and carved or incised designs in the body. Shapes were originally mostly simple, allowing the glaze colour to create the main effect of a piece, but in later periods raised decoration was common. Technical aspects and decoration The body of Longquan celadon, as seen in fragments under glaze, varies from "a heavy, compact grey stoneware to an almost white porcellaneous material", but where fired at the surface this turns to a typical terracotta reddish brown, seen at the unglazed foot of many pieces, and when relief decoration is left unglazed (see below and illustration). This distinguishes Longquan from Northern Celadons. However, this may not be the case in pieces made from the most whitish, porcellanous, material, where the fired body may also "be translucent if thin enough". In Western sources, individual pieces are normally classified as stoneware, but some may be called porcelain; material translated from the Chinese is likely to describe all as "porcelain". The body was normally thrown on the potter's wheel, with large vases often thrown in sections and luted together. Templates were used, and sometimes moulds, including two-part moulds, and moulds including decoration. Unglazed biscuit relief sections were achieved either by sprigging the reliefs over a glazed area before firing, where the surface would be flat in the kiln, or by adding a resist of wax or grease before glazing, when the sides of a vase were decorated. The glaze colours vary across a wide spectrum of greyish to blueish greens, with some yellowish browns as well. The colour comes from iron oxide fired in a reducing atmosphere, and the colour varies with the temperature and the strength and timing of the reduction. Longquan celadon was fired in long dragon kilns, brick tunnels rising up a slope, with a series of chambers, and the best results came from the pots in the uppermost stages, which heated up more slowly and evenly. Saggars were always used, and the longer kilns, with up to twelve chambers, might have been able to fire as many as 25,000 pieces at a time. The firing temperature was probably between 1,180 °C and 1,280 °C, with the range over 1,250 °C giving the best green or blue colours. In some cases at least there appear to have been layers of glaze and also multiple firings to achieve a deeper glaze effect. The glaze is made opaque by the presence of plant ash