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Q & A: suddenly shattered glass

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Most recent answer: 04/08/2016
Q:
Can you explain this?Hello,We had a phenomenon happen recently(Tuesday the March 15th) about 8:30 PM that is inexplicable to us, but there must be some explanation. My wife & I were in separate rooms when we both heard an extremely loud noise from the living room! The noise sounded like a large glass that just hit a hard tile floor, but loudness was magnified.As it turned out we came into the living room to find a glass platter that we had sitting on the coffee table for about a year just shattered. �It broke completely by itself as there was no one in the room. Do you know how this may have shattered/blew apart all by itself?We used the platter to put 3 little oil lamps on.Inside our house the next morning at 6 AM we heard thunder outside so thought it might have had something to do with the barometric pressure.Very low barometric pressure & the type of glass it was made up combined just right to explode it like that? The temperature was a constant 68 degrees as it was for the months that was on the table.If you have any idea about this, we would appreciate it.Thank you,David H*I took some photos of the shattered platter. �will send them if you wish.
- Dave (age 60)
MN
A:

This reminds me of a personal story. The rear window of my parents' Volvo spontaneously shattered when the car, only about 20 years old, was sitting in the garage. My dad, who was around 90 at the time just shrugged and said "Well, what can you expect when something is so far out of thermal equilibrium?"

Glass, particularly certain types of tempered glass, has some strong internal strains because parts of it cool and become rigid before other parts, so that the shape doesn't adjust properly as the last parts cool down and shrink. In other words, parts of the glass are compressed more than they would be in equilibrium and other parts are stretched more. Small defects and uneven thermal strains (those little oil lamps?) can sometimes trigger a little crack to start to tear, allowing the shape to change releasing that strain. Typically, for tempered glass that leaves lots of smallish pieces, not just a few big cracks, because there's strain throughout the glass. I guess something like that happened with your platter.

Mike W.


(published on 04/08/2016)

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