Earthenware teapot, Japanese, 18th century.
© Science Museum / Science & Society Picture Library
Earthenware is the earliest known type of pottery and is still made today. Earthenware is relatively coarse and porous, so it is usually glazed. There are two main types of glaze; a transparent lead glaze, which is applied over the decoration and an opaque tin glaze, which is applied with a built-in decoration.