“The Chinese call any high-fired clay body that makes a clear ringing sound when it is struck ci (tz’u) or porcelain. In the West, a body is considered true porcelain if, in addition tot these criteria, it is white and translucent. Porcelain is made of kaolin (white china clay), feldspar, and silica. Kaolin is named for the hill of Gaoling (Kaoling), which lies to the north of Jingdezhen (Ching-te-Chen). Kaolin is 40 percent alumina, 46 percent silica, and 14 percent water. It is highly refractory and pure white. Petuntse (china stone or literally, “small white rocks”) is a naturally occurring white, feldspathic powdery rock that occurs in China. It was added to kaolin to make porcelain. In the fires of a very hot kiln, petuntse melts and surrounds the refractory particles of kaolin, giving the body strength and making it smooth, almost glassy. Porcelain is fired to 2,280–2,370°F.”

—Suzanne Stauback, from Clay: The History and Evolution of Humankind’s Relationship with Earth’s Most Primal Element, 2005.