Jasperware
The formula for Jasper, a dense white stoneware, was Josiah Wedgwood’s most closely guarded secret. For the chemically-inclined, we know that it contains one part calcined flint, three parts purbeck clay, one quarter part fired and washed alabaster, and six parts sulfate of barium, all fired at about 1200-1250 degrees centigrade. When thinly potted and fired at slightly higher temperatures, Jasper becomes translucent and rings like porcelain.
“Invented” by Wedgwood after many trials, Jasperware came to be produced in at least 21 colors, with some colors such as blue, having at least five different shade variants. It is either solid in color all the way through, or dipped (color outside, white inside). It is capable of being thrown, molded, engine-turned, ornamented, laminated, lapidary-polished and glazed. Jasperware has been in continuous production since 1774 and has been used to make every shape and form in the company’s inventory. It is considered the most important contribution to the ceramic art since the Chinese invention of porcelain nearly 1,000 years earlier.