Ancient Egyptians made glass beads and jars by winding a thread of glass around a clay core. Syrians invented glass-blowing at the end of the first century BC. To make glass, silica (sand) and potash or soda ash are mixed with limestone carbonate and heated until they fuse into a molten mass. The glass blower gather a glob of molten glass on his pipe and blows through it, swings it, and spins it to create the shape he wants. Additional globs of glass may be added for stems or bases. Final shaping is done by rolling the pipe on a support while shaping the glass with a variety of tools. The piece is removed from the pipe and smoothed. Alternatively, the glassblower may place the pipe into a mold as he blows so that a pattern is imprinted on the glass as it expands.