simple thing about clay (泥土的簡介)
earthenware clay (低溫土)
* red earthenware or terra-cotta is a natural clay,
it is high in iron so it got a rich rusty colour,
firing range: 1,000 - 1,180 °C
stoneware
clay (高溫土)
* which is harder and stronger than earthenware when fired.
If the particles of the clay is fused and vitrified,
the pot is non-porous even unglazed.
Glaze is an extra material for hygienic or decorative purposes.
firing range: 1,200 - 1,300 °C
porcelain (瓷土)
* the whitest & purest clay body, which is capable of very high temp firing.
When pots are made very thin,
the fired clay itself is quite translucent while hard and nonporous.
firing range: 1,300 - 1,350 °C