A Sliplike glaze produced during the Etruscan and Greek periods. A deflocculant, such as Calgon, is added to the slip so that the finer particles of clay can be decanted off and collected. It can be applied by brushing or spraying to greenware or bisque. After applying, the surface is burnished with a chamois or metal spoon. When dried, terra sigillata gives a wax like surface which is not completely waterproof. Terra sigillata made from grolleg clay, along with other types or kaolin clays, can be fired as high as cone 10. All other types of terra sigillata are best when fired at bisque temperatures.