What Is Porcelain? As defined by United States Customs in the Harmonized Tariff Schedule Paragraph 69 for US import purposes
6909 through 6914
(a) The terms "porcelain,""china" and"chinaware"embrace ceramic ware (other than stoneware), whether or not glazed or decorated, having a fired white body (unless artificially colored) which will not absorb more than 0.5 percent of its weight of water and is translucent in thicknesses of several millimeters. The term"stoneware" as used in this note, embraces ceramic ware which contains clay as an essential ingredient, is not commonly white, will absorb not more than 3 percent of its weight of water, and is naturally opaque (except in very thin pieces) even when absorption is less than 0.1 percent.
(b) The term "bone chinaware" embraces chinaware or porcelain the body of which contains 25 percent or more of calcined bone or tricalcium phosphate.
(c) The term "earthenware" embraces ceramic ware, whether or not glazed or decorated, having a fired body which contains clay as an essential ingredient, and will absorb more than 3 percent of its weight of water.
(d) The water absorption of a ceramic body shall be determined by ASTM test method designated C373 (except that test specimens may have a minimum weight of 10 g, and may have one large surface glazed).