Lead-glazed earthenware in the context of "Sancai"

Faience or faïence (/faɪˈɑːns, feɪˈ-, -ˈɒ̃s/; French: [fajɑ̃s] ) is the general English language term for fine tin-glazed pottery. The invention of a white pottery glaze suitable for painted decoration, by the addition of an oxide of tin to the slip of a lead glaze, was a major advance in the history of pottery. The invention seems to have been made in Iran or the Middle East before the ninth century. A kiln capable of producing temperatures exceeding 1,000 °C (1,830 °F) was required to achieve this result, after millennia of refined pottery-making traditions. The term is now used for a wide variety of pottery from several parts of the world, including many types of European painted wares, often produced as cheaper versions of porcelain styles.

English generally uses various other terms for well-known sub-types of faience. Italian tin-glazed earthenware, at least the early forms, is called maiolica in English, Dutch wares are called Delftware, and their English equivalents English delftware, leaving "faience" as the normal term in English for French, German, Spanish, Portuguese wares and those of other countries not mentioned (it is also the usual French term, and fayence in German). The name faience is simply the French name for Faenza, in the Romagna near Ravenna, Italy, where a painted majolica ware on a clean, opaque pure-white ground, was produced for export as early as the fifteenth century.

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.

Green-glazed pottery (Chinese: 緑釉陶器) was a type of colored pottery developed in China during the Eastern Han period (25–220 CE). The body of green-glazed pottery ceramics was made of clay, coated with a layer of glaze, and fired at a temperature of 800 degrees Celsius. Green-glazed pottery is a type of lead-glazed earthenware (Chinese: 鉛釉陶器): lead oxide was the principal flux in the glaze, often mixed with quartz in the proportion of 3:1. The polychrome effect was obtained by using as coloring agent copper (which turns green).

Due to the low firing temperature, the bodies are earthenware, and the glaze often only applied to parts of the objects, which are fragile and have high water absorption. In some cases the lead glazes make the objects slightly poisonous. For these reasons, the objects are only known as grave goods from burials, and examples used in everyday life have not been found. In surviving examples the glaze has often corroded, and turned a "greyish-silver". They are liable to flake off.