How porcelain is made

Porcelain is fired so hot that part of the clay turns to glass, which is why light shines through a thin cup.

stations: 6
things upstream: 18
raw sources: 11
steps from the ground: 5

The short version

Porcelain is made from kaolin blended with quartz and feldspar, shaped, then fired in a kiln at 1,200 to 1,400 °C. At that heat the body vitrifies and grows crystals of the mineral mullite. That gives the ware its strength, its whiteness and its translucence.

Blend the porcelain body

Kaolin is the key clay, though clay minerals may be only a small part of the whole. Formulations combine kaolin with quartz and feldspar. English bone china traditionally used two parts bone ash, one part kaolin and one part china stone.

Goes in
Kaolin Quartz Feldspar
Shape the ware

Porcelain is formed by throwing, by slip casting in plaster molds, or by pressing. It is harder to work than earthenware because the paste has less natural plasticity.
Fire the biscuit

Modern porcelains are biscuit-fired at around 1,000 °C. The first firing firms the ware enough to be handled and dipped in glaze.

around 1,000 °C
Dip it in glaze

Porcelain needs no glaze to be watertight, because the body is already vitrified. Glaze mostly adds decoration and resistance to dirt and staining.
Fire it hot to vitrify

The glaze firing goes to about 1,300 °C or greater. The body vitrifies and grows interlocking needles of mullite, which gives the strength and the translucence.

1,200–1,400 °C
Decorate with enamels

Delicate pigments go on over the glaze as overglaze enamels, then ware is fired again at a lower heat so they do not burn off.

Goes in
Pigment

End of the linePorcelain Next it goes into snow globe.

Worth repeating

The Meissen factory made the first European porcelain, and its kiln reached up to 1,400 °C.
The word porcelain comes from the old Italian porcellana, which means cowrie shell.
Song dynasty dragon kilns could fire as many as 25,000 pieces at a time.