Managing Thermal and Physical Stress in the Laboratory

We see very thick glass used for kitchenware such as measuring cups and bakeware. Kitchenware receives minimal heat stress (baking is a slow heating process and therefore is not a thermally stressing activity) and is more likely to receive 

We also see thick and thin glass in the laboratory. Because their concave bottoms could not otherwise withstand the force of a vacuum, filter flasks are made of thick glass. However, do not place a filter flask on a heating plate—it cannot tolerate the (heat) stress. The standard Erlenmeyer, by comparison, is thin-walled, designed to withstand thermal stress. However, a standard Erlenmeyer flask cannot tolerate the physical stresses of a vacuum The flask s concave bottom will flex (stress) and is likely to implode in regions of flaws. 

The shape of glassware can be a clue as to how and/or where it can be used. The more rounded its comers, the better it can diffuse thermal stress. This idea is similar in concept to the sharpness of flaws and can be compared to Eq. (1.1), the stress concentration factor. Although that equation is intended to be used for surface flaws on glass, the principle is the same. 

Examine the surface of the glassware for obvious flaws that may cause 

Heat only borosilicate or fused silicate ware. Never heat a soft glass con- 

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