In casting we start with a wax model. On this wax model we shape the glass mold. The glass mold is made from a mixture of plaster and quartz. When the mold is cured, the wax model is melted out of the mold with steam. After drying the mold is ready to use.
In an open or closed mold, we melt chunks of glass or grinded glass. With an open mold the glass is stacked directly into the mold and during the heating in the oven glass flows out. With a closed mold the glass is stacked in a container (a plaster funnel or flowerpot), which is placed above an opening in the mold. During the heating glass flows into the mold through a hole in the bottom of the container.