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About the glaze

The surface of ceramic is porous. In order to protect these from penetration of water, dirt and gases (smells), it is glazed. The glaze is a usually colorless coat which consists predominantly of the components of glass and connects in the smooth fire inseparably with the ceramic. Figures are usually only glazed because it looks better. The glaze on other pieces, for example table-ware, has beside the optical a hygienic job. In the range of sanitary ceramic the hygiene and cleaning is in the foreground. The glaze had their origin however in the use on table-ware. Apart from the aesthetic effect of effect glazes and a more transparent of the porcelain serves these to be able to clean the closed and smoothed surface better. Furthermore the glazed surface becomes much more protection against mechanical influences as for example knife cuts. So has the glazed hard porcelain after a uniform testing method of Friedrich Mohs, which it developed approx 1812 (DIN EN 101), a hardness from approx 7. To the comparison has for example copper or brass a hardness of 2-3, marble of 3, iron of 4 or Bodenfliesen and / or steel a hardness of 5. Those all would be under the hardness of the glaze. Nevertheless a glaze can be damaged. Here primarily are two problems by the table-ware. The glaze can scratch if you put not glazed ceramic on them (for exampel if you strack plates). The other problem is the cleaning with strong chemical in a dish-washer. A chemically attacked glass or glaze shows a grey-blue veil, which does not let itself eliminate. The surface is blunt and " blind". These damage you can´t repair once more. Ceramic can show so-called Craquelé, grid tears in the glaze. These can be a symptom of old age. Some pieces are manufactured however with Craquelé as decoration.