The _Ching-tê Chên T’ao lu_[432] is almost verbose on the subject of T’ang’s achievements. He had a profound knowledge, it tells us, of the properties of the different kinds of clay and of the action of the fire upon them, and he took every care in the selection of proper materials, so that his wares were all exquisite, lustrous, and of perfect purity. In imitating the celebrated wares of antiquity he never failed to make an exact copy, and in the imitation of all sorts of famous glazes there were none which he could not cleverly reproduce. There was, in fact, nothing that he could not successfully accomplish. Furthermore, his novelties[433] included porcelains with the following glazes and colours: foreign purple (_yang tzŭ_), cloisonné blue (_fa ch’ing_), silvering (_mo yin_), painting in ink black (_ts’ai shui mo_), foreign black (_yang wu chin_), painting in the style of the enamels on copper (_fa lang_), foreign colouring in a black ground (_yang ts’ai wu chin_), white designs in a black ground (_hei ti pai hua_), gilding on a black ground (_hei ti miao chin_), sky blue (_t’ien lan_), and transmutation glazes (_yao pien_). The clay used was white, rich (_jang_) and refined, and the body of the porcelain, whether thick or thin, was always unctuous (_ni_). The Imperial wares attained their greatest perfection at this time. The preface to T’ang’s collected works, which is quoted in the same passage, singles out as special triumphs of his genius the revival of the manufacture of the old dragon fish bowls (_lung kang_) and of the Chün yao, and the production of the turquoise and rose (_mei kuei_) colours in “new tints and rare beauty.” It is obvious from these passages that T’ang was responsible for many of the types enumerated in Hsieh Min’s list in the preceding chapter, not only among the reproductions of antiques but among the new inventions of the period, such as the cloisonné blue, foreign purple, silvering, painting in ink black, and foreign black. It follows, then, that these novelties could not have been made much before 1730, for T’ang was still at that time occupied chiefly with learning the potter’s art. It is equally certain that he continued to make a specialty of imitating the older wares during the reign of Ch’ien Lung, so that we may regard the best period of these reproductions as extending from 1730–1750.