A Lucky Escape

Glad my favourite knitter is ok :slight_smile:

Unrelated but similarly unexpected - about ten years ago we had a Smeg oven - still under guarantee - put it on self clean and not once but twice, the glass door exploded all over the kitchen. It was very lucky that none of the kids were around at the time. Never buying another Smeg!

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Horrors, that is terrifying.

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Jane, I have glass shelves and windows that are at least 60 years old. They don’t die of old age. Some externally applied force/energy causes them to crack or shatter IMO. 樂

I have a Smeg, range, but it is not a pyrolising one.
The oven takes a long time to come to temperature, so I use the old one that came with the house, that does pyrolise, but have not had any bad experience, so far.
Likewise, I am glad no one was hurt.
Jim is trying to get all the glass from the barn floor, which I can imagine will be difficult. He does not want punctured tyres on the ride on mower.
I am knitting a dress for a three-six month old baby girl due on the 20th September, it has a square yoke with lots of bobbles and the dress part is knitted in the round.
I got the pattern for Knitting for Olive, lovely stuff from Denmark.

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Well, I can only imagine it has been the extreme change of temperature, but the bathroom is on the north wall of the house and the other one exploded in the barn just under a day later.

This article may be useful??

I’m now seriously think of putting some sort of plastic film on the inside of my shower screen so that if mine shatters I won’t be covered in glass.

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When we thought about this, these panels are fifteen years old.
The first panel shattered whilst attached to the frame around the bath and the second one had been taken into our barn and exploded about eighteen hours later, in a totally different surrounding and no tension on it at all.
Thank you for posting this though.
It does seem that taking a shower can be one of falling glass particles instead of water!

This could open up an interesting discussion on “synchronicity” versus “coincidence”. Did the second panel succumb to terminal “grief”? :thinking::upside_down_face:

I am not sure if it was just physically or emotionally shattered Peter.

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A typically Williamsonian reply, Jane: measured, considered, empathic, timely, succinct and nicely personalised to gratify and stimulate at the same time!

A template and example to us all. Thank you. :hugs:

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Perhaps, but trying to prove it after fifteen years and it is all in pieces might prove a step too far.

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I wasn’t meaning in order to pursue them - I find glass fascinating and there’s presumably some physical explanation, I’d love to understand it.

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? Chauve-souris :bat::bat: Ultrasound ?

My 1.8m x 70cms x 9mm thick screen exploded in millions of bits, one of which drew blood from one of the guys fitting it. Like Jane’s it went off with quite a bang. Jose staggered out, bleeding [not alot] but very shocked, as were his two amigos standing amongs a huge pile of fragments.

The cause was disappointing in that the guy nipping up the pinch screw at the screen end of the rail coming off the wall should have known that you mustn’t nip up metal fixings directly onto glass. He should have added padding of some sort. There was probably a rubber fitting in the bag of bits

The pressure came right in the very top corner, about 10mm from side and top but the entire screen blew apart in a millisec.

Jane’s screen must have been accumulating some stress in the glass. This would explain why the remenant fragmented.

Or did the screen have a metal channel running over one edge of the glass? Top or side. If secured by metal fixings, these might have expanded a wee bit - v hot weather? This would cause the screen to fragment if they bore on glass.

These screens are designed to fragment like the old ‘saftey glass’ windscreens. Millions of bits but not of the slicing kind.

I actually watched the stone thrown up by the car in front head for the windscreen of my van. When it hit - it was about the size of a broad bean, the whole screen - some 2m x 55cms - shivered into millions of crazy bits but stayed put. As I was doing 65 on the M23, this was tricky but better than being on a country lane.

I had to punch a hole in this mess to see but got onto the hard shoulder safely. The annoying thing about this was the car that threw the stone at me was not supposed to be there. He, plus his 2 pax, was supposed to be sitting in my van. He decided to take his car, instead.

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Glass is interesting in that it is not a solid but actually a supercooled liquid, it is very weak under tension (because the bonding between its constituent atoms is not that strong, technically still being fluid) but pretty strong under compression.

This means that any crack tends to propagate fairly quickly - stress is concentrated at the top of the crack which literally pulls the material apart. It is also pretty brittle so it is easy to get a crack going and sheet glass will shatter fairly easily into large pieces with sharp edges.

The descriptions of glass “exploding” sound like toughened class though.

Toughened glass is made by cooling the surface of a piece of glass rapidly - before the core has chance to solidify - the result is that the more slowly cooling core wants to contract as it cools but has to pull on the surface to do so; this puts the surface under considerable compression (and the core under tension).

As I said glass under compressive forces is very strong which results in the robustness of toughened glass products. It also means that if you do get a crack to propagate into the core the tension within gets released explosively - the glass typically breaks up into the telltale small hexagonal pieces.

So toughened glass is mandated anywhere people or objects could hit the glass - not only is it stronger and less likely to shatter but does so “safely” without lots of sharp edges.

The strength sometimes leads people to do rather stupid things such as throwing themselves against windows to show how strong they are with eventually fatal results.

The most extreme example are Prince Rupert’s drops - made by dropping molten gobs of glass into water resulting in tear shaped pieces with long tails. The bulbous end can be hit with a hammer without breaking but snap the tail and the whole thing “disappears” as the internal stresses shatter it into dust sized fragments.

As you say interesting stuff

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Well then, here’s a story about glass behaving exactly the opposite of all these exploding panels.

I was staying with friends in London. Their house is at the end of a cul-de-sac. People frequently drive in by mistake and have to turn round under the windows where I sleep. Their headlights do a Fandango round the ceiling.

On this occasion, about 1a.m., the car came down, turned round but did not drive off. It stayed put, 20m from the end, lights on, in neutral, with the engine screaming at full revs.

After 5 mins of this clearly something was wrong. I went to check. The driver was slumped over the wheel, out. Gone. I banged on the side window. I banged on the windscreen. Nothing. This brother was away, nah.

The car was screaming its head off. His foot was hard down. I was impressed how it didn’t blow up. It smelled dangerously hot.

Heads started appearing and I asked one to call Plod. A few mins later a patrol car arrived. I explained the situation. Our constable drew his truncheon and banged smartly on the window, then windscreen. Nuttin’ goin’ to disturb me sleep, nah.

Somehow, the driver had activated the locks. The officer decided he’d better break in. The Met’s finest truncheon was deployed with maximum force to the r.o.s window. Nada! Resisted all that our man could throw at it! Repeated stern banging got nowhere.

I mentioned that my host was in the tree business and in a jiffy I could provide a piece of heavy metal.

I reappeared with a pick axe. The constable, taking no chances that his window smashing technique was deficient, stepped back two paces, wound himself up and launched a massive swing at the window behind the driver’s head.

Smash! Glass everywhere! Engine still screaming. No reaction from the driver.! Was the man dead?!

Policeman killed the ignition, the screaming stopped. Maybe it was the sudden quiet that woke the man from his coma.

I put the pickaxe away and went back to bed.

Fantastic as it was, my friends, whose bedroom directly overlooked the scene, had heard nothing!

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Excellent if you look at them through a polarised lens - I made some in physics years ago, great fun. I love glass. Lightning glass is cool as well.

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