Clay: Encyclopedia II - Clay - Historical and modern uses of clay

Clay - Historical and modern uses of clay

Clays are heavy in texture yet soft to the touch. Clay is a malleable substance when wet, which means it can be shaped easily with the hands. When dry, it becomes firm and when "fired," or hardened by intense heat, clay becomes permanently solid. A fireplace or oven specifically designed for hardening clay is called a kiln. These properties make clay an ideal substance for making durable pottery items, both practical and decorative, with different types of clay and firing conditions giving earthenware, stoneware and porcelain. Early humans discovered the useful properties of clay in prehistoric times, and one of the earliest artifacts ever uncovered is a drinking vessel made of sun-dried clay. Depending on the content of the soil, clay can appear in various colors, from a dull gray to a deep orange-red.

Clays sintered in fire were the first ceramic, and remain one of the cheapest to produce and most widely used materials even in the present day. Bricks, cooking pots, art objects, dishware, spark plug bodies, and even musical instruments such as the ocarina are all made with clay. Clay is also used in many industrial processes, such as paper making, concrete production, and chemical filtering.

Adapted from the Wikipedia article "Historical and modern uses of clay", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki