The interesting list of wares made at the Imperial factory which is given in detail on pp. 223–226 supplies a full commentary on this meagre notice, illustrating the types which are merely hinted in the _T’ao lu_ and specifying the particular kinds of antiques which were reproduced and many of the new processes invented in this reign. With regard to the last, however, it appears that the chief credit was due to Nien’s gifted assistant, T’ang Ying. Most of the actual processes, such as carving, engraving, piercing _à jour_, embossing in high and low relief, blowing on of the glazes, painting in enamels, in gold and in silver,[372] have already been described in previous chapters. Indeed we may assume that all the science of the K’ang Hsi potters was inherited by their successors in the Yung Chêng period, and we need only concern ourselves with the novelties and the specialities of the period. A few words should be said first about the ware itself. Necessary variations in the appearance of the Ching-tê Chên porcelain, which were due to purely natural causes such as the use of clays of varying qualities or those from different localities, have been noted from time to time. These differences are generally quite obvious and they explain themselves. But apart from these there are numerous instances in which the potters have deliberately departed from the normal recipes in order to obtain some special effect. Thus we saw that the _ch’ing-tien_ stone was introduced into the body in imitations of the opaque and rather earthy-looking white Ting Chou ware; _hua shih_ (steatite) was used for another type of opaque porcelain which offered a vellum-like surface to the blue painter; and coarse, impure clays were found of great service in the imitation of the dark-coloured body of the antique wares.