Chinese earthern ware

Ceramics are objects shaped from earthen materials and fired in a kiln to make them water-proof and durable to a certain extent. The basic materials for ceramics are mineral-rich clay, containing kaolinite, silica and feldspar. The crystal structure of these minerals allows a plastic forming of the clay, making it possible to create every thinkable shape that does not decay during the firing process. After blending of raw materials according to special recipes, the vessel is formed upon a rotating wheel, if the vessel shall be round. In the kiln, the ready made earthenware objects are gradually heated from room temperature through a hot zone, and back to room temperature to achieve some measure of bonding of the silica particles, consolidation of the object's shape and reduction in porosity. Refinement of the earthenware can either be reached by vitrification of by glazing. Vitrification can be reached through a change of the silicate's crystal structure into an amorphous glass structure, and it happens at very high firing temperatures between 1,500 and 1,800°C (2,900 and 3,200°F) that can be lowered by fluxing agents. Glazing is made by dipping the fired object into - or painting it with - a glazing slurry and firing it again at a somewhat lower temperature than the main firing. By the addition of special metallic oxides, the vessels are given colors of a relatively small range.