How ceramics are made

Firing runs from 600 °C to 1,400 °C, and the heat decides whether clay stays porous or turns glassy.

stations: 6
things upstream: 4
raw sources: 4
step from the ground: 1

The short version

A ceramic is a shaped mineral body, usually clay, that is hardened by firing. Makers blend clay, silica and feldspar into a body, form it by hand, press or mold, dry it, and fire it once. Glazed ware gets a coat of glass-forming powder and a second firing that melts it into a smooth skin.

Blend the clay body

A body is a recipe of clays, kaolin, feldspar and quartz, and the recipe sets how hot the ware can be fired. Prepared bodies are by far the dominant type used in industry.

Goes in
Clay Kaolin Feldspar Quartz
Form the shape

Potters throw clay on a wheel. Factories press damp granulated powder in a mold, shape the plastic clay against a spinning plaster mold, or pour liquid clay into a plaster mold.
Dry to bone-dry

At the leather-hard stage the clay holds about 15% moisture and can still be trimmed. Bone-dry clay has almost no moisture left and is extremely brittle, so it is ready for the kiln.
Fire the first time

The bisque firing changes the minerals in the clay permanently. As a rough guide, earthenware is fired at 1,000–1,200 °C, stoneware at 1,100–1,300 °C and porcelain at 1,200–1,400 °C.

600–1,400 °C across all types
Glaze the ware

A glaze is a coating that melts into glass. It is applied to the biscuit ware by dipping or spraying. Glaze lowers porosity and gives a smooth, colored surface.
Fire again to melt the glaze

The glost firing melts the glaze so it bonds to the body. Depending on the temperature schedule, it may also mature the body further.

End of the lineCeramic Next it goes into hip implant, faucet, turbine blade.

Worth repeating

People have been making ceramics for at least 26,000 years, and the earliest known pieces found so far were sculpted figures, not dishes.
In the 1960s, General Electric scientists found that aluminum oxide could be made translucent under the right manufacturing conditions.
The word ceramic comes from the Ancient Greek keramikos, meaning of or for pottery.