Ways Of Eliminating Defects In Borosilicate Glasses

Studies on the occurrence of stone and cord in continuous tank melting of borosilicate glass due to the formation of silica-rich scum in the working end are reported. It is concluded that to obtain good quality high-viscosity borosilicate glass the furnace atmosphere should contain no more than 0.3-0.4 vol % of CO, a neutral pressure should be maintained and the glass composition should include no more than 0.1 wt% of SO3.