If the old potters had had to rely only on the thrower’s wheel for their shapes, no improvement in whiteness of ware, or in the salt glaze, would have availed much to increase the demand for earthenware. The development of the various use of moulds became of the greatest importance. The six workmen required at such a potworks, as is shown on the 1710 list, would be—slipmaker, thrower, turner, “stouker,” to put on handles and spouts, fireman and warehouseman. A good workman, such as the master, could throw, turn and stouk. But the fresh developments of the salt-glazed stoneware arising from the use of moulds converted potting into a specialized industry. We have seen that Elers used metal seals to press his ornamental “spriggs” on to his teapots. Such metal moulds could only be used for small articles or ornaments, for the mould stuck to the clay, and had to be carefully oiled. Both for the “sprigging on” of ornaments, and for the shaping of ware, a new form of mould was wanted. At first the alabaster of Derbyshire supplied the want. It was carved into shaped blocks, and from the blocks were made “pitcher,” or porous clay moulds, which could be replaced when worn out from the blocks, and could be used in various ways for the manufacture of ware: for sprigging, pressing, or “casting.” Then—a last step—about 1745, Ralph Daniel, of Cobridge, brought from France the secret of plaster of Paris moulds which replaced both pitcher and alabaster.[51] Under competition, the Staffordshire potters were getting critical. The white salt-glazed ware was competing with Chinese porcelain, and had to be made as thin and light and transparent as possible. The ware made by pressing the clay into the moulds sufficed for plates, basins and any lead-glazed ware, but it came out much too heavy for complicated shapes such as sauce-boats, teapots and vases, etc. To get these shapes Elers would have had them thrown and turned down in the lathe: they would all have been round. The process known as “casting” in a mould produced a finer result, and gave infinite scope for variation. In casting, the clay is run in a liquid form into a porous mould. After standing a few minutes, the slip is run out again, leaving behind a clay shell. This “cast” shell, taken out when dry, may be as fine and as varied in shape as the skill of the potter and the heat of his furnace will permit.