| From: Alex Brislan | 7/07/99
17:49:02 |
| Subject: Spontaneous breaking glass | post id:
22289 |
| Last week Karl was answering a
listener's question on a car window glass that spontaneously broke
(outwards I think). Karl described tempered glass as having a layer of plastic sandwiched between it, but my building design lecturer said this is 'laminated glass'. Tempered glass, I'm told, is cut to size first (unlike regular float glass), then heated, then cooled rapidly. The outside cools first and shrinks, applying a compressive stress to the inside. Then the inside cools, shrinking away from, and applying tensile stress to, the outside. This permanent stress is what makes the glass break into small pieces, and why it's used for cars. A small defect in the listener's window glass may have worsened over time, until as little as a puff of wind may have released the imposed stresses, resulting in the spontaneous breakage. | |
| From: Michael Gunter | 7/07/99
23:36:02 |
| Subject: re: Spontaneous breaking glass | post id:
22338 |
| When I was a kid, mum had some
"Crystolac" brand tumblers, French I think. They were very durable and
bounced when you dropped them. One day she dropped a teaspoon into one and the whole tumbler exploded into small pieces of glass all over the kitchen benches and floor. Luckily nobody was hit in the eye by flying glass. They say hell is where the French are engineers, the British cooks, and Germans are the police force. | |