Mysterious exploding toughened glass pane... WTF???!!!

[Lobster]

I ordered a pane of toughened glass about 1.5m tall by 0.5m wide, which I collected today intending to fit it - it's for a fixed light adjacent to a front door.

Anyway, I got the old glass out this evening, cleaned everything up, applied putty to the rebate and picked up the new pane... I was holding it vertically between fingers and thumbs, just lining it up with the frame when suddenly - KAPOW!! without any warning or provocation the whole pane exploded instantaneously in mid air, and landed in a heap of tiny pieces all over my feet. It must have looked like a Tom and Jerry cartoon; I was left there holding out my empty hands with a stunned look on my face.

Clearly I need to have a discussion with the glass supplier tomorrow morning. It seems to me that the pane was flawed in some way - was the toughening process done wrong in some way - plausible? Is this sort of thing common? I'm just envisaging the reaction of the supplier tomorrow

- if he refuses to play ball and tells me I bashed it or dropped it I would like some knowledge at my fingertips!

I'm also concerned at another level - had this spontaneous breakage occurred an hour later the pane would have been in situ and the property empty for the night, and therefore totally open to burglary. And if the glass is so fragile, WTF is the point of paying for it to be toughened?

Would appreciate any comments (before tomorrow!). David

[Owain]

It's not unknown with toughened glass, which stresses as it cools.

The point of paying for it to be toughened is so that it breaks into a heap of tiny and comparatively safe pieces instead of big jagged edges. Toughening is for safety when the glass breaks, not to stop the glass breaking.

If you want to stop the glass breaking (or retain the broken pieces in situ) then you have 4 choices:

1. Laminated glass
2. Wired glass
3. Polycarbonate
4. Translucent fibreglass with embedded expanded metal lath.

Owain

[Andrew Gabriel]

You only have to brush a corner of it against any brickwork or concrete for that to happen, and you'd probably never realise you did that. Double glazing installers do this occasionally, apparently always with the largest and most expensive and most important window unit in the installation. I suppose it might have been left with some strange stresses in it as a result of toughening.

If it wasn't toughened and it broke, you might now be in hospital having got a large glass dagger stuck in you. That happened to a friend of mine in the US -- fell through patio window, and ended up with a long glass dagger stuck in his arm. Besides the fact he nearly bled to death because someone at the scene thought it was a smart idea to remove it, it was 9 months before he started regaining feeling in his forearm and hand, with no assuurance that would ever happen at all.

Laminated glass would be better from a burglary point of view, but unless all your ground floor glass is laminated, there's no point.

[Derek Geldard]

That's the way they go !

My wife had the exactly the same experience with a glass shelf out of a 4 years old kitchen cabinet.

It will have had a flaw in it, whether you notched it in transport or handling or they did will be a moot point.

Small to medium size panes of glass are not very secure. AIUI burglars tend not break in via big panes of glass, too much noise.

It doesn't break into sharp dangerous shards.

As a result of the toughening process the surfaces of the glass are held in tension, if a break occurs in the surface that tension rips it apart as soon as the break in the surface reaches a critical size (when the crack gains more energy from the surface tension by growing than it takes to open the crack it will propagate out of control).

In a shop unit I rent the insurance company insisted I have just such a glass panel protected with a metal grille.

Not much help I fear. :-(

DG

[Richard]

I assume that the glass shelves in my fridge are toughened? Salesman demonstrated their toughness by takeing one out of the shop floor model and chucking it on the floor - it bounced in a most rewarding manner!

Fridge is now seven years old. Perhaps I had better stand by for spontaneously fragmenting shelves, especially as many of them are scratched.

Richard

[Lobster]

Thanks for the replies. Well I suppose since I drove it the short distance from the supplier to the property, I couldn't stand up in a court of law and swear that there's no possibility that the pane could have got notched in transit :-(. Though frankly I really can't see how it could have. I can certainly say hand on heart that I didn't knock it any way at the time it fractured though - I was in the middle of a room and had just picked it up.

Will have to see what the bloke says, I suppose.

David

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Lobster saying something like:

Meanwhile, a boy with an airgun was quietly knotting himself laughing in the bushes.

[Andrew Gabriel]

Wired glass doesn't help prevent glass breaking and does little to hold it together if it does break with any force -- the wires just snap along with the glass. It's mainly to help the glass stay in place for long enough when it softens in a fire that a fire door's 30 minute rating can be met.

[Mike Barnes]

Thus endangering the burglar. We wouldn't want that now, would we?

[Dave Plowman (News)]

It's strange stuff, toughened glass. One staff canteen I used to frequent supplied toughened glass water tumblers and it was quite common for one to explode. But as windows if it survives installation it generally lasts well. After all car side and rear windows are still mainly toughened.

[Dave Liquorice]

Until some scrote comes along with a bit of sharp ceramic or automatic center punch...

'tis funny stuff though. Remeber them trying to craze a car window for a stunt once. Cold chisel held against the glass in a corner, gentle tap with lump hammer, no effect; bigger thump, chisel bounced and was dropped; took some serious welly to finally make it break.

[Dave Plowman (News)]

Yup - same here. Script called for the driver's window to be smashed in with a baseball bat. After take 5 and the stunt guys getting nowhere with it, props fitted a masonry nail to the bat. Worked.

[nightjar]

I recall a woman locked out of her car with the keys visible in the ignition, c 1975, asking a Policeman to break the door window. I had been going to offer to open the door without damage, but thought it better not to demonstrate proficiency with a piece of plastic strapping on a door release knob once she called him over. It took him lots of attempts with his truncheon before the window finally gave way.

Colin Bignell

[Peter Ashby]

;-) reminds of the recent demonstration that it is practically impossible to light a puddle/stream of petrol with a lit ciggy. The alternatives wouldn't look so cool though, would they?

Peter

[Huge]

Whilst I take your point, my Mother fell against our French windows, which we thought were toughened, and weren't. The glass broke into long shards which, had she fallen wrongly, could easily have killed her. Fortunately she didn't and got away with a few stitches.

[Huge]

Nickel suphide inclusions.

toughened glass shatter spontaneously.

[Owain]

We wouldn't, because (a) we might get sued, (b) why add to the distress of being burgled by blood on the carpet.

Owain

[Dave Plowman (News)]

An asp works rather better. ;-)

[Mike Barnes]

That's true, but try telling smokers that they can smoke but they can't light up.

[Mike Barnes]

When it happened to us the blood on the glass was DNA tested and led to the apprehension of the perp. We didn't get sued, but we did get compensated.