Glass Annealing

JSGT 1927 V11 T010-T023

If a block of glass, say a cube, is allowed to cool from the hot condition, the outer surface very quickly attains the rigid condition, owing to the rapidity with which hot glass loses its heat to the surrounding air. This question of the rate of loss of heat to the air is one regarding which we have practically no trustworthy data. Anyone who has experienced the difficulties incurred in the measurement of heat dissipation from bodies at a high temperature will understand the reason for the lack of information. There are so many practical difficulties involved in a research of this kind.

James Weir French