Posted By WTaylor Hello all, We've had an incident where the toughened glass door of a tractor has smashed. All witness statements confirm that the glass broke 5 or 6 seconds after the door was closed. Having observed the scene and taken numerous photographs, there doesn't seem to be anything in the cab which could have caused this, and it's highly unlikely anything could have impacted it from the outside. The weather was calm. The door wasn't slammed with any unusual strength. The main theory is that a pebble might have got stuck in the tread of the door and cracked the glass when the door was closed. I thought toughened glass shattered INSTANTLY the moment the surface tension was broken. Is it really possible to have a delay? Thank you, Will

Posted By Jane Blunt The mechanism of failure of toughened glass is that a crack can grow un-noticed, and one day it fails catastrophically. If that has happened here, then closing the door was entirely irrelevant - the glass was about to 'go' anyway! Other causes of failure are damage to the edges and impacts. There is an article here: http://www.glassonweb.com/articles/article/330/ Jane