Under what conditions can glass crack spontaneously?

[Ophiolite]

EDIT ... but they are OK on Chrome

And Firefox.

 

[collinsmark]

none of your videos nor their links are showing ... nothing to watch

I can view them on Microsoft Edge, Chrome and Firefox. It could be that your browser's video codec crashed. You might want to try closing and re-opening your browser. And if that doesn't work, maybe reboot the computer.

 

[davenn]

Tis dark here at the moment ... will post a pic in the new day

OK a couple of images
I have drawn a parallel trace beside the crack. Note the crack is a single crack ... there is no splaying out of cracks as seen in post #24
and also obvious, there is no shattering. I have looked very closely and cannot identify any impact site.

First image is the left hand side of the crack (out towards the centre of the windscreen
where my trace turns black is where it continues into the next pic.

image #2
right side of the crack. it continues right to the rubber window seal. you can see that this section of the crack is just a very smooth
"S" shape

Dave

 

[CWatters]

That's a front screen so most likely it a laminated screen which behaves very differently to toughened glass. Did the crack start at the edge? If so it could be edge damage caused before screen even fitted to the car.

 

[Asymptotic]

I have drawn a parallel trace beside the crack. Note the crack is a single crack ... there is no splaying out of cracks as seen in post #24 ...

Some of these lines may be crinkles in the label, but others look suspiciously line small cracks in the windshield. If they are, did the major crack occur shortly after the inspection sticker was applied? Could the mechanic have been a wee bit ham-handed?

 

[davenn]

Some of these lines may be crinkles in the label, but others look suspiciously line small cracks in the windshield.

Follow the paralleled white line that I drew on the image just below the crack ... that is the ONLY crack in the glass ... a single clean curved crack
That label has been on since the car was manufactured 5-5.5 yrs ago the cracks in it is because of the hot Aussie summers often exceeding 40C

To the left of this nice smooth curved section is the more meandering crack that expands in little bursts every few days or so
that is shown in the first image in my previous postDave

 

[collinsmark]

As @CWatters mentioned, the front windshield is usually made from a different process than other car windows. The front windshield is usually not tempered, and instead made from laminated glass. Laminated glass is made by sandwiching plastic in between two sheets of non-tempered glass.

There's good reason for that. If the front windshield was tempered glass and did shatter, it would heavily obstruct the view in front of the driver. Therefore, laminated glass makes the better choice for this window (or windshield). When it does crack, the cracks are typically isolated, clean cracks rather than the spiderweb pattern of tempered glass. 'Makes it much easier to see through when cracks happen. Additionally, any debris that hits the windshield might only break the outer layer (of the laminated glass) and not puncture through the window and hit the driver who is in control of the vehicle.

 

[davenn]

The front windshield is usually not tempered, and instead made from laminated glass. Laminated glass is made by sandwiching plastic in between two sheets of non-tempered glass.

yup, that appears to be the way these days ... but it wasn't always like that ..

There's good reason for that. If the front windshield was tempered glass and did shatter, it would heavily obstruct the view in front of the driver.

and I have been in that situation a few times in years gone by ... down the road at 100km/h and boom, zero visibility ... not fun!