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All pottery falls into two main
categories: Low fired “earthenware” like Mexican pottery, flower
pots, brightly colored decorative ware and inexpensive dinnerware.
This pottery is fired to temperatures below 2100° F. (Cone 1). This
pottery is not very strong and chips easily. The famous “desert
rose” dinnerware is an example of earthenware dinnerware; it may
be pretty, but it not suitable for daily use.
Stoneware and porcelain* are
“high fired” to temperatures ranging from 2200° F. (cone 5) to 2350° F.
(cone 10). This extremely high temperature produces ware that is
very strong and durable.
English “bone china” and Chinese porcelain are examples of high fired
pottery.
In general, firing to cone 10
or higher requires a fuel fired kiln (natural gas, propane, oil or even
wood) instead of an electric kiln. In addition to achieving the high
temperatures required for stoneware and porcelain, a fuel fired kiln can
produce a “reduction” atmosphere that imparts a range of colors and
surface textures in the clay and glaze that is impossible to achieve with
an electric fired kiln. The disadvantages of this high temperature
firing are the complicated nature of the firing process and the high cost
of fuel.
* Porcelain is a
smooth white clay while stoneware is coarser and is usually tan or brown.
Both are fired to the same temperature and are about equal in strength and
durability.
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