In salt firings the glaze is created by the action of common salt, introduced into the kiln at the end of the firing, on the surface of the pots. The salt vaporises and is carried through the kiln by the flames, reacting with the silica and alumina in the clay to form a glaze from the clay surface. Depending on the silica-alumina balance in the clay this glaze can vary from smooth and silky to the characteristic dimpled surface commonly referred to as ‘orange peel’.
Salt glazing as a technique originated in 15th century Germany, when, it is said, the potters of the Westerwald region started fuelling their kilns with the salt impregnated wood taken from boxes used for preserving fish and meat. From this happy accident sprang an industrial process used in Europe up until the 1950s to produce all kinds of ceramics from sewer pipes to high status tableware. The technique is now the preserve of studio potters and ceramic artists and has a following that is particularly strong in Europe, Australia and North America.