All these blues were used either for painting under the glaze or for mixing with the glaze to form ground colours or monochromes, which varied widely in tint, according to the quantity and quality of the cobalt, from dark violet blue (_chi ch’ing_) through pale and dark shades of the ordinary blue colour to slaty blue and lavender. Some of them--notably the lavender and the dark violet blue--are often associated with crackle, being used as an overglaze covering a greyish white crackled porcelain. This treatment of the surface is well illustrated by a small covered jar in the British Museum with a dark violet blue apparently uncrackled but covering a crackled glaze. Two lavender blue bowls in the Hippisley Collection with the Chêng Tê mark are similarly crackled. Other Ming blue monochromes are a small pot found in Borneo and now in the British Museum with a dark blue of the ordinary tint used in painted wares, and a wine pot in the same collection with dragon spout and handle of a peculiar slaty lavender tint strewn with black specks, the colour evidently due to a strain of manganese in the cobalt. Next in importance to the blue is the underglaze red derived from copper, which was discussed at length in connection with the Hsüan Tê porcelains.[224] Its various tints, described as _hsien hung_ (fresh red), _pao shih hung_ (ruby red), and cinnabar bowls “red as the sun,” are, we may be sure, more or less accidental varieties of the capricious copper red. The same mineral produced the _sang de bœuf_, maroon and liver reds, and probably the peach bloom[225] of the K’ang Hsi and later porcelains. Other colours incorporated in the high-fired glaze in the Ming period are the pea green (_tou ch’ing_) or celadon, and the lustrous brown (_tzŭ chin_) which varied from coffee colour to that of old gold. Both of these groups derived their tint from iron oxide, carried in the medium of ferruginous earth. The use of two or more of these coloured glazes on one piece is a type of polychrome which was doubtless used on the Ming as on the later porcelains. The glazes fired at a lower temperature, in the cooler parts of the great kiln, and known for that reason as _couleurs de demi-grand feu_, include turquoise (_ts’ui sê_), made from a preparation of old copper (_ku t’ung_) and nitre; bright yellow (_chin huang_), composed of 1⅕ oz. of antimony mixed with 16 oz. of pulverised lead; bright green (_chin lü_), composed of 1⅖ oz. of pulverised copper, 6 oz. of powdered quartz and 16 oz. of pulverised lead; purple (_tzŭ sê_), composed of 1 oz. of cobaltiferous ore of manganese, 6 oz. of powdered quartz and 16 oz. of pulverised lead. These colours, melting as they did at a lower temperature than that required to vitrify the porcelain body, had to be applied to an already fired porcelain “biscuit.”[226]