Thermal Endurance Tests for Glassware

JSGT_1936_V20_T511_T516

Thermal endurance tests of glassware are all similar, inasmuch as they test the strength of the glass at some position in the piece where the maximum stress occurs under the test conditions. Shock tests are usually employed because of their rapidity and easy execution. There is no essential difference between a temperature “shock” and a straight-line temperature gradient applied across the glass wall of the article. The latter test is of greater accuracy in performance and requires a smaller number of pieces. A simple test for thermal endurance of hollow-ware is described, in which errors of testing are reduced to a minimum. It is recommended that comparison of results should always be in terms of the “average breaking temperature,” which is the temperature difference required to break 50% of the pieces tested. In the type of test described, the breakage increases approximately by 4% for each 1° rise in the temperature difference causing breakage.

J. B. Murgatroyd