Further Studies on Methods for Determining the Thermal Endurance of Glass

JSGT 1937 V21 T463-T475

Tests have been carried out to determine the difference in the thermal endurance values obtained when test pieces of glass rod are heated, under conditions otherwise similar in a furnace in the horizontal and vertical positions respectively. The average thermal shock values for fifty specimens, obtained for glasses of low thermal endurance, were, for the two furnace positions, within 2°, but for “Pyrex” rods there was a difference of 15°, the tests in the vertical furnace giving the higher values. The thermal shock values decreased with increasing diameter of rod, the relationship appearing to be hyperbolic and tending to a finite positive value as the diameter increased. The results of previous workers were shown to fit similar curves. A suggested “standard procedure” for thermal endurance tests is given.

R. J. Waller