Calculation of the viscosity-temperature relation of glasses and measurement of glass and glaze viscosity by the needle penetrometry method

Viscosity of oxide glasses can be related to temperature by using the chemical composition as far as the glass structure maintains well-known cation environments. Some models were presented in the literature for common container and flat glasses. In this study, we present 7 models, which are valid in narrow compositional ranges Of SiO2, Al2O3, Na2O, K2O, CaO, and MgO. An intersection of these domains was found with the glass SiO2 74%, Na2O 15%, CaO 9%, Al2O3 2%. This average glass was used to compare the response of each model against temperature in the whole viscosity-temperature range (3<Log eta(dPas.s)<13; 600-1700degreesC). In general, model variations are similar but moderate discrepancies of viscosity (about +/-1Pas) reduce the significance of model comparison. As the average glass composition minimizes model differences, it was considered that this glass behaviour is valid in the whole range. This average was used to calibrate a simply designed equipment for measuring viscosity in the 900-1200degreesC temperature range by the needle penetrometry method. It was shown that this method is useful for ceramic glaze characterization in a large temperature range.