A system and a method for producing silicon from a SiO2-containing material that includes solid SiO2. The method uses a reaction vessel including a first section and a second section in fluid communication with said first section. The method includes: heating the SiO2-containing material that includes the solid SiO2 to a SiO2-containing material that includes liquid SiO2, at a sufficient temperature to convert the solid SiO2 into the liquid SiO2; converting, in the first section, the liquid SiO2 into gaseous SiO2 that flows to the second section by reducing the pressure in the reaction vessel to a subatmospheric pressure; and reducing, in the second section, the gaseous SiO2 into liquid silicon using a reducing gas. The reducing of the pressure is performed over a continuous range of interim pressure(s) sufficient to evaporate contaminants from the SiO2-containing material, and removing by vacuum, the one or more evaporated gaseous contaminants.