What it is made of

This lesson asks you to identify the factors that decide whether a material suits a product or a structure. The museum offers one record on glazed ceramics, an opaque white glaze made with tin oxide in ninth-century Iraq. It shows what makers chose; the tests of strength, cost and weather are for your class. ¹

List what the maker wanted it to do and what the material had to do in use. Then say which of your points the record supports.

Arthur Lane holds, as the record on his book reports, that the Baghdad potters devised the opaque white tin glaze to imitate white Chinese ware and then painted on it ^{2 3}. The record on Abbasid tin-glazed ware says the surface of Chinese porcelain could not be reproduced with a clear lead glaze over white slip, so the potters of Iraq used a device known earlier to the Egyptians: they mixed tin oxide into a modified lead glaze, making it opaque and white ². They then painted on the white surface with cobalt blue, copper green, manganese purple and sometimes antimony yellow, paint and glaze being fixed in one firing ².

On a well-purified yellow or pinkish clay, the tin glaze looked deceptively like porcelain ². The record nevertheless calls what was made in Iraq an imitation: imitations of the white porcelain were found at Samarra alongside the Chinese originals ².

The record says the tin glaze made a clay body look deceptively like porcelain ². For a bowl used every day, is that appearance enough to judge the material, and what else would you want to test, and why?

• Abbasid tin-glazed ware: how the white glaze was made and which colours were painted on it.
• Islamic lustreware: pottery with a metallic sheen, and how Lane describes its making.
• Early Islamic Pottery: Lane's book and what it says about the Baghdad potters.
• Arthur Lane: the historian on whom this record rests.

Read about Abbasid tin-glazed ware. Write what the maker wanted, what was added to get it, and one question about how long it would last.