Mosaic wares originated with the introduction of glass molding in the Hellenistic world around 220 B.C. when Greek glassworkers adapted the then new potter's technique for mold-shaped bowls. In mold casting, a hot disc of glass is slumped over a conical-shaped clay mold and pressed down so as to create a smooth rim. The glass, while still hot, is then removed from the mold to prevent cracking and breaking. The first cast vessels had a monochrome repertoire: aquablue, light green, amber, purple, and white. By the late 2nd century B.C., however, a brand new style of riotously colored glassware emerged known as mosaic wares. The Romans of the late Republican era took mosaic wares, improved their technology, and greatly increased the diversity of their color palette.