MANUFACTURING SHEET GLASS

Method making glass sheet by vertical drawing such that the pit below the glass being drawn is supplied continuously with a direct flow of molten glass, site being provided at which heat is supplied beneath the glass surface in the confines of the pit to create a thermal bearier formed by a current of ascending molten glass so that the molten glass present below the barrier is practically prevented by that part of the wall from passing under the barrier. The speed of drawing the glass may be increased without increasing the risk of corrosion and erosion of the refractory while producing glass free of ripples and similar imperfections.