Re‐Evaluation of Glass Viscosities at Annealing and Strain Points

Abstract

A review is presented of the early work which led to the present definitions of the annealing and strain points. New tests on the same primary standards, with modem apparatus and corrections applied for expansion, indicate that the definitions should be modified. A recommendation is put forth regarding such redefinitions, by which the viscosities at the annealing and strain points would be 10 13.00 and 10 14.60 poises, respectively, during cooling at 4°C. per minute.