In the Roman period from about 30 BC to about AD 359, Wadi el-Natrun was probably one of the main centers of the glass industry in Egypt. In this district, the essential materials for glass-making processes, mainly silica and natron, were and are still quite abundant. Two kinds of crucibles were in use: fritting and melting. The first kind was used for fritting the raw materials of glass to produce glass frit blocks. Such fritting crucibles had a rectangular form which is not usually encountered in other places. Probably this was intended to facilitate the transport of the glass frit blocks produced to glass factories in different places where raw materials were not available. Dimensions for two fritting crucibles are proposed. The body texture is coarse, highly porous and almost loose. These features were intended by the ancient glassmaker to release the frit block easily by fracturing the crucible, which was thus used only once. The chemical composition is distinguished by a high content of iron oxide, lime, magnesia and alkalis, thus decreasing the resistance of the crucible to corrosion. The mineralogical composition is mainly: alpha quartz albite, oligoclase, andesine, diopside, augite and a small amountof anorthoclase and other trace minerals. The crucible material has been found to have been originally made by mixing mud with sand to which an amount of chopped straw was added; after sun-drying the crucible was baked before use. The temperature employed in this process never exceeded 1100°C since, under prolonged heating, the crucible material fuses in the range 1150-1200°C.