What is Thermal Stress Breakage.
Thermal glass breakage occurs in many circumstances due to its environmental conditions. It is a result of a difference in temperature in two areas in one pane. One part of the glass will expand in the heat, while the other resists the expansion because it is cooler. This causes stress in the glass and when the stress is greater than the edge strength, a thermal breakage will occur.
Thermal stress fractures always start from some tiny imperfection in the glass edge because this acts to concentrate the induced stress. Such imperfections are usually caused by poorly cut glass, glass damaged during handling or improperly glazed. If this is the case, thermal stress will occur at a lower temperature difference.
You can always tell when a breakage occurs due to thermal stress as the crack will always result in a crack of 90° perpendicular to the edge and the face of the glass (as shown above) and will make a curving pattern.
Thermal breakage occurs in annealed glass (has NOT been heat treated) which absorbs heat. Especially in the Autumn, Winter and Spring thermal stress will occur more often due to the drop in overnight temperature. The sun will then rise in the morning and will warm up the centre of the glass more rapidly than the edges. The edges are often protected by frames and awnings so will not heat so quickly.
With glass scratch removal and restoration - due to our 3 step grinding process - thermal heat stress can occur. Our technicians always have surface thermometers on hand to monitor glass temperatures but on very rare occasions thermal stress fractures can occur at much lower temperatures if your windows or doors have been treated as outlined above (poorly cut, damaged during transport etc).
If you have any questions about your glass and thermal stress fractures, please get in touch and we would be happy to answer any concerns or queries that you might have!