How it began
İznik is a town in Anatolia that had long made simple earthenware with painted decoration under the glaze. In the last quarter of the fifteenth century its craftsmen began to make pottery of a much higher quality, with a fritware body painted in cobalt blue under a colorless lead glaze. The earliest surviving pieces are thought to date from around 1480. No written record explains how the change came about, but the designs were clearly influenced by the Ottoman court in Istanbul. The aim was to match the prestige of Chinese porcelain.
Before it existed
Fritware itself was not new. It had been made in the Near East since the thirteenth century, and the Iranian town of Kashan was an important center. In 1301 Abu'l-Qasim of Kashan wrote down a recipe of ten parts silica to one part glass frit and one part clay. The Kashan frit was made from powdered quartz and soda. What İznik achieved was a white surface, which the sources call a major innovation, and a manufacturing process thought to be an invention of Anatolian potters.
How it works
The body is quartz sand mixed with a little finely ground glass and some clay. In the kiln the glass melts and binds the rest. İznik potters added lead oxide to the frit along with quartz and soda. The paste was stiff, so vessels were built in sections and joined, and dishes were shaped over a mold on the wheel. The body was coated with a thin white slip of the same ingredients, more finely ground and free of iron. It was then painted, glazed and fired at about 900 degrees Celsius, probably in protective cases called saggars.
How it spread
At first only cobalt blue was used. Turquoise was added from about 1520, and a bright red slip rich in iron oxide, laid thickly under the glaze, appeared around 1560. From the middle of the sixteenth century the potters turned out large quantities of tiles for the imperial buildings designed by the architect Mimar Sinan. Production continued until the end of the seventeenth century.
What lasted
The wares are technologically distinct from the Iranian pottery of the same period and from other Ottoman tilework. Pieces are held in major collections, among them the British Museum and the Art Institute of Chicago, and the tiles remain in place on Ottoman buildings. The University of Kansas notes that the underglaze technique that arose at İznik in the fifteenth century changed the standing of the town as a center of production.
