Determination of the viscosity-temperature curve for glasses on the basis of fixed viscosity points determined by hot stage microscopy

This work establishes a method for obtaining the viscosity-temperature curve for glasses on the basis of the characteristic points obtained by hot stage microscopy and the comparison with the viscosity-temperature curves measured with a high temperature viscometer. Viscosity-temperature curves were determined for three commercial glasses of certified composition and two experimental borosilicate glasses in the interval of 550-1500°C using a high temperature viscometer adjusting the values to Vogel-Fulcher-Tammann curves, VFT. Temperatures corresponding to the characteristic points of first shrinkage, maximum shrinkage, softening, half ball and flow were determined by means of hot stage microscopy together with their corresponding viscosities on the basis of the VFT curves for each glass. With these results the degree of viscosity corresponding to the characteristic points obtained through hot stage microscopy is determined together with the error for each point of viscosity in the interval between logη=10 and 3-4.

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