There have been many ways of CZECH glass bead making. The earliest was to wind molten glass around a form and allow it to set and cool, creating round beads. The glass can also be blown into a form or mold, creating hollow shapes in the beads which are lighter than wound ones. Then pressed glass molds were developed in Bohemia, producing a product that is more durable and robust than earlier methods. Later this process became automated by hydraulic bead presses which could turn out thousands of identical beads quickly. The presses used a combination of high pressure and heat caused by that pressure to convert powdered glass into glass beads. After the beads were formed they were pierced using high speed drills to create uniform holes. Pressed glass beads are denser than other types.