Thermal shock

Glassware in coffee brewing equipment is exposed to thermal shock when hot water, or coffee is poured into glass beakers, carafes, or other recipients. In order to solve the problem with glass cracking, manufacturers use borosilicate glass, which is resistant to thermal shocks.

Thermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts. This differential expansion can be understood in terms of stress or of strain, equivalently. At some point, this stress can exceed the strength of the material, causing a crack to form. If nothing stops this crack from propagating through the material, it will cause the object’s structure to fail.

For cold brew coffee preparation there is no need to use borosilicate glass, since the thermal shock is minimal, even with refrigerated steeping.

A good example for thermal shock is the French press. When hot water is poured into the glass beaker, the sudden change of temperature might cause the glass to crack.