The Western world’s awareness of China has, throughout most of history, centred on two export commodities: the Romans knew China as Serica, the place from which silk came, while for Europeans of more recent centuries the country was synonymous with the porcelain it produced. China began to export pottery on a large scale not much before the Tang dynasty (ad 618-907), a date secured by the vast deposits of sherds at sites such as Fustat (Old Cairo), but the qualities that made Tang stonewares sought-after rested on the technical achievements of a long ceramic tradition notable for its sophistication even in Neolithic times. Painted pots of the Yangshao Neolithic were fired at temperatures sometimes exceeding 1000°C; unpainted Longshan pots fired under reducing conditions show expert control of kiln atmospheres as well as occasional use of the potter’s wheel. Glazed stonewares appeared in Shang times, shortly after the middle of the 2nd millennium bc (see Wucheng), and kaolin, an important ingredient of later porcelains, was used to make the Shang white pottery. The glaze of the Shang stonewares and their Zhou descendants (see Tunxi) was high-fired and leadless. Lead-glazed earthenwares came into use just before the Han dynasty, later enjoying a special vogue in the gaudy ‘three-colour’ pots and figurines of the Tang period. Stonewares with high-fired leadless glazes continued to be made, however, the gradual perfection of these wares being associated with the Yue region in the southeast. Growing experience with white-bodied stonewares led eventually to the production of true porcelain around the 9th century ad. The term ‘porcelain’ is generally reserved for a vitrified ceramic material prized for its extremely hard white body; it can be so thin as to be translucent and to make a ringing tone when struck. The main constituent of Chinese porcelain is porcelain stone, which occurs in large deposits in several places in China, notably at Jingdezhen in Jiangxi province. Porcelain stone consists chiefly of sericite, hydromica, and quartz (and differs in composition from European porcelain stones); after crushing, washing, and precipitation it is plastic enough to be thrown, and on firing above 1200°C it becomes porcelain. In the Song period the yingqing porcelains of Jingdezhen and the Longquan celadons of Zhejiang province were made of porcelain stone. From the 14th century kaolin was added, as the mixture of kaolin and porcelain stone gives a higher degree of vitrification and a stronger body. Glazes that fire at the same high temperature as the porcelain body are by and large limited to the soft muted colours for which Song porcelains are noted. Early in the 14th century, however, it was discovered that cobalt can give an intense blue to such glazes; this discovery was exploited in the immensely popular blue and white ware, blue decoration being applied to the white porcelain body and covered with a colourless or very pale bluish glaze. Polychrome effects, in vogue from the 15th century onwards, were achieved by applying enamels over the glaze; overglaze enamels include the famille rose and famille verte wares of the Qing period. The unmatched technical quality of Chinese porcelain caused it to be imported and imitated in Korea, Japan, Southeast Asia and the Philippines, India, throughout the Moslem world, and in Europe from the time of the Crusades (seeSinan). Unable to duplicate the hard porcelain body, potters from Iran to Delft copied the outward appearance of Chinese blue-and-white, whose decoration might be said to have enjoyed a worldwide influence out of all proportion to its intrinsic merit. The extent of the trade in Chinese porcelain can be suggested by a single statistic derived from the records of the Swedish East India Company, one of the smaller European companies engaged in the China trade: between 1766 and 1786, when the population of Sweden was about 2 million, more than 20 million pieces of Chinese porcelain were imported into Sweden alone. The imperial kilns at Jingdezhen, which supplied this enormous trade, were described in letters written from China by the Jesuit Pere d’Entrecolles in 1712 and 1722. At about the same time European experimenters managed to produce ceramic materials that fire at temperatures in the same range as porcelain, and factories at Meissen and elsewhere began to manufacture European porcelains not as a rule identical to Chinese porcelain in composition, but able to compete with it.