The salting mixture of sodium chloride and water is introduced into the kiln when the appropriate temperature is reached, typically around 900 °C. As the kiln reaches higher temperatures, typically 1100-1200 °C, the sodium chloride vaporizes and reacts with steam to form hydrogen chloride and soda. These react with the silica in the body and other body constituents. A glaze of fairly high alumina content (0.6 molecular parts) and a relatively low silica content (2.6 molecular parts), and in which the main base is soda, is formed. Salt glazes have been improved by the addition of borax, and sometimes sodium nitrate, to the salting mixture. Colouring oxides can be incorporated in the salting mixture to give decorative effects, such as a kind of aventurine glaze.