Sometimes, the "crack" started long before you noticed it. During the glass-cutting process, tiny, microscopic nicks known as "incipient vents" can occur along the edges of the glass. While invisible at first, these small imperfections act as weak points. Over time, the natural expansion and contraction of the house or the window frame can put pressure on these nicks, eventually causing them to spiderweb into a full-blown crack.
You can often distinguish a thermal crack from an impact crack by its appearance. Impact cracks usually have a clear "starburst" point where the object hit the glass. In contrast, a thermal crack typically: double glazing cracked on inside
Double glazing is designed to be tough, but finding a crack on the inner pane of your window can be a confusing and frustrating discovery. Unlike a stray baseball hitting the outside of your house, an interior crack often happens without any obvious physical impact. If you have noticed a fracture on the inside of your double-glazed unit, it is likely the result of internal pressures, temperature shifts, or installation errors. Sometimes, the "crack" started long before you noticed it
Understanding why this happens is the first step toward fixing the issue and preventing it from happening to your other windows. Thermal Stress: The Most Common Culprit Over time, the natural expansion and contraction of