Viscosity of potassium boro-silicate system in glassy and liquid states

A new method, round-ended tube penetration/rotation method, was developed for the continuous measurement of the viscosity from the glassy to liquid state. The reliability of the new method was tested by the measurements covering the glassy to liquid states of boron trioxide up to 1250 K and compared with previous studies. The agreement with the previous data was within errors of ±20% in glassy state and of ±10% in liquid state measurement. The viscosities of potassium meta- and di-silicates containing boron trioxide up to 50 mol%, and pseudo-binary system of potassium tetra-silicate and potassium tetra-borate were measured. The relationship between viscosity and composition is similar to that of the sodium boro-silicate system. The potassium boro-silicate system has a greater tendency to crystallization than that of the sodium boro-silicate system. Consequently, the comparison of the viscosity between both systems could only be done over a liquid temperature range.