Tin-glazing

Tin-glazing is the process of giving ceramic items a tin-based glaze that is white, glossy and opaque, which is normally applied to red or buff earthenware. The opacity and whiteness of tin glaze encourage its frequent decoration with colour.

Tin oxide is valued in glazes as both an opacifier and as a white colorant. Tin oxide has long been used to produce a white, opaque and glossy glaze. As well as an opacifying agent, tin oxide also finds use as a colour stabiliser in some pigments and glazes. Minor quantities are also used in the conducting phases in some electrical porcelain glazes.

The earliest tin-glazed pottery appears to have been made in Abbasid, Iraq (750-1258 AD)/Mesopotamia in the 8th century, fragments having been excavated during the First World War from the palace of Samarra about fifty miles north of Baghdad. From Mesopotamia, tin glazes spread to Islamic Egypt (868–905 AD) during the 10th century, and then to Andalusian Spain (711-1492 AD), leading to the maximum development of Islamic lusterware.

The history of tin glazes in the Islamic world is disputed. One possible reason for the earlier production of tin-glazed wares could be attributed to the trade between the Abbasid Empire and ancient China from the 8th to 9th century onwards, resulting in imitation of white Chinese stoneware by local Islamic potters. Another might be local glaze-making rather than foreign influence, supported by the similarility between the chemical and microstructural features of pre-Islamic white opaque glazes and that on the first tin-opacified wares

From the Middle East, tin-glaze spread through the Islamic world to Spain. In the 13th century, tin glazes reached Italy, where the earliest recorded reference to their use is in the 1330s, resulting in the emergence of Italian Maiolica. Amongst others, Luca della Robbia, born in Florence circa 1400, used tin oxide as an opacifier in glazes. Potters began to draw polychrome paintings on the white opaque surface with metallic oxides such as cobalt oxide and to produce lustreware. The off-white fired body of Delftware and English majolica was made to appear white, and hence mimic the appearance of Chinese porcelain, by the application of a glaze opacified and coloured white by the addition of tin oxide.

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Wikipedia