This paper looks at factors affecting electric furnaces making borosilicate glass. During production, phenomena lowering the quality of the glasses often occurs. For example: (a) the yield of glass molten, electric parameters & operation temperature are stable, but the liquid viscidity of glass fluctuates; (b) melted temperature is very high, but unmelted quartz particles in final products can still be present in the glass; (c) steeping dusts & small bubbles are often found in the final products & (d) red roof & turnover roof are often seen in production too. According to experience from two electric melting furnaces & a furnace revised & designed by the authors for borosilicate glasses with the range of thermal expansion coefficients (40x10-7/C~70x10-7C) the theoretical relation between the type of furnace, cold furnace roof, & glass formula, is discussed in this paper.
