OH content dependence of viscosity of vitreous silica

Viscosity of various types of vitreous silica was measured by a cantilever-beam-bending method having been used in industry. The viscosity measured by this method agreed with the value measured by a standard beam-bending method for the same sample, and temperature dependence of viscosity are consistent with those reported in literature using various measurement methods. OH content dependence of the viscosity at 1200 °C was measured. There are two groups of vitreous silica, each of which can be represented the viscosity by a decreasing function of OH content; one group is fused quartz (FQ) produced by melting natural quartz powder, and another group is synthetic fused silica (SFS) produced by flame hydrolysis of SiCl4. The viscosity of FQ is higher than that of SFS at the same OH content.