All ceramics, including tableware, are earthenware, stoneware or porcelain. Within the porcelain category, there is hard-paste, soft-paste and bone china. Distinguishable by its bright white color, translucency and strength, bone china is the most celebrated and the most expensive form of fine porcelain.
Porcelain dates back to the Shang Dynasty in China (16th to 11th century B.C.), but it wasn't until the Han Dynasty (206 B.C. to 200 A.D.) that it made its way to England. There, potters embraced the art form, calling it "china" due to its place of origin.
Three Types of Porcelain
Hard-paste china comprises china clay (also called "kaolin": a soft, white clay first mined from the Kao-ling hills in Guangxi, China), petuntse (a feldspathic rock ground down and mixed with the china clay) and flint. Fired at very high temperatures (up to 1,400 C or 2,552 F), the finished product typically has a gray or blue tint and chips easily. Soft-paste porcelain, made from china clay and petuntse as well as "frit," a ground glass-like material, fires at lower temperatures (1,100 C or 2,015 F), and is fragile and porous, making it unsuitable for holding liquids. Bone china comprises bone ash, petuntse and china clay. Fired at the same high temperatures as hard-paste china, it is strong, chip-resistant, completely waterproof and typically bright white in color.
Bone China’s History
The English pottery company Spode made an important advancement to china in the late 18th century. Established by Josiah Spode I, the company initially turned out reproductions of Chinese pottery as well as original works. Josiah Spode II, who took over the family business in the late 1700s, was determined to create a stronger, brighter china. Experimenting with calcified cattle bones, he discovered that he could create a pure white color and strengthen the porcelain so that the finished material could be quite thin—delicate and translucent—while still resisting chips and breaks. Other English potters quickly embraced the use of bone ash in china.
The formula Spode developed, used by English potters to this day, is roughly six parts bone ash, four parts petuntse and three and one-half parts china clay. The bone ash does come from bones, typically from animals processed for dog food. Cleaned of all remaining meat and glue, the bones are heated to 1000 C (1832 F--just a bit hotter than crematoriums) and ground into ash to be mixed with the petuntse and clay.
The Expense of Bone China
Acquiring the materials for bone china is more costly than those used for most hard-paste and soft-paste porcelain. In addition, the potteries which produce it decorate their pieces with enamels and other printing materials, adding to both the design and production costs. Well-established, centuries-old potteries, such as Spode and Wedgewood, built their reputations on quality and design. Collectors appreciate the traits that can be found solely with bone china: beautifully designed, translucent and delicate, yet strong enough to be practical for fine dining or other uses. Bone china is a luxury and is priced accordingly