History of Vitreous Enamel
The word enamel comes the High German word 'smelzan' later becoming 'esmail' in Old French. Hence the current usage of 'smalto' in Italian, 'email' in French and German and 'enamel' in English.
It is thus defined as a vitreous, glass-like coating fused on to a metallic base. In history, enamels were initially applied on firstly gold, then silver, copper, bronze and more latterly on iron and steel. The term is also used for the application of decorative fusible glass applied to glass objects.
The earliest known enamelled objects were made in Cyprus in around the 13th century BC during the Mycenæan period. Six gold rings discovered in a Mycenæan tomb at Kouklia were decorated with various vitreous coloured layers fused on to the gold.
Earlier decoration of metal objects with glass, along with other materials such as precious and semi-precious stones, such as those found in the tombs of ancient Egypt relied on cementing the glass to the metal or a mechanical fixing by clasps. It was not until this unknown craftsman in Cyprus discovered that by fusing the glass on to the metal that the art of vitreous enamelling was born. The rings are chased gold, with an ornamentation of twisted square wires and it is almost certain that the glass was laid into the cells as very carefully cut pieces. These together with a gold sceptre and orb decorated with white pink and green are the earliest known pieces of enamel and can be found in the Nicosia museum in Cyprus.
This was the forerunner of the development of the Cloisonné technique for enamelling, where strips of gold, silver, copper or brass are attached to the metal base to form a network of small raised cells to form a border into which the enamel is laid, often as a paste. The final thickness is built up in layers with intermediate firings. In this way the ‘cloisons’ (the cells) prevent diffusion of the colours of the enamel and also give the mechanical adhesion of the enamel. When the enamel thickness is complete the cloisons are only visible as a fine network within the enamel. The final process involves grinding to smooth the enamel level with the tops of the cloisons and a polish to bring out the true colours and finish.
Cloisonné techniques pre-date enamel to 4000 BC and was employed as a method of setting semi precious stones into jewellery by cold cementing. This was used widely by the ancient Egyptians, one of the most famous pieces being the gold mask of Tutankhamun, which may look as if it is enamelled, but in fact, it is not - the artist has used this early cloisonné method. Filigree work is a development of this technique.
Unfortunately there are only a few remaining enamelled relics from this very early period. It is likely that the craft spread to the ancient Greeks and via them to Europe. A 5th century BC Greek hair ornament shows remarkable skill, decorated on to gold and silver. Shield shapes around a lion’s neck are enamelled. This piece is in the museum in Birmingham. Apart from a very few pieces such as this, the Greeks are not well known for their enamels.
When Caesar conquered Britain, he found that the Celts were already using enamels and many examples of this early craft are in museums all around the British Isles with some very good examples in the British Museum. There is a mirror in Gloucester museum found at Birdlip in Gloucestershire with red enamel. They had used the champlevé technique, where a recess in the metal, either produced by casting, chasing or engraving is filled with opaque red, blue, white and green enamel. The enamel is polished flush with the divisions formed by the edges of the cells. The later Saxon hanging bowls found in the Sutton Hoo boat burial are some of the finest early champlevé work.
In the 9th Century AD Cloisonné technique enamels moved back into the Middle East in Byzantine Constantinople and a century later into Russia. The Byzantine style continued until the 12th Century and usually comprised small thin pieces of gold, which were set into much larger objects. One of the finest is an 11th century plaque of St Paul, which is in the Victoria and Albert Museum. Some two centuries later the Rhine, Meuse and Limoges areas were already producing some of their best work. The Limoges area also produced enamel work by the champlevé technique, continuing well into the 14th century AD.
A newer technique was developed in Italy in the 13th Century. Known as Basse-taille, a translucent or transparent enamel is applied over a low relief, sunken or intaglio design, usually in gold or silver. The earliest known reference to this is in 1286 but the earliest known piece dates from 1290, a gold chalice made for the Convent of St Francis of Assisi.
The collections of the great cathedrals and churches account for the survival of these early works. A rare piece known as the King’s Lynn Cup or sometimes as the King John’s Cup is on display at King’s Lynn. It has been much restored over the years, but it originally dates to 1325 and is almost certainly the output of an English workshop. The Royal Gold Cup of the Kings of France and England was certainly made in Paris in 1380-1390 and may be found in the British Museum, where it is one of the most important treasures. This piece, although restored and added to, still shows the original colours as vibrant as the day that it was first fired. It is one of the best examples of the durability and longevity of enamels.
By the 15th Century the skills of enamellers were gaining in complexity. The earliest known use of the plique-a-jour technique was in the 13th Century. The technique involves the use of translucent or transparent enamels fused to form a span across a network of cells, without a backing under the enamel. The enamel is thus the structure of the piece – a shell supported within the network of metal cells. It is similar to cloisonné but without the base support. Often a temporary backing is used to support the enamel during the firing and then it is removed by dissolving or polishing when the piece is complete. This is undoubtedly the most difficult technique of enamelling, but the results can be very spectacular. The silver gilt Mérode cup in the Victoria and Albert Museum dates from the 15th Century and is thought to be of Flemish or Burgundian origin. It is the only known piece of plique-a- jour from this early period.
The Limoges area of France, already well skilled in Champlevé techniques, adapted the skill developed by the Venetian glass makers of painting enamels onto glass by painting enamels onto metals. This technique, adopted in the 15th Century, did not require the complex divisions or engraving and led the way forward to a method which with only slight modifications is still used by art enamellers today.
Until the 18th Century nearly all enamelling involved the production of works of art and religious artefacts.
Enamel work of these early eras is now highly valued and later names such as Faberge and Battersea became synonymous with the special appeal of vitreous enamel. The first enamelling of iron is thought to have taken place in Germany around 1840 when the inside surface of cooking pots were coated with what we now call vitreous enamel. The metal base was cast iron and the enamel was applied in two coats. The application of the enamel was by dusting on to hot metal. The pot was then reheated and after full fusing of the enamel, the second layer was applied in the same way. The next stage of development was the use of a wet slurry of enamel by dipping. This was a major breakthrough and allowed the coating of much more complex shapes. By the end of the 18th Century, semi mass production of enamelled cast iron cooking vessels was being carried out, together with underground cast iron piping, wrought iron steam piping and other domestic vessels. Attention then turned to the enamelling of bathtubs and other sanitary ware. The longevity and desirability of the "Victorian" cat iron bathtub remains today.
About the turn of the century efforts turned to the enamelling of the new product, sheet steel, which had been produced as a result of the development of the Bessemer process for the production of steel. The developments which took place at that time laid the basis for the vitreous enamel that we know today. The solution of the problems of applying vitreous enamel to sheet steel was responsible for the large-scale industrialisation of the process. The main breakthrough was in the discovery that cobalt incorporated into the enamel is a major factor in developing adhesion between the steel and the enamel. Vitreous enamelling was, and to a large extent is still, applied in two coats. The first coat comprises a glass, which contains cobalt and nickel, which develop this adhesion. These enamels, called ground coats, tend to be blue black or bark brown. After firing this coat, a second coat is applied to give the final colour and properties. The application on to this by masking or screen-printing led to the development of enamelled signage in the early 20th century. This is still a major sector of the enamelling industry with an easy to clean finish, which is weather resistant and graffiti resistant. The survival of signage, some of which is now more than 100 years old, is witness to the durability of the product. Alongside was the development of the badge and medal industry, largely in the Birmingham area, a very specific expertise which continues to the present day.
The cooker and appliance industry soon realised that this material would give the ideal combination of properties that they also required - heat resistance, easy to clean and good looking in a range of colours. Major enamelling plants were set up and some of the names that are still recognisable today were foremost in push for development of new colours and new processes of mass production - names such as New World, Cannon, Tricity, English Electric, Stoves and Sidney Flavel are just a few. During the 1930's the use of sheet steel on cookers grew exponentially and the cooker became a must-have for the modern housewife. During the 1950's research into producing white enamel which could be applied direct to the steel without the need for a ground coat. This required a steel that was virtually pure iron. A complex acid pretreatment followed by a nickel application was required with very close process controls. Most appliance plants introduced this process during the 1960's. However, increasing costs and environmental factors which became overriding in the latter party of the 20tth Century required further developments. In the 1970's the process of electrostatic application of specially treated powder enamel was introduced. This permitted an even greater degree of automation and deskilling of the process with consequent major coat savings. The need to reduce the environmental impact of the complex pretreatment resulted in a return to a two-coat process.
The new enamels which were developed for the ground coat were capable of producing adhesion on steel which required no pretreatment other than removal of grease and oils used in production of the parts. Modern plants now apply the ground coat and the cover coat consecutively without an intermediate firing operation. The two layers are fired at the same time to produce the final vitreous enamelled part. This is the fully automated process which is in general use in all mass production plants today. Both wet and powder processes have been developed using this technology.
Smaller batch plants such as signage, flue pipes still use a two coat process involving two firing operations as it is not cost effective for small quantities if dissimilar parts to be produced using the automated technology. Specialist products such as storage silos and chemical reactor vessels will require multiple layers of enamel with intermediate firing operations s to produce the required resistant properties.
There is still a significant amount of decorative enamelling carried out on badges, jewellery and giftware.
Vitreous enamel, with its unique combination of appearance, range of beautiful colours and resistant properties, will still be part of life for the foreseeable future.