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Cloisonné enamel plaque, Byzantine Empire, ca. 1100

The Royal Gold Cup with basse-taille enamels; weight 1.935 kg, British Museum. Saint Agnes appears to her friends in a vision.

St. Gregory the Great in painted Limoges enamel on a copper plaque, by Jacques I Laudin

Vitreous enamel, also porcelain enamel in U.S. English, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C (1,382 and 1,562 °F). The powder melts, flows, and then hardens to a smooth, durable vitreous coating on metal, and also glass or ceramics, although the use of the term "enamel" is often restricted to work on metal, which is all that this article covers; enameled glass is also called "painted". The fired enameled ware is a fully laminated composite of glass and metal. The word enamel comes from the High German word smelzan (to smelt) via the Old French esmail.^[1] Used as a noun, "an enamel" is a usually small decorative object, coated with enamel coating. Enameling is an old and widely-adopted technology, for most of its history mainly used in jewelry and decorative art, but since the 19th century applied also to industrial materials and everyday consumer objects, especially cooking vessels. "Enamelled" and "enamelling" are the preferred spellings in British English, while "enameled" and "enameling" are preferred in American English.

History[link]

The ancient Egyptians applied enamels to pottery and stone objects, and sometimes jewelry, though the last less often than other ancient Middle Eastern cultures. The ancient Greeks, Celts, Georgians, and Chinese also used enamel on metal objects.^[2]

Enamel was also sometimes used to decorate glass vessels during the Roman period, and there is evidence of this as early as the late Republican and early Imperial periods in the Levantine, Egypt, Britain and the Black Sea.^[3] Enamel powder could be produced in two ways; either through the powdering of colored glass, or the mixing of colorless glass powder with pigments such as a metallic oxide.^[4] Designs were either painted freehand or over the top of outline incisions, and the technique probably originated in metalworking.^[3] Once painted, enameled glass vessels needed to be fired at a temperature high enough to melt the applied powder, but low enough that the fabric of the vessel itself was not melted. Production is thought to have come to a peak in the Claudian period and persisted for some three hundred years,^[3] though archaeological evidence for this technique is limited to some forty vessels or vessel fragments.^[3]

Enamel was at its most important in European art history in the Middle Ages, beginning with the Late Romans and then the Byzantines who began to use cloisonné enamel in imitation of cloisonné inlays of precious stones. This style was widely adopted by the "barbarian" peoples of Migration Period northern Europe. The Byzantines then began to use cloisonné more freely to create images, which was also copied in Western Europe. The champlevé technique was considerably easier, and very widely practiced in the Romanesque period. In Gothic art the finest work is in basse-taille and ronde-bosse techniques, but cheaper champlevé works continued to be produced in large numbers for a wider market.

From Byzantium or the Islamic world the cloisonné technique reached China in the 13-14th centuries; the first written reference is in a book of 1388, where it is called "Dashi ('Muslim') ware".^[5] No Chinese pieces clearly from the 14th century are known, the earliest datable pieces being from the reign of the Xuande Emperor (1425–35), which however show a full use of Chinese styles suggesting considerable experience in the technique. It remained very popular in China until the 19th century, and is still produced today. The most elaborate and highly-valued Chinese pieces are from the early Ming Dynasty, especially the reigns of the Xuande Emperor and Jingtai Emperor (1450–57), although 19th century or modern pieces are far more common.^[6] The Japanese also produced large quantities from the mid-19th century, of very high technical quality.^[7]

From more recent history, the bright, jewel-like colors have made enamel a favored choice for designers of jewelry and bibelots, such as the fantastic eggs of Peter Carl Fabergé, enameled copper boxes of Battersea enamellers, and artists such as George Stubbs and other painters of portrait miniatures. Enameling was a favorite technique of the Art Nouveau jewelers. A resurgence in enamel based art took place near the end of the 20th Century in the Soviet Union led by artists like Alexei Maximov and Leonid Efros.

Enamel was first applied commercially to sheet iron and steel in Austria and Germany in about 1850.^[8] Industrialization increased as the purity of raw materials increased and costs decreased. The wet application process started with the discovery of the use of clay to suspend frit in water. Developments that followed during the twentieth century include enameling-grade steel, cleaned-only surface preparation, automation, and ongoing improvements in efficiency, performance, and quality.^[9]

Properties[link]

Enamel may be transparent or opaque when fired; vitreous enamel can be applied to most metals. The great majority of modern industrial enamel is applied to steel in which the carbon is controlled to prevent reactions at the firing temperatures. Enamel can also be applied to copper, aluminium,^[10] stainless steel,^[11] cast iron^[12] or hot rolled steel, as well as gold and silver.

Vitreous enamel has many excellent properties: it is smooth, hard, chemically resistant, durable, scratch resistant (5-6 on the Mohs scale), long-lasting color fastness, easy-to-clean, and cannot burn. Enamel is glass, not paint, so it does not fade with UV light.^[13] Its disadvantages are its tendency to crack or shatter when the substrate is stressed or bent, but modern enamels are chip and impact resistant because of good thickness control and thermal expansions well-matched to the metal. Its durability has found it many functional applications: early 20th century and some modern advertising signs, interior oven walls, cooking pots, exterior walls of kitchen appliances, cast iron bathtubs, farm storage silos, and processing equipment such as chemical reactors and pharmaceutical chemical process tanks. Commercial structures such as filling stations, bus stations and even Lustron Houses had walls, ceilings and structural elements made of enameled steel. One of the most widespread use of enamel is in the production of quality chalk-boards and marker-boards (typically called 'blackboards' or 'whiteboards') where the wear and chemical resistance properties of the enamel ensure that 'ghosting' or unerasable marks will not occur from normal use as they will with cheaper polymer boards. And, since standard enameling steel is magnetically attractive, they may also be used as magnet boards. Some new developments in the last ten years include enamel/non-stick hybrid coatings, sol-gel functional top-coats for enamels, enamels with a metallic appearance, and new easy-to-clean technologies.^[14]

The key ingredient of vitreous enamel is a highly friable form of glass called frit. Frit is typically an alkali borosilicate chemistry with a thermal expansion and glass temperature suitable for coating steel. Raw materials are smelted together between 2,100 and 2,650 °F (1,149 and 1,454 °C) into a liquid glass that is directed out of the furnace and thermal shocked with either water or steel rollers into frit.^[15]

Color in enamel is obtained by the addition of various minerals, often metal oxides cobalt, praseodymium, iron, or neodymium. The last creates delicate shades ranging from pure violet through wine-red and warm gray. Enamel can be either transparent, opaque or opalescent (translucent), which is a variety that gains a milky opacity the longer it is fired. Different enamel colors cannot be mixed to make a new color, in the manner of paint. This produces tiny specks of both colors; although the eye can be tricked by grinding colors together to an extremely fine, flour-like, powder.

There are three main types of frit. First, ground coats contain smelted-in transition metal oxides such as cobalt, nickel, copper, manganese, and iron that facilitate adhesion to steel. Second, clear and semi-opaque frits contain little coloring material for producing colors. Finally, titanium white cover coat frits are supersaturated with titanium dioxide which creates a bright white color during firing.

After smelting, the frit needs to be processed into one of the three main forms of enamel coating material. First, wet process enamel slip (or slurry) is a high solids loading product of grinding the frit with clay and other viscosity-controlling electrolytes. Second, ready-to-use (RTU) is a cake-mix form of the wet process slurry that is ground dry and can be reconstituted by mixing with water at high shear. Finally, electrostatic powder that can be applied as a powder coating is produced by milling frit with a trace level of proprietary additives. The frit may also be ground as a powder or into a paste for jewelry or silk-screening application.

• 

  View into a glass lined chemical reactor

• 

  Turb-mixer in a glass lined chemical reactor

Techniques of artistic enameling[link]

Limoges? grisaille Stations of the Cross, Notre-Dame-des-Champs, Avranches

Old German enamel street sign

• Basse-taille, from the French word meaning "low-cut". The surface of the metal is decorated with a low relief design which can be seen through translucent and transparent enamels. The 14th century Royal Gold Cup is an outstanding example.^[16]
• Champlevé, French for "raised field", where the surface is carved out to form pits in which enamel is fired, leaving the original metal exposed; the Romanesque Stavelot Triptych is an example.^[17]
• Cloisonné, French for "cell", where thin wires are applied to form raised barriers, which contain different areas of (subsequently applied) enamel. Widely practiced in Europe, the Middle East and East Asia.^[18]
• Grisaille, French term meaning "in grey", where a dark, often blue or black background is applied, then a palescent (translucent) enamel is painted on top, building up designs in a monochrome gradient, paler as the thickness of the layer of light color increases.
• Limoges enamel, made at Limoges, France, the most famous European center of vitreous enamel production. Limoges became famous for champlevé enamels from the 12th century onwards, producing on a large scale, and then from the 15th century retained its lead by switching to painted enamel on flat metal plaques.
• Painted enamel, a design in enamel is painted onto a smooth metal surface. Grisaille and later Limoges enamel are types of painted enamel.^[19] Most traditional painting on glass, and some on ceramics, uses what is technically enamel, but is often described by terms such as "painted in enamels", reserving "painted enamel" and "enamel" as a term for the whole object for works with a metal base.^[20]
• Plique-à-jour, French for "open to daylight" where the enamel is applied in cells, similar to cloisonné, but with no backing, so light can shine through the transparent or translucent enamel. It has a stained-glass like appearance; the Mérode Cup is the surviving medieval example.^[21]
• Ronde bosse, French for "in the round", also known as "encrusted enamel". A 3D type of enameling where a sculptural form or wire framework is completely or partly enameled, as in the 15th century Holy Thorn Reliquary.^[22]
• Stenciling, where a stencil is placed over the work and the powdered enamel is sifted over the top. The stencil is removed before firing, the enamel staying in a pattern, slightly raised.
• Sgrafitto, where an unfired layer of enamel is applied over a previously fired layer of enamel of a contrasting color, and then partly removed with a tool to create the design.
• Serigraph, where a silkscreen is used with 60-70in grade mesh.
• Counter enameling, not strictly a technique, but a necessary step in many techniques, is to apply enamel to the back of a piece as well - sandwiching the metal - to create less tension on the glass so it does not crack.

Industrial Enamel Application[link]

On sheet steel, a ground coat layer is put on first to create adhesion. The only surface preparation required for modern ground coats is a simply degreasing of the steel with a mildly alkaline solution. White and colored second "cover" coats of enamel are applied over the fired ground coat. For electrostatic enamels, the colored enamel powder can be applied directly over a thin unfired ground coat "base coat" layer that is co-fired with the cover coat in a very efficient two-coat/one-fire process.

The frit in the ground coat contains smelted-in cobalt and/or nickel oxide as well as other transition metal oxides to catalyze the enamel-steel bonding reactions. During firing of the enamel at between 760 to 895 °C (1,400 to 1,643 °F), iron oxide scale first forms on the steel. The molten enamel dissolves the iron oxide and precipitates cobalt and nickel. The iron acts the anode in an electrogalvanic reaction in which the iron is again oxidized, dissolved by the glass, and oxidized again with the available cobalt and nickel limiting the reaction. Finally, the surface becomes roughened with the glass anchored into the holes.^[23]

Gallery[link]

• 

  Early 13th century Limoges chasse used to hold holy oils; most were reliquaries.

• 

  Medallion of the Death of the Virgin, with basse-taille enamel

• 

  Silver, silver gilt and painted enamel beaker, Burgundian Netherlands, c. 1425-1450, The Cloisters

• 

  The Dunstable Swan Jewel, a livery badge in ronde bosse enamel, about 1400. British Museum

• 

  Louis George enamel watch dial

• 

  Iranian enamel

See also[link]

• Ceramic glaze
• Nineveh
• Rostov the Great - A city renowned for its enamel work.
• Staffordshire Moorlands Pan, a 2nd century bronze trulla.
• Franz Ullrich - Founder of a German enamelware factory.
• Fred Uhl Ball - American enamelist who created the largest known enamel mural.
• Vitreous china

Notes[link]

References[link]

• Campbell, Marian. An Introduction to Medieval Enamels, 1983, HMSO for V&A Museum, ISBN 0-11-290385-1

External links[link]

Wikimedia Commons has media related to: Enamel

• Pokany - Cloisonné Enamel
• Enamels on jewelry - historical
• Mechanical and Physical Properties of Vitreous Enamel
• VEA Vitreous Enamel Association (UK)
• Glass on Metal Magazine Online (US)
• CIDAE Center of Information and Diffusion of the Art of Enamelling (ES)
• Society of Dutch Enamellers (NL)
• The Enamelist Society (US)
• Guild of Enamellers, UK
• Porcelain Enamel Institute (US)
• International Enamellers Institute
• (INDIA)
• Enameller Darba Spars Ltd. (LV)

Antony Worrall Thompson
in November 2006
Born	Henry Antony Cardew Worrall Thompson (1951-05-01) 1 May 1951 (age 61) Stratford upon Avon, Warwickshire, England
Nationality	British
Occupation	celebrity chef, television presenter, radio broadcaster
Spouse	Jill (m. 1973-1978, divorced) Militza (divorced) Jacinta Shiel (m.?-present)
Children	5
Parents	Michael Ingham, Joanna Duncan

Henry Antony Cardew Worrall Thompson (born 1 May 1951)^{[citation needed]} is a British celebrity chef, television presenter and radio broadcaster.

Early life[link]

Worrall Thompson was born in Stratford upon Avon. His parents were actor Michael Ingham and actress Joanna Duncan, who separated when he was three.^[1] He was educated at The King's School, Canterbury, where he sustained facial injuries while playing rugby. He had to wait until he was twenty-one before he could have plastic surgery to correct the disfigurement.^[2]

Early career[link]

After he left school he studied hotel management at Westminster Kingsway College. Taking his first catering job in Essex, it is rumoured that his grandmother refused to write to him because she couldn't bring herself to write Essex on the envelope.^[3] In 1978, he moved to London and became sous-chef at Brinkley's Restaurant in the Fulham Road, becoming head chef one year later. The following year he took a sabbatical in France, eating and working his way around the local cuisine. After this he returned to England and started producing pans with his business partner Hassan.

Restaurants[link]

Worrall Thompson opened his first restaurant - Ménage à Trois - in Knightsbridge in 1981, notable for only serving starters and puddings.^[3] He then launched several successful restaurants, including Wiz and Woz in West London and Metro in Jersey — all of which reflect his somewhat individual approach to food. Until late 2006, he was Catering Director for Old Luxters Barn, in Buckinghamshire.

In February 2009, his restaurant holding company AWT Restaurants was placed into administration.^[4] Four restaurants closed - the Notting Grill in west London, the Barnes Grill in south-west London, together with two pubs in Henley-on-Thames, the Lamb Inn and the Greyhound with the loss of 60 jobs, Worrall Thompson personally bought back the remaining Windsor Grill in Berkshire, the Kew Grill in south-west London, and delicatessen the Windsor Larder.

It was revealed in April 2009 that Thompson's restaurant chain trouble was the result of its being "overstretched" and that his restaurants "had debts of more than £800,000 and owed 214 creditors money.^[5] Later in 2009, Thompson re-opened The Greyhound.^{[citation needed]}

Television[link]

Thompson made his first television appearance on BBC2’s Food and Drink, before appearing on Ready Steady Cook from 1994.

In 2003, he appeared in the second series of I'm a Celebrity... Get Me Out of Here!, which led to him replacing Gregg Wallace as the host of BBC2's Saturday Kitchen. The show transferred to BBC1 to replace Saturday morning children's television. However, after a large financial offer from ITV,^{[citation needed]} Worrall Thompson and the production company responsible for the show, Prospect Pictures transferred the format - including Australian wine expert Matt Skinner - to ITV from June 2006. The new show Saturday Cooks fared poorly against the new BBC production of Saturday Kitchen fronted by the younger James Martin, and retreated as Daily Cooks Challenge to now only air during the week. Since the move to ITV, Thompson has ceased to appear as a guest chef on Ready, Steady, Cook.

Worrall Thompson represented the Midlands and East of England in series one of the BBC's Great British Menu but was beaten by Galton Blackiston,^[6] after burning the meat course of his entry prior to the judging phase.

In June 2008 he made a guest appearance on ITV soap Emmerdale, where he was judging a Pub of the Year contest.

Awards and honors[link]

Worrall Thompson has won the Mouton Rothschild Menu Competition, and the Meilleur Ouvrier de Grande Bretagne (MOGB).^[3]

In February 2010, Worral Thompson was awarded only one star out of five after a food hygiene inspection at his gastro-pub, The Greyhound, near Henley-on-Thames. South Oxfordshire District Council said the score meant hygiene was "poor" with "standards generally low".^[7]

Criticism[link]

Worrall Thompson's recipe for Snickers Pie was nominated by independent food watchdog The Food Commission as one of the most unhealthy dessert recipes ever. Consisting of five Snickers bars, puff pastry, mascarpone, soft cheese, sugar and eggs, a single slice has been estimated to contain 1,250 calories.

Thompson recommended the poisonous plant Henbane as a "tasty addition to salads" in the August 2008 issue of Healthy and Organic Living magazine. Apologising for the error Thompson said: "I was thinking of a wild plant with a similar name, Fat Hen^{[disambiguation needed ]}, not this herb. It's a bit embarrassing, but there have been no reports of any casualties. Please do pass on my apologies." The magazine sent subscribers an urgent message stating that Henbane "is a very toxic plant and should never be eaten."^[8]

Personal life[link]

Worrall Thompson married Jill when he was 22; the couple divorced five years later. He subsequently married an Australian, Militza. The couple had two children and divorced. He is married to his third wife Jacinta Shiel, the couple live in High Wycombe and have two children.^[1] He has a child from a brief liaison.^[9]

In January 2012, Worrall Thompson received a formal police caution for shoplifting low value items, including wine and cheese from the Henley-on-Thames branch of Tesco on a total of five occasions.^[10][11]

Worrall Thompson is a patron of FOREST,^[12] a UK-based pro-smoking lobby. He claimed to have given up smoking in February, 2010, in a feature for Radio 4's Woman's Hour.^[13] He is also involved in fundraising for the Conservative Party and is an active supporter of National Family Week.^[14] In 2003, Worrall Thompson funded the Antony Worrall Thompson Trophy - a charity football cup played by 8 semi-professional teams in the summer, pre-season. However, due to Worrall Thompson's financial issues, the trophy lasted only one year and was never replayed after Altrincham F.C's 2003-2004 victory over Northwich Victoria F.C. Altrincham won the game 4-3. October 2010 saw Thompson join Uncovered (magazine) as a regular columnist offering recipes and advice on eating for good health and seasons finest produce.^[15]

References[link]

Notes

External links[link]

• Antony Worrall Thompson's website
• Antony Worrall Thompson's Restaurants website
• Interview with asrecommended
• Extract from his biography
• The Independent, 6 February 2005