2O3, lead sesquioxide...
to the raw ingredients of glass resulted in a melted mixture that had a lower viscosity than ordinary glass, which had the advantage of being less likely to contain air bubbles. This made it easier to blow giving it a "working time" of about two minutes without re-heating, and made it particularly suitable for blowing into moulds. Lead glass has a higher refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
, making its appearance sparkling, bright, and brilliant in light. It “rings” when struck.
Legacy
It is not known why Ravenscroft decided to sever his ties with the London Glass Sellers’ Company and leave the glass-making business in 1679, ( his strong Roman Catholic beliefs might have made him unpopular), but his style of lead crystal glass became fashionable in England and within 20 years of his patent some 100 glass makers in England were producing lead crystal glass. Ravenscroft did not “invent” lead crystal glass, as others had already discovered the advantages of adding lead oxide to glass, but he did improve the process. More than a dozen of Ravenscroft’s pieces are known to exist (see table below), and the “robust simplicity” of his designs is still admired.| Description | Date of Manufacture | Location | Condition |
|---|---|---|---|
| Bowl | 1676–1677 | Victoria & Albert Museum, London, UK | crizzled |
| Bowl with stand | 1676–1677 | Fitzwilliam Museum Fitzwilliam Museum The Fitzwilliam Museum is the art and antiquities museum of the University of Cambridge, located on Trumpington Street opposite Fitzwilliam Street in central Cambridge, England. It receives around 300,000 visitors annually. Admission is free.... , Cambridge Cambridge The city of Cambridge is a university town and the administrative centre of the county of Cambridgeshire, England. It lies in East Anglia about north of London. Cambridge is at the heart of the high-technology centre known as Silicon Fen – a play on Silicon Valley and the fens surrounding the... , UK |
crizzled |
| Roemer Rummer Rummers, Römers or Roemers, were large drinking-glasses studded with prunts to ensure a safe grip, popular in the Rhineland and the Netherlands from the 15th through the 17th century. They lacked the flared bowl of the Berkemeyer and had much thinner walls. The hollow base was built up by coiling... |
1676–1677 | Victoria & Albert Museum, London, UK | crizzled |
| Roemer | 1676–1677 | Corning Museum of Glass Corning Museum of Glass The Corning Museum of Glass, in Corning, New York, explores every facet of glass, including art, history, culture, science and technology, craft, and design.... , Corning, NY Corning (city), New York Corning is a city in Steuben County, New York, United States, on the Chemung River. The population was 10,842 at the 2000 census. It is named for Erastus Corning, an Albany financier and railroad executive who was an investor in the company that developed the community.- Overview :The city of... , USA |
crizzled |
| Roemer | 1677–1678 | Muzeum Narodowe, Warsaw Warsaw Warsaw is the capital and largest city of Poland. It is located on the Vistula River, roughly from the Baltic Sea and from the Carpathian Mountains. Its population in 2010 was estimated at 1,716,855 residents with a greater metropolitan area of 2,631,902 residents, making Warsaw the 10th most... , Poland Poland Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north... |
not crizzled |
| Bottle | 1676–1677 | British Museum, London, UK | slightly crizzled |
| Jug | 1676–1677 | Cecil Higgins Museum Bedford Museum & Art Gallery Cecil Higgins Art Gallery & Bedford Museum is the principal art gallery and museum in Bedford, Bedfordshire, England, run by Bedford Borough Council and the Trustees of the Cecil Higgins Collection.- Overview :... , Bedford Bedford Bedford is the county town of Bedfordshire, in the East of England. It is a large town and the administrative centre for the wider Borough of Bedford. According to the former Bedfordshire County Council's estimates, the town had a population of 79,190 in mid 2005, with 19,720 in the adjacent town... , UK |
crizzled |
| Tankard | 1676–1677 | Victoria & Albert Museum, London, UK | crizzled |
| Posset Posset A posset was a British hot drink of milk curdled with wine or ale, often spiced, which was popular from medieval times to the 19th century... pot |
Unknown | Toledo Museum of Art Toledo Museum of Art The Toledo Museum of Art is an internationally known art museum located in the Old West End neighborhood of Toledo, Ohio, United States. The museum was founded by Toledo glassmaker Edward Drummond Libbey in 1901, and moved to its present location, a Greek revival building designed by Edward B.... , Toledo, OH, USA |
not crizzled |
| Posset pot | 1677–1678 | Fitzwilliam Museum, Cambridge, UK | not known |
| data in table above taken from and |