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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 durable, and it also allows the production of pottery with a surface that has a uniform sheen.
Underglaze decoration is applied before the glaze, usually to unfired pottery ("raw" or "greenware") but sometimes to "biscuit"-fired (an initial firing of some articles before the glazing and re-firing). [10] [11] [12] A wet glaze—usually transparent—is applied over the decoration. The pigment fuses with the glaze, and appears to be ...
Italian Renaissance maiolica, Faenza, istoriato ware by Baldassare Manara, after Giovanni Antonio da Brescia, c 1520 -47. In-glaze or inglaze is a method of decorating pottery, where the materials used allow painted decoration to be applied on the surface of the glaze before the glost firing so that it fuses into the glaze in the course of firing.
Most pieces use only one of underglaze or overglaze painting. [15] Underglaze painting requires considerably more skill than overglaze, since defects in the painting will often become visible only after the firing. [14] During firing even refractory paints change color in the great heat. A light violet may turn into a dark blue, and a pale pink ...
The firing temperatures of such glazes are low, in the region of 950 – 1000 °C because of the variable degrees of solution of the individual oxides. [8] The amount of tin oxide used for coloured glazes depends upon the opacifying property of the chosen chromophore and the intensity of the colour desired; if a deep colour is required less ...
Crazing is a spider web pattern of cracks penetrating the glaze. It is caused by tensile stresses greater than the glaze is able to withstand. [1] [2] Common reasons for such stresses are: a mismatch between the thermal expansions of glaze and body; from moisture expansion of the body; and in the case of glazed tiles fixed to a wall, movement of the wall or of the bonding material used to fix ...
This can be done over or under the ceramic glaze, but the underglaze ("underprinting") method gives much more durable decoration. The ceramic is then glazed (if this had not been done already) and fired in a kiln to fix the pattern. With overglaze printing only a low-temperature firing was needed.
Sui and early Tang figures, before sancai was used, normally have the transparent glaze. [34] The application of the coloured glazes can be very variable; in many pieces the colours are carefully applied to different parts of the figures, but in others "they have been splashed on without regard for design or contour". [35]