The lightest shade of this colour is what has been described as Nanking yellow.[352] It is used as a monochrome or as a ground colour with panels usually of _famille verte_ enamels, and sometimes with enamelled decoration applied over the brown glaze itself. It is clear that the _sui yu_ or crackle glaze was sometimes mixed with the _tzŭ chin_, for we find many examples of beautiful lustrous brown crackle. They have, however, in many cases an adventitious tinge of grey or green, for which the crackle glaze is perhaps responsible. A near relation to the _tzŭ chin_ (brown gold) glaze is the _wu chin_ (black gold), a lustrous black glaze obtained by mixing a little impure cobaltiferous ore of manganese (or coarse blue material[353]) with the _tzŭ chin_ glaze. Like the latter the black is an intensely hard glaze fired in the full heat of the great kiln, and it has a lustrous metallic surface which earned for it the name of “mirror black.”[354] This glaze seems to have really been a K’ang Hsi innovation,[355] and possibly it was a confusion with this fact which led d’Entrecolles into his erroneous statement about the date of the lustrous brown. [Illustration: Plate 112.--Three figures of Birds, late K’ang Hsi Porcelain, with coloured enamels on the biscuit. Fig. 1.--Stork. Height 17¼ inches. _British Museum._ Fig. 2.--Hawk. Height 10 inches. _S. E. Kennedy Collection._ Fig. 3.--Cock. Height 13½ inches. _British Museum._] [Illustration: Plate 113.--Porcelain delicately painted in thin _famille verte_ enamels. About 1720. Fig. 1.--Dish with figures of Hsi Wang Mu and attendant. Ch’êng Hua mark. Diameter 6¾ inches. _Hippisley Collection._ Fig. 2.--Bowl with the Eight Immortals. Diameter 8⅞ inches. _S. E. Kennedy Collection._] [Illustration: Plate 114.--Hanging Vase with openwork sides, for perfumed flowers. _Cumberbatch Collection._ Porcelain painted in late _famille verte_ enamels. About 1720. Blackwood frame. Total height 17 inches.] The mirror black is usually a monochrome tricked out with gilt traceries, but as in the case of the powder blue the light Chinese gilding is usually worn away, and often its quondam presence can now only be detected by a faint oily film which appears when the porcelain is held obliquely to the light. It is a common practice to have this lost gilding replaced by modern work.