The practical advantages of transparent glazes are that they give a smooth, easily cleaned and therefore hygienic surface. They will also be your best chance of getting a glaze to fit the body without crazing. Their potential disadvantage, however, is that the underlying clay will show through and, indeed, the colour of the body will be developed by the 'wetting' action of the glaze. This is just the same as enhancing the colour of dry pebbles and rocks by placing them in a bowl of water. With 'whiteness' very much at a saleable premium, potters developed white opaque glazes to cover the clay as seen, for example, in tin-glazed maiolica and bathroom tiles. Even porcelain and white earthenware bothes have a slightly greyish cast in comparison with the ultra whiteness that can be provided by opacified glazes. The three most frequently used materials for opacifying transparent glazes are tin oxide, titanium dioxide and zirconium silicate. In the cases of tin oxide and zirconium silicate the opacity comes from the oxides remaining as finely suspended particles. With titanium dioxide, however, the opacity arises from the formation of crystals.
展开▼
