Can somebody explain why this happened

Gday Kim
If it happened in Scrubby Town I wouldnt be blameing the weather.....It would be a cultural problem??
Maybe a small unseen crack already just waiting for a change in weather to bare its ugly head???


Cheers

about 18 years ago it was cold and drizzling rain and I pulled up at the shop to return a video and had left the car running with the back window demister/heater on and while I was in the shop heard what sounded like a bomb going off. Ran outside and the back windscreen had bleep tered. Two toddlers in their car seats scared but OK. This was in my mitsubishi magna. Never did that again.

Kim,

When I was coming back from the EO Gathering I watched a rock comeup and mack the windscreen just at the bottom but didn't break and I thought at the time how lucky it was. Three weeks later same thing a frosty morning with demister on and a small cracked started and I knew it was right where that rock hit. ye the time I got to work (3Km) the crack had travelled full width of the windscreen. lucky it is below the wiper line so I will not hurry to replace it.

I recall dr Karl on JJJ explaining funny things about glass one day. From memory, the question was why do some glasses drop on the floor and not break, yet some break in your hands while washing up. It basically comes down to the straw that breaks the camels back. glass will eventually bleep ter just due to the atoms in the atmostphere crashing into it constantly, but it will take a hell of a long time. Every knock does some damage to the structure of the glass, a big impact may not break the glass, but will weaken it, and later it may be broken by a smaller impact.

In this case it may be as others have said, caused by a previous impact (not nesesserily in the same plase as the crack), or the windscreen may have been under some tension due to the way it was fited or chasis/body flex; the change in temperature may have been the straw that broke the camels back.

Cheers Andrew