1560. The red slip containing iron oxide was applied in a thick layer under the glaze. Even after the introduction of a range of different pigments, vessels were sometimes still produced with a restricted palette. The wares were glazed with a lead-alkaline-tin glaze, whose composition has been found from analysis to be lead oxide 25-30 percent, silica 45–55 percent, sodium oxide 8–14 percent and tin oxide 4–7 percent. Tin oxide is often employed to render glaze opaque but in İznik glazes it remains in solution and is transparent. Abū'l-Qāsim described the use of earthenware saggars with a fitting lid. Although Miletus ware bowls were stacked in the kiln one on top of the other separated by spurs, the lack of spur marks on Iznik fritware suggests that saggars were used. Firing was done in an updraft kiln, to about 900 °C. Blue-and-white ware (1480–1520) In the final decades of the 15th century, potters in Iznik began producing blue-and-white fritware ceramics with designs that were clearly influenced by the Ottoman court in Istanbul. There are no surviving written documents that provide details on how this came about. The earliest specific mention of Iznik pottery is in the accounts for the Imperial kitchens of the Tokapi palace for 1489–1490 where the purchase of 97 vessels is recorded. The earliest datable objects are blue-and-white border tiles that decorate the mausoleum (türbe) in Bursa of Şehzade Mahmud, one of the sons of Bayezid II, who died in 1506–1507. The term 'Abraham of Kütahya ware' has been applied to all the early blue-and-white Iznik pottery as the 'Abraham of Kütahya' ewer, dating from 1510, is the only documented vessel. The art historian Julian Raby has argued that the term is misleading as the ewer is atypical and has instead proposed the term 'Baba Nakkaş ware' after the name of the leading designer attached to the Imperial court in Istanbul. The earliest surviving Iznik fritware objects, dating from probably around 1480, are believed to be a group of vessels painted in a dark cobalt blue in which much of the dense decoration is in white on a blue background. The vessels have separate areas of Ottoman arabesque and Chinese floral designs. The combination of these two styles is referred to as Rumi-Hatayi where Rumi denotes the Ottoman arabesque patterns and Hatayi the Chinese inspired floral patterns. Many of the meticulously painted arabesque motifs of this early