A Method for the Measurement of Thermal Diffusivity of Molten Glass

Thermal diffusivity data have been obtained on two typical soda‐lime‐silica glasses in the temperature range from 700° to 1400°C. The thermal diffusivity of a typical glass increases exponentially from 0.016 at 700° to 0.21 cm. 2 per second at 1400°C. The measurement gives the total heat transferred by both conduction and radiation. The glass sample is held in a long crucible having cylindrical symmetry. A small sinusoidal temperature variation is superimposed on the mean temperature of the sample, and the time lag for the sinusoidal heat wave to travel radially from a point on the circumference of the sample to the center is measured. Furnace construction, method of controlling sinusoidal heat input, and methods of measurement are described.