Throughout the East a type of white pottery was made which, though stimulated by the Chinese example, may have been a relic of the knowledge of the Egyptians. A crude clay was coated with a white preparation, possibly ground quartz, and upon this there were painted conventional designs in sombre colors. A clear glaze covered the whole and imparted to the colors a beautiful quality as of pebbles under water. The nature of the glaze is made evident by the hues assumed by the metallic oxides employed as colorants. Copper oxide affords a turquoise blue, manganese, a wine purple, and iron, a brick red. If the glaze had contained any considerable amount of lead oxide, these colors would have been quite different; copper would have produced green, manganese, dark brown, and iron, yellowish brown. The iron pigment was evidently a clay, sometimes spoken of as Armenian bole. The red color is always in raised masses because if a thin wash had been used the color would have yielded to the action of the glaze.
This ware, commonly called Oriental _engobe_ ware, affords a fruitful study. Effects similar in character were produced by the late Theodore Deck of Paris, but no considerable use of the ancient methods has ever been attempted.
The use of tin and lead in glazing was known to the Arabian and Moorish potters but these ingredients were not abundant in the East. When, however, the Moorish hosts conquered a part of Spain in the twelfth century it was found that both lead and tin were available. The result was the development of the enameled ware known by the generic name Maiolica. Some have maintained that this was first made in Italy but the name is derived from the island of Maiorca from which much of the pottery was exported. The famous Alhambra vase remains as a monument to the skill of the Hispano-Moresque craftsmen, but it was the Italian artists of the Renaissance who brought the enameled wares to perfection. The interest here is artistic and technical rather than historical, but no one can study the work of the period without learning something of Luca della Robbia and Giorgio Andreoli, of Gubbio and Pesaro and Castel Durante.
The use of lead in the glaze proved seductive. It simplified the technical problems and provided a brilliant surface but alas! the colors suffered and one by one they succumbed. The blue of cobalt, however, proved indestructible and so, when the technical knowledge of the South met the traditions borrowed from the Chinese, there was born, in the little town of Delft in Holland, the blue enameled ware which has ever since been known by the name of its native place.