Blue and white porcelain is contrived using the color blue, usually from cobalt oxide, to create designs on shaped clean, white clay that is then covered in a layer of transparent glaze and baked in a kiln at high temperatures. Traces of blue and white wares are found beginning in the Tang dynasty (618-907) but it was not until the Yuan dynasty (1271-1368) that the art reached perfection. In the early 14th century, mass-production of fine, transparent, blue and white porcelain started at Jingdezhen (景德鎮), sometimes called the “porcelain capital (瓷都)” of China.