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What Made My Window Shatter?

tkingdoll

Penultimate Amazing
T
Joined
Jul 1, 2005
Messages
12,382
Hi all,

Tonight we were sitting down to dinner when suddenly we heard a bang like a muffled gunshot. We looked behind us and the large outer pane of glass of our double-glazed window had shattered.

The window is about 1.6metre x 1metre and both panes are toughened glass.

There was clearly a centre point for the break, towards the right hand side, but oddly there was no hole, no glass missing at all, and no marks to suggest something had hit it.

Added to this, we live on the top floor of a 3-floor block, so the window is probably about 10 metres from the ground, and there is not enough distance from our window to throw a ball or other missile with enough force to break toughened glass, especially without being seen. You'd have to stand in the car park which is overlooked by our block and another block.

The glass cracked into a zillion pieces, all over, but stayed in place. It carried on cracking for about 30 minutes until the glazier arrived, by the time he got there it was about three times as cracked as when it first went, with each piece being between 1 and 10 millimetres wide.

Photos:

http://img237.imageshack.us/img237/5357/9170ja.jpg

That one shows a reflection of my sister, not a ghost. And a closeup of where the crack centre seems to be:

http://img440.imageshack.us/img440/9117/20or.jpg

Today was a particularly hot day for the UK, about 27 celcius (according to our car temp display anyway). We don't have blinds or curtains on the window, which faces NW ish. We get a few hours of sun on that window in the early evening.

No-one saw any kids or anyone running away from the scene, but we cannot rule out an airgun or catapult, but I would have expected that to leave a hole in the glass and a missile on the ground, of which there were neither.

There was no dead bird or feathers either, and, as I said, no marks on the glass where something might have hit it.

A few months ago there was some scaffolding erected for external cosmetic refurbishment to the exterior of the building, it's possible I suppose that a spot of damage was done by the scaffolders, but I have cleaned the interior window since then and didn't notice anything on the outer pane.

We have also had a window cleaner recently for the first time since we've lived here (about a year), so it's possible damage could have occured then too, but unlikely.

The windows are about 10 years old, double-glazed with UPVC frames, but the building is about 40 years old.

So, what caused my window to spontaneously a splode?
 
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I slipped and fell off the ladder.

What? You invited us to "see your dinners" ...

... and the way you eat broccoli is HOT.
 
My guess is that it was the sound. Perhaps aided by some earlier stress from cleaning, or the other things you mentioned (someone bumped the glass and weakened it perhaps).

Do you know if any other windows in the area were damaged? That would tend to confirm the sound theory. If not, I'd lean more toward some type of projectile that happened to cause the break while leaving little direct evidence.

I once broke a storm door window by setting off a "Cherry Bomb" in the ditch in front of the house. Mom was not amused.

Cherry Bombs are those round red fire cracker thingies. Quite a bit more powerful than a normal fire cracker though.
 
This Guy said:
My guess is that it was the sound. Perhaps aided by some earlier stress from cleaning, or the other things you mentioned (someone bumped the glass and weakened it perhaps).

Do you know if any other windows in the area were damaged? That would tend to confirm the sound theory. If not, I'd lean more toward some type of projectile that happened to cause the break while leaving little direct evidence.

I once broke a storm door window by setting off a "Cherry Bomb" in the ditch in front of the house. Mom was not amused.

Cherry Bombs are those round red fire cracker thingies. Quite a bit more powerful than a normal fire cracker though.
Click to expand...

Sorry, I should have made it clearer. The sound was the glass breaking. There was no other noise, not even of people running away.

The smaller window next to it was wide open and we live on very private enclosed grounds, so we would have heard if anyone was around.

No other windows were damaged, there are 24 windows plus glass doors on the front of my building and the same on the building opposite (which you can see reflected in the glass).
 
A couple of quotes from this site;

Soda-lime glass is normally used for windows. Annealed float glass is the most widely used and least expensive. Heat-strengthened glass can have twice the strength of annealed glass. Tempered glass, which can have twice the strength of heat-strengthened glass, is often used where safety glass is required. While most glass breaks into large pieces, fully tempered glass produces small cubic pieces when it shatters.21 On rare occasions tempered glass suffers spontaneous breakage, apparently because of microscopic inclusions in the glass.
Click to expand...
Tall buildings, particularly those with irregular shapes, are subjected to complex wind pressures at building corners and along the faces.
Click to expand...
So it could just have been a microscopic flaw in the glass which deteriorated with time, until something like a sudden change in wind direction altered the pressure on the glass, and the flaw gave up the ghost.
 
wollery said:
A couple of quotes from this site;


So it could just have been a microscopic flaw in the glass which deteriorated with time, until something like a sudden change in wind direction altered the pressure on the glass, and the flaw gave up the ghost.
Click to expand...

Cor, it says "rare". That's exciting!

My rare (and therefore special) spontaneously asploding window could be worth millions!
 
I'm with wollery. And that shatter pattern looks very familiar.

I used to work as an amusement technician -- I drove around the state repairing coin-operated machines, video games and pool tables and jukeboxes and pinball tables. That heavy sheet of glass that covers a pinball table's playfield is tempered, as your window appears to have been tempered.

Not once but twice, once in the shop (bad enough) and once eighty miles away (eeep! =>_<=) I was sliding a playfield glass into or out of a table when, without warning, it shattered in my paws. In a fraction of a second I went from a confident, competent tech to a "Duhhh!" poster child holding two half-cookies of glass and looking down at a really unpleasant cleaning and repair job. I was told by the old-timers that this kind of thing just happened, sometimes even with nobody nearby, sometimes when coffee was spilt on it, etc. They all agreed that any scratch might develop into a flaw that would some day go SPANG! and give a surprise to some unsuspecting repair-critter.

The pattern of shattering was very much like that in your picture. Except most of the glass crumbled into chunks on the playfield.
 
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Sounds like Wollery and Meffy have the answer.

I wouldn't rule out some assistance from a bird, that banged into it, perhaps got knocked out, and then recovered, cussed a bit, and flew off ;-)

Might watch the neighborhood for a bird that appears to have a hangover! ;)

Being 3 floors up, any feathers that became dislodged could easily have blown a good distance away (with the aid of a slight breeze even).

But perhaps I've seen too many of those window cleaner commercials, where the birds keep banging into the windows ;)
 
You mentioned the heat, so I'll offer one other option. I've had glass "asplode" due to one side heating up really fast compared to the other side and the difference in expansion rates of various parts resulting in a split. It would still radiate like that because the split would still happen at one specific point, though there would probably be a distinct line through it, and from there I dunno, it became fragile enough that cracks started forming? Had the air conditioning on full blast that day, as I would have?

It's a possibility to consider anyway...
 
Dark Jaguar said:
You mentioned the heat, so I'll offer one other option. I've had glass "asplode" due to one side heating up really fast compared to the other side and the difference in expansion rates of various parts resulting in a split. It would still radiate like that because the split would still happen at one specific point, though there would probably be a distinct line through it, and from there I dunno, it became fragile enough that cracks started forming? Had the air conditioning on full blast that day, as I would have?

It's a possibility to consider anyway...
Click to expand...

Yeah, I mentioned the heat in case anyone knew if that could be a factor.

The internal temperature wasn't much different though, most UK homes don't have air conditioning. It doesn't get hot enough for long enough :(
 
tkingdoll said:
Yeah, I mentioned the heat in case anyone knew if that could be a factor.

The internal temperature wasn't much different though, most UK homes don't have air conditioning. It doesn't get hot enough for long enough :(
Click to expand...
You also mentiond that the window next to the one that shattered was open, so there likely would be very little heat differential between the inside and the outside.
 
Do windows in the UK normally have safety glass? Never seen that here, except in vestibule door glass and auto glass, of course.

Anyway, I think probably a large bird, they can take quite a hit and still fly off, just look at this video. That seagull flew off shortly after!
 
Hmm, the other option is if it was that hot then it expanded to the point where it pressed too hard against it's own frame and shattered from that pressure. I'm leaning more towards the technician's opinions of course, but I like throwing options out there.
 
Could well be a combination of factors too. Shame there wasn't a high-speed camera aimed the right way at that time. Oh, lost opportunities!
 
It really sounds as if it were tempered glass.

http://en.wikipedia.org/wiki/Prince_Rupert's_Drops
 
[CT]
The window did not shatter, it was a controlled demolition perpetuated by a diabolical worldwide conspiracy the likes of which have never been seen before.

Is Larry Silverstein involved w/ your building in any way?
[/CT]
 
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