Foggy windows, or blown glass as the event is sometimes referred to, typically occurs within double glazed panels of glass. The most common cause is window seal failure, which can take place if the frame is exposed to higher than average temperatures on either side of the scale. Although modern seals are made using rubber silicon compositions heat and cold can cause warping, which can weaken the atomic structure.
What does this result in?
Once the seal solidifies again, it can sometimes split, especially if it warps out of shape. Initially this may not be noticeable, but over the course of a few days (or even a couple of weeks), one or both panels within a double glazed window can begin to take on a foggy appearance. In these cases many home owners find themselves asking if glass repair is an option. Unfortunately, the only fix in these cases is to replace the damaged panel.
Why is this?
The foggy appearance is actually the expulsion of part of the atomic structure present within glass. Any good glazier will tell you that glass is made from silica, which is extracted from sand grains. In order to make glass, the silica is mixed with soda ash and other chemicals – and it’s the emission from the ash that can lead to fogging. Unfortunately there isn’t a way to restore the ash, without completely destroying the window.
If a panel has suffered with fogging the only option is glass replacement – which should be performed by a fully licensed glass expert. Once the new panel has been fitted, the seal should be replaced and then pressed into position to ensure that A) the pane is able to function as expected and B) heat and cold are able to be controlled in order to avoid any further warping from taking place.