Tin-glazing is the process of giving tin-glazed pottery items a ceramic glaze that is white, glossy and opaque, which is normally applied to red or buff earthenware. Tin-glaze is plain lead glaze with a small amount of tin oxide added. The opacity and whiteness of tin glaze encourage its frequent decoration. Historically this has mostly been done before the single firing, when the colours blend into the glaze, but since the 17th century also using overglaze enamels, with a light second firing, allowing a wider range of colours. Majolica, maiolica, delftware and faience are among the terms used for common types of tin-glazed pottery.
An alternative is lead-glazing, where the basic glaze is transparent; some types of pottery use both. However, when pieces are glazed only with lead, the glaze becomes fluid during firing, and may run or pool. Colours painted on the glaze may also run or blur. Tin-glazing avoids these problems.
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