The basic process for producing silicon has remained unchanged for decades: quartz or gravel (SiO2) is blended with a carbon source and superheated in a submerged arc furnace. As the mix heats, the carbon reacts with the oxygen in the quartz and forms CO gas, thereby reducing the quartz to 99% silicon in molten form. Next, the liquid silicon is drained, or tapped, from the bottom of the furnace. Although the heating/reduction process is continuous while the furnace is in operation, raw materials are added to the furnace and silicon is tapped from the furnace in batches.