A glassy coating on the surface of a ceramic product, or a mixture of materials that, after application and firing, gives this coating. The basis of the glaze is quartz, feldspar, kaolin, marble or chalk, dolomite, clay. Color is achieved by introducing small amounts of metal oxides and salts.
Glaze is a shiny or enamel glassy layer in the form of a thin film (0.1 - 0.3 mm). The chemical composition of the glaze and the ceramic shard is different. Their thermal expansion also varies in size. For strong adhesion of the glaze layer to the shard, one must strive to ensure that the thermal expansion of the glaze and the shard is equal.
Some ceramic glazes contain lead and other hazardous elements. The authors suggest replacing them with less harmful analogues. The article describes various types of lead-free glazes, their compositions, properties and manufacturing methods. Particular attention is paid to decorative effects.
The reasons for the appearance may be the following factors:
- thermal shock;
- insufficient drying of the cement base;
- excess cement content in the layer...
The metals lead - Pb and cadmium - Cd are sometimes included in the glaze of ceramic tiles and pose a danger to human health.
