Overglaze decoration, overglaze enamelling or on-glaze decoration is a method of decorating
pottery
Pottery is the process and the products of forming vessels and other objects with clay and other ceramic materials, which are fired at high temperatures to give them a hard and durable form. Major types include earthenware, stoneware and por ...
, most often
porcelain
Porcelain () is a ceramic material made by heating substances, generally including materials such as kaolinite, in a kiln to temperatures between . The strength and translucence of porcelain, relative to other types of pottery, arises mainl ...
, where the coloured decoration is applied on top of the already fired and
glazed surface, and then fixed in a second firing at a relatively low temperature, often in a
muffle kiln
A muffle furnace or muffle oven (sometimes retort furnace in historical usage) is a furnace in which the subject material is isolated from the fuel and all of the products of combustion, including gases and flying ash. After the development of ...
. It is often described as producing "enamelled" decoration. The colours fuse on to the glaze, so the decoration becomes durable. This decorative firing is usually done at a lower temperature which allows for a more varied and vivid
palette of colours, using pigments which will not colour correctly at the high temperature necessary to fire the porcelain body. Historically, a relatively narrow range of colours could be achieved with
underglaze
Underglaze is a method of decorating pottery in which painted decoration is applied to the surface before it is covered with a transparent ceramic glaze and fired in a kiln. Because the glaze subsequently covers it, such decoration is completely ...
decoration, where the coloured pattern is applied before glazing, notably the
cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
blue of
blue and white porcelain
"Blue and white pottery" () covers a wide range of white pottery and porcelain decorated under the glaze with a blue pigment, generally cobalt oxide. The decoration is commonly applied by hand, originally by brush painting, but nowadays by sten ...
.
Many historical styles, for example
mina'i ware
ware is a type of Persian pottery developed in Kashan, Iran, in the decades leading up to the Mongol invasion of Persia in 1219, after which production ceased. It has been described as "probably the most luxurious of all types of ceramic war ...
,
Imari ware
is a Western term for a brightly-coloured style of Japanese export porcelain made in the area of Arita, in the former Hizen Province, northwestern Kyūshū. They were exported to Europe in large quantities, especially between the second half o ...
, Chinese
doucai
''Doucai'' () is a technique in painting Chinese porcelain, where parts of the design, and some outlines of the rest, are painted in underglaze blue, and the piece is then ceramic glaze, glazed and fired. The rest of the design is then added in ov ...
and
wucai
''Wucai'' (五彩, "Five colours", "Wuts'ai" in Wade-Giles) is a style of decorating white Chinese porcelain in a limited range of colours. It normally uses underglaze cobalt blue for the design outline and some parts of the images, and overgla ...
, combine the two types of decoration. In such cases the first firing for the body, underglaze decoration and glaze is followed by the second firing after the overglaze enamels have been applied.
The technique essentially uses powdered glass mixed with coloured pigments, and is the application of
vitreous enamel
Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between . The powder melts, flows, and then hardens to a smooth, durable vitreous coating. The word comes from the Lati ...
to pottery;
enamelled glass
Enamelled glass or painted glass is glass which has been decorated with vitreous enamel (powdered glass, usually mixed with a binder) and then fired to fuse the glasses. It can produce brilliant and long-lasting colours, and be translucent or o ...
is very similar but on glass. Both these latter two are essentially painting techniques, and have been since they began. In contrast, on metal painting in enamel arrived very late, long after techniques such as
cloisonné
Cloisonné () is an ancient technique for decorating metalwork objects with colored material held in place or separated by metal strips or wire, normally of gold. In recent centuries, vitreous enamel has been used, but inlays of cut gemstones, ...
, where thin wires are applied to form raised barriers, which contain areas of (subsequently applied) enamel, and
champlevé
Champlevé is an enamelling technique in the decorative arts, or an object made by that process, in which troughs or cells are carved, etched, die struck, or Casting (metalworking), cast into the surface of a metal object, and filled with vitre ...
, where the metal surface is sunk to form areas where the enamel is poured.
In
Chinese porcelain
Chinese ceramics show a continuous development since pre-dynastic times and are one of the most significant forms of Chinese art and ceramics globally. The first pottery was made during the Palaeolithic era. Chinese ceramics range from construc ...
, enamels were and are sometimes applied to unglazed pieces; this is called "enamel on
the biscuit
The Gold Codes are the launch codes for nuclear weapons provided to the President of the United States in their role as commander-in-chief of the armed forces. In conjunction with the nuclear football, the Gold Codes allow the president to autho ...
" and similar terms.
History
![The Music Lesson MET DP-14272-001 (cropped)](https://upload.wikimedia.org/wikipedia/commons/2/24/The_Music_Lesson_MET_DP-14272-001_%28cropped%29.jpg)
Enamel was used in jewellery, applied to metal, from very early on - there are examples in the
Tomb of Tutankhamun
The tomb of Tutankhamun, also known by its tomb number, KV62, is the burial place of Tutankhamun (reigned c. 1334–1325 BC), a pharaoh of the Eighteenth Dynasty of Egypt, Eighteenth Dynasty of ancient Egypt, in the Valley of the Kings. The tomb ...
of c. 1325 BC. Enamel was also used to decorate glass by the time of the Roman Empire. Applied to pottery, it is first seen in Persian
mina'i ware
ware is a type of Persian pottery developed in Kashan, Iran, in the decades leading up to the Mongol invasion of Persia in 1219, after which production ceased. It has been described as "probably the most luxurious of all types of ceramic war ...
from the late 12th century, using a group of seven main colours. Presumably the potters learnt the technique from glassmakers.
Slightly later it appeared in
Chinese ceramics
Chinese ceramics show a continuous development since pre-dynastic times and are one of the most significant forms of Chinese art and ceramics globally. The first pottery was made during the Palaeolithic era. Chinese ceramics range from construc ...
in
Cizhou stoneware from as early as the 13th century, with
use on porcelain following within a century, though it did not become predominant until later, and the full possibilities were not realized until the 17th and 18th centuries in the
famille jaune, noire, rose, verte
Famille jaune, noire, rose, verte are terms used in the West to classify Chinese porcelain of the Qing dynasty by the dominant colour of its enamel palette. These wares were initially grouped under the French names of ("green family"), and (pink ...
group of palettes. Some techniques use thin metal leaf, including mina'i ware as well as the more usual pigments, which are typically applied in a liquid or paste form, painted by brush, or using
stencil
Stencilling produces an image or pattern on a surface, by applying pigment to a surface through an intermediate object, with designed holes in the intermediate object, to create a pattern or image on a surface, by allowing the pigment to reach ...
s or
transfer printing
Transfer printing is a method of decorating pottery or other materials using an engraved copper or steel plate from which a monochrome print on paper is taken which is then transferred by pressing onto the ceramic piece. Fleming, John & Hugh H ...
. The Japanese
kakiemon
is a style of Japanese porcelain, with overglaze decoration called "enameled" ceramics. It was originally produced at the factories around Arita, in Japan's Hizen province (today, Saga Prefecture) from the Edo period's mid-17th century onwards ...
style, and other Japanese styles, used the technique from at least the second half of the 17th century. The technique was also developing in Europe, firstly in what the French called ''petit feu''
faience
Faience or faïence (; ) is the general English language term for fine tin-glazed pottery. The invention of a white pottery glaze suitable for painted decoration, by the addition of an oxide of tin to the slip of a lead glaze, was a major ad ...
, and in the 18th century in porcelain, and there appears to have been some influence in both directions between Asia and Europe. From about 1770 to the mid 20th century it was the dominant decorative technique in expensive pottery, mostly porcelain, made in Europe, East Asia, and (to a lesser extent) North America.
In 18th-century England, where the technique was developed, the earliest forms of
transfer printing
Transfer printing is a method of decorating pottery or other materials using an engraved copper or steel plate from which a monochrome print on paper is taken which is then transferred by pressing onto the ceramic piece. Fleming, John & Hugh H ...
on pottery, for example by Sadler & Green in
Liverpool
Liverpool is a city and metropolitan borough in Merseyside, England. With a population of in 2019, it is the 10th largest English district by population and its metropolitan area is the fifth largest in the United Kingdom, with a popul ...
, were overglaze, although by the end of the century it was normal to print as underglaze.
Today overglaze decoration is much less commonly used, other than in traditionalist wares, as the range of colours available in underglaze has greatly expanded.
Muffle kilns
The kiln used for the second firing is usually called a muffle kiln in Europe; like other types of
muffle furnace
A muffle furnace or muffle oven (sometimes retort furnace in historical usage) is a furnace in which the subject material is isolated from the fuel and all of the products of combustion, including gases and flying ash. After the development of ...
s the design isolates the objects from the flames producing the heat (with electricity this is not so important). For historical overglaze enamels the kiln was generally far smaller than that for the main firing, and produced firing temperatures in the approximate range of 750 to 950 °C, depending on the colours used. Typically, wares were fired for between five and twelve hours and then cooled over twelve hours.
[Hughes, 34-35]
Notes
References
*Hughes, G Bernard, ''The Country Life Pocket Book of China'', 1965, Country Life Ltd
*
Needham, Joseph (ed), ''Science and Civilisation in China'', Volume 5, Part 12, 2004, Cambridge University Press, , 9780521838337
google books
*Vainker, S.J., ''Chinese Pottery and Porcelain'', 1991, British Museum Press, 9780714114705
*Watson, Oliver, "Pottery under the Mongols" in ''Beyond the Legacy of Genghis Khan'', 2012, BRILL, Ed. Linda Komaroff, , 9789004243408
google books
{{Ceramics-stub
Types of pottery decoration