Stoneware pottery is made from the baking of silicate-based materials. Porcelain is actually a special kind of stoneware formed when admixtures of kaolin clay and feldspar are isolated to 95 percent purification and then baked at extremely high temperatures--usually, around 1,300 degrees Celsius. Earthenware is a kind of stoneware that contains more impurities and allows liquids to seep through.

Creating stoneware from natural clay requires what is known as a kiln, or a high temperature oven. After kiln-firing, stoneware tends to be rather nonporous. Earthenware, the lower grade of stoneware, still absorbs 10 percent of moisture that comes into contact with it. Slightly purer earthenware absorbs five percent of moisture, while porcelain absorbs only thee percent.

The darker clays used in the making of stoneware may impart interesting, exotic properties. Iron oxides and other heavy-metal byproducts contained in clays make earthenware more susceptible to certain kinds of environmental degradation, like rusting. That being said, these so-called impurities may also impart stronger mechanical properties to the ceramics.

Stoneware artifacts can be found from ancient times. Indeed, one of the techniques by which anthropologists evaluate ancient civilizations is to examine their facility with earthenware. In modern times, pottery artists have developed ever more intricate ways to manipulate the chemistry of stoneware. For instance, innovator Josiah Spode developed a process to create Fine Bone China, a particularly resilient and beautiful kind of stoneware.