At Read Consulting borosilicate glass expert has extensive experience performing borosilicate glass failure analysis. In addition, studies have been performed on glass composition and thermal shock testing. This includes testing first articles of various parts from overseas suppliers. Items tested include oven doors, glass oven ware and various glass carafes. Borosilicate glass has a lower coefficient of thermal expansion, and this makes it., when fully annealed, more resistant to thermal shock. On the other hand, its impact resistance is identical to soda lime glass. Thin-walled containers, such as coffee press carafes, can be readily damaged by metal spoons. At the damage site the stress is concentrated. This causes normal forces to cause a crack to grow to failure.
In this example, the subject carafe ( 2.5mm thick glass) was damaged on the inside wall at the heel, Subsequent use caused a crack to grow to failure. It appears as if a hard object, such as a metal spoon, caused the damage. Do not stir the contents with a hard object.