CHINA
Generally the matter used for painting blue porcelain is cobaltiferous manganese. It is found at no great distance below the surface of the ground, the excavators not being obliged to dig to a depth of more than one mètre at most. It occurs in all the provinces of the empire and there are three grades of it. Before use it has to be baked to red heat in a mass of clay. From each pound of mineral thus treated, barely seven ounces are obtained. Blue of the first quality is always used for the decoration of very fine porcelains, or on pieces destined for the palace, with dragon and phoenix designs. Thus 36 dollars must be spent to obtain thirteen litres of first-class blue; one-half of that sum for a similar quantity of second-class mineral, and one-seventh of it for the third-class variety. All the best blue used at Ching-tê-chên is found in the province of Chê-kiang. That found elsewhere is inferior. After the mineral has been roasted it is ground very fine in a mortar of unglazed porcelain, and afterwards moistened with water. When painted on the surface of the ware it is black, but becomes blue by exposure to the heat of the furnace.
It will be observed that in these extracts no mention is made of the Hui-ching, or Mohammedan blue. This choice mineral ceased, apparently, to be procurable after the Chia-ching era (1522—1566). The Kang-hsi potters and their successors used the native mineral only, but used it in such a manner as to obtain a colour little, if at all, inferior to that of the choicest Ming specimens. Many other details on the subject of cobalt are given in the Tao-lu, but they embody little information and are grouped in a confused manner. The substance of what they convey is that blue of the choicest quality was scarce, expensive, and difficult to prepare. Even when the best mineral was employed, any slight excess of temperature in the porcelain kiln sufficed to burn out its tint. There was, however, a particular variety capable of
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