As to the still older wares, those of Ch’ai and of Ju, which generally hold the place of honour in Chinese lists, it was of the first that the emperor spoke when he commanded that pieces intended for his own use should be clear as the sky after rain; but no specimen of this porcelain was extant even in Ming times. Its place, it would seem, was taken by the JU YAO (the word _yao_ is about equivalent to our term ‘ware’), which, like the Ch’ai, came from the province of Honan. This ware also is now practically extinct; Tzu-ching, however, claims to have possessed some specimens, and of these he gives more than one illustration. The glaze was thick and like melted lard (a comparison often made by the Chinese), and varied in colour from a _clair-de-lune_ to a brighter tint of blue. The name Ju, we may add, is often applied to more modern glazes which resemble the old ones in colour and thickness.
The name KUAN YAO, which means ‘official’ or ‘imperial’ porcelain, has been the cause of much confusion; the term has been applied to any ware made for imperial use. That of the Sung dynasty was made in the immediate neighbourhood of the imperial court, first at Kai-feng Fu and later at Hangchow. In its more strict use the term Kuan yao is applied to pieces generally of archaic form, to censers ornamented with grotesque heads of monstrous animals, and to wares of other shapes copied from old ritual bronzes. The glaze varies in colour from emerald green to greyish green and _clair-de-lune_, it is generally crackled, the cracks forming large ‘crab-claw’ divisions. Other kinds are described as white and very thin, but of these, perhaps for one of the reasons given above, no examples have survived to our day.
LUNG-CHUAN YAO and KO YAO. It will be convenient to class together these two most important types of Chinese porcelain. At the present day these names are applied in China to some comparatively common varieties of porcelain, not necessarily of any great age. But more strictly Lung-chuan yao is the term used by the Chinese for the heavy celadon pieces, whether dating from Sung or from Ming times, which were the first kinds of porcelain to become a regular article of export; while the word Ko yao is used as a general name for many kinds of crackle ware, which may vary in colour from white to a full celadon. In a more restricted sense it includes only the early pieces with a greyish white glaze and well-marked crackles.