The purpose for which glazing is done are:
- To improve the appearance.
- To produce decorative effects.
- To provide smooth surfacing.
- To protect the surface from the action of atmospheric agencies.
- To make the particles durable.
The term porcelain is used to indicate fine earthenware which is white, thin and transparent. Clay of sufficient purity and possessing high degree of tenacity and plasticity is used for preparing porcelain. It is hard, brittle and non-porous. It is prepared from clay, feldspar, quartz and minerals. Porcelains are of two types – low-voltage porcelain and high-voltage porcelain. Low-voltage porcelain is prepared from dry process and high-voltage porcelain is prepared from wet process.
Porcelain enamelling is a common process for making the surface smoother, chemical proof and resistant to deterioration. The process involves fusing thoroughly the mixture of raw materials in a furnace and then grinding the mixture to a fine powdered stage. The material to be enamelled is then given a coating of this powder either directly by dusting the powder over the surface or by mixing the mixture with water and spraying on the surface. They are adopted for various uses like sanitaryware, electrical insulators, storage vessels, etc.