Engobe
,_Gelduba_Grab_5555,_Museum_Burg_Linn.jpg)
The engobe (also known as casting compound or casting compound) is a generic term for a thin-bodied clay mineral compound that is used to color or coat ceramic products. These can be slurries (French barbotine ), but mixed forms between slurry and glaze or coating masses without slip are also referred to as engobes. Unlike glazes, engobes do not form a protective layer for the ceramic product.
history
Engobes have been used for practical and aesthetic reasons since the late Stone Age. For example, graphitized engobes were applied in the Urnfield and Hallstatt times to give the clay pot a metallic appearance. In ancient times, for example, in the first century BC, the Romans covered clay vessels with a thin layer of the finest slip. This coating gave the vessels from this Terra Sigillata their typical red matt, glossy surface. In the Roman Empire , engobes were then used for so-called engobed goods : very thin-walled earthenware was covered with a usually matt engobe.
Application method
Engobes can be made from any type of clay and in different firing colors. Often substances are added that are also contained in glazes and that create a glass phase in the fire. Other additives are used to color the engobes. In addition to the different firing colors of the clays, other pigments or z. B. Metal oxides are added to achieve a color effect. Engobes adhere better to leather-hard or dry, unfired clay than to scalded body. After drying, the engobe combines with the broken glass in the fire. On the other hand, engobe that is applied too thickly on scalded cullet forms its own body, which contracts with the shrinkage during drying and therefore flakes off the already shrunk, scalded cullet.
Own engobe
The slip that is created when the clay is formed on the turntable is called its own engobe. This is often used as a primer for subsequent painting.
Basic robe
If it is a flat engobe that differs in color from the body and is possibly also applied on both sides, which serves as a painting or glaze base, one speaks of a basic gobe. Engobe with white firing color can be used to cover a colored, burning body and thus create a base for a glaze. Many glazes only come into their own on a white background. At the same time, a body that does not burn white can have better properties in terms of stability and malleability. That is why engobe made from white burning clay is often used as a buffer layer between the clay body and the glaze. In order to produce a smooth surface, a fine-grained slip is obtained by means of blow-down. It is useful to have an approximately similar coefficient of expansion of the engobe and the body below.
Sintered engobe
A sintered engobe is a combination of coloring and glazing elements, for example metal oxides or pigments consisting of chalcogenides ; it is engobe and glaze in one and has a slightly shiny surface. As a rule, engobes are matt after firing and form a porous surface without gloss. By adding fluxes or illitic clays to the slip, the engobe gets a higher alkali content. This reduces the viscosity of the engobe during the fire and a shiny, closed layer is formed. By using extremely fine clays, you can also achieve a glossy surface, as these start to sinter at lower temperatures.
Painting robe
If it is a colorless or colored clay slip, which for decorating with the Malhorn is applied, so one speaks of a Malengobe.
Green body, light gray / light cream burning clay, completely covered with black engobe, incised decor, condition after drying
Green body, light gray / light cream burning clay, completely covered with engobe with blue pigment, incised decor, condition after drying
Painted with gray engobe
Painted with gray and blue engobe
Painted with gray, blue and green engobes
green pigmented engobe, Japanese brush for application, modeling wood
Engobe painting
.JPG)
A decorative slip application with a brush or a paint horn is called engobe painting, slip painting or painting horn decor. Depending on the thickness of the applied layer, this can be done either on the leather-hard or unfired, dry clay or, if the application is very thin, it can also be done on the scalded shards . In addition, after the biscuit firing, the body can be coated with a transparent glaze to create a smooth, shiny and waterproof surface.
Industrial application
Engobing is also an industrial process for the color design of ceramic surfaces. The blank ( tile , roof tile ) is coated with mineral clay slurry by dipping, pouring or spraying. Different color effects can be achieved depending on the application technique. When the blank is subsequently fired, the sludge sintered and results in a matt to matt-glossy surface.
literature
- Wolfgang Hackspiel: The manufacture of the Lower Rhine earthenware . In: Joachim Naumann (Ed.): Keramik vom Niederrhein , Cologne 1988, ISBN 3-927396-00-1 , pp. 255ff.
- Wolf Matthes: Engoben , Koblenz 2006.
- Hermann Salmang, Horst Scholze, Rainer Telle (eds.): Ceramics , 7th edition, Heidelberg 2007.
Web links
Individual evidence
- ^ Frank Hamer, Janet Hamer: The Potter's Dictionary , University of Pennsylvania Press, 2004, p. 126.
- ↑ Hermann Salmang, Horst Scholze, Rainer Telle (eds.): Ceramics , 7th edition, Heidelberg 2007, p. 676.
- ↑ Hamer: The Potter's Dictionary , p. 42.
- ^ Salmang, Scholze, Telle: Keramik , p. 676.
- ^ Salmang, Scholze, Telle: Keramik , p. 676.