Painting in blue and black under the glaze was a technique developed round about 1200 AD in Iran. The immediate precursor of the techniques seems to have been painting in black slip under a clear or transparent turquoise glaze, the so-called ‘silhouette ware’ (see no.9 [
EA1956.130]). The thickness of the slip and the carving technique employed in the latter wares lent itself to broad, boldly-conceived designs, but was unsuitable for more precise painting and for all the sorts of designs which were becoming more popular in illustrated manuscripts. In order to meet this challenge the potters first developed underglaze-painting, and later overglaze painting (see nos. 13-14 [EAX.1302 &
EA1956.36]). In underglaze-painting the blue derives from cobalt oxide, and the black from a mineral containing iron, manganese and chrome mined near Kashan in western Iran. The important discovery of the potters was that both these pigments are relatively stable under an alkaline glaze.
The design on this bowl shows the way the blue and black were normally used, the blue for broader bands, the black for detailed work. Here the central motif is the face of the Sun. Medieval Islamic society took astrology very seriously, and numerous objects were decorated with the Sun and other planets, or with the signs of the zodiac (see no. 16 [
EA1956.58]). In contemporary metalwork, where more elaborate designs were laboriously worked out in silver and copper inlays, the Sun is normally surrounded by the other six known planets, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn. In ceramics the tendency in decorating was always towards a shorthand, and here the Sun is probably meant to bring to mind the whole of the heavens and the good fortune which might thereby accrue to the owner of the bowl.