Clarification of type E alkali-free glass (production of glass beads and continuous glass fiber) with sodium sulfate was investigated in comparison to antimonous anhydride and cerium dioxide. The high effectiveness of sulfate clarification was demonstrated and the process parameters for using it were determined.Glass fibers and materials made from them are widely used for reinforcing polymer and ceramic matrices due to the simplicity of manufacture, low cost, and acceptable physicochemical properties. The fibers are made from glass of different compositions, and type E glass is most in demand throughout the world; it contains (% 2 ): 53 -57 SiO 2 , 5 -8 B 2 O 3 , 13 -15 Al 2 O 3 , 0.5 -2.5 MgO, 20 -26 CaO, 0.2 -0.8 R 2 O, 0.45 -0.6 Fe 2 O 3 , 0 -0.6 F [1] and has high dielectric indexes, mechanical strength, and chemical stability.E glass initially contained no boron oxide. Considering its wide use for production of reinforcing elements for plastics and concretes (complex filaments, rovings, mesh, fabrics), the composition was developed as cheap and accessible. The batch was based on natural materials: sand, clay (kaolin), chalk (lime), dolomite. Later B 2 O 3 , which is a good flux and at the same time improves the strength and dielectric properties of the glass, was added to the composition to decrease the founding and formation temperature [2]. It is most rational to add 5 -8% B 2 O 3 . In this case, its positive effect on the process and performance properties of the glass is maximum, while the volatility is relatively low during founding (in gas-flame furnaces, it does not exceed 8%, versus 15% at high concentrations of boron oxide).The coefficients of the Vogel -Flucher -Tamman (VFT) equation for the temperature dependence were determined with the known values of the temperature characteristics (formation, Littleton, and glass transition) of boron-containing E glass [3]: log . . ( .) h = -+ -698 8788 4 2011 T .The calculation with this equation is in good agreement with the published data from experimental measurements of the viscosity of E-glass at high temperatures (Fig. 1). Due to the presence of calcium and boron oxides in E-glass, the melt viscosity becomes lower than the melt viscosity of sheet glass beginning with the temperature of 1200°C and higher. Nevertheless, accelerants and clarifiers are used to accelerate founding of E-glasses.