fa904 faince French antique plate, 1800's
The tin glaze used in faience is actually a lead glaze that has been rendered white and opaque by the addition of tin oxide. In the production process, an unglazed article is fired in a kiln and is then dipped in the tin glaze, which is allowed to dry. Designs are then painted on the glaze, which sets them off and preserves them during a second firing at high temperature. The colours used to paint designs were limited to the few that could tolerate high heat until the 18th century, when a low-fire overglaze enamel was used.