Blue and White porcelain in China came about as a result of the combination of the Chinese porcelain tradition with the trade in cobalt blue from Persia. Porcelain is a hard white ceramic composed of white-china clay, called kaolin, and refined porcelain stone, or petuntse. When fired together, these materials fuse to create a hard, vitrified ceramic. Blue and White porcelain is the successor to the Chinese Qingbai and Shufu traditions that preceded it, or ceramics with a white glaze and a slightly blue or blue-green tint. To achieve the Blue and White decorative style, cobalt underglaze is applied to the porcelain; it is then covered in clear glaze and fired. Cobalt was used by Persian potters for centuries before its import to China. It was introduced in approximately 1325 A.D. through with Persian merchant communities established along the Chinese coast. Following the introduction of this new, exotic decorative style, the city of Jingdezhen, known as the porcelain capital of China, began producing Blue and White porcelain wares with imported cobalt. The hold of the Ming [Ming] emperors gradually weakened in the first decades of the 17th century; this eventually led to the collapse of that dynasty and the creation of a new one, the Qing [Ch'ing], by the foreign-born Manchus. At the porcelain manufacturing center of Jingdezhen [Ching-te Chen], the decline of the empire meant opportunity in the form of newly opening foreign markets. Internal economic difficulties brought men with a broader knowledge of Chinese painting than had hitherto been the case, and the result was the production of a series of vessels, like this one, of unprecedented ambitiousness. On the body of the vase are a dragon and a tiger, on the neck, the unicorn (Qilin [Ch'i-lin]) and phoenix. The whites have a positive value; more than that, they are also pictorial, actually standing for the mists that hover in front of waterfalls. The relationship between neck and body is worked out in terms of white and blue areas; but the two parts compete for attention, and there is no ordinary hierarchy. A sophisticated, playful hand is at work, as is also suggested by the blurred edges- reminiscent of wet ink on paper- of the cloud around the dragon's head. If the tortoise had been shown rather than the tiger, the four creatures on this vase would constitute the "four miraculous creatures": one scaly, one shelled, one furry, and one feathered. Probably "yin" and "yang" polarities are more important here; the moist dragon is opposed to the dry tiger, and a male phoenix is paired with a female unicorn. Together they may allude to the ancient notion that the appearance of these creatures on earth is a sign of the rule of a just king. In the middle years of the 17th century, that would have been more of a hope than a reality.