factory closed in 1956, due largely to new clean air regulations that prohibited the production of salt glaze in the urban environment. Production, but not of salt glazing, was transferred to their factory in Burslem which had been established in 1877. Several other stoneware potteries also operated in Lambeth between the mid-18th & 19th centuries, including James Stiff and Sons and Stephen Green's Imperial pottery. The former having started his pottery career at Doulton in 1830, before opening his own factory in 1843. New world One of the first potteries in the US was on Bean Hill in Norwich, Connecticut. They manufactured yellow-brown, salt glazed earthenware. According to a rather dubious local legend, their salt glaze technique was discovered in about 1680 by a servant. There was an earthenware vessel on the fire with brine in it to cure salt pork. While the servant was away the brine boiled over, the pot became red hot, and the sides were found to be glazed. A local potter utilized the discovery and salt-glaze became established. The earliest known production of salt glaze pottery in Australia has been dated to 1850–1883. Process The salt glaze is formed on the unglazed body by reaction of common salt with the clay body constituents, particularly silica, toward the end of firing. The body should ideally be richer in silica than normal stoneware, and iron impurities can help produce good salt glazes. A reduction atmosphere can be employed as the reduced iron silicates are very powerful fluxes. The salting mixture of sodium chloride and water is introduced into the kiln when the appropriate temperature is reached, typically around 900 °C, or salt can be placed inside the kiln prior to firing. 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 vapors 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. Salt fumes in a firing atmosphere react in the following way: 2NaCl +