Clay Bars / Windscreens.

[Poorboy_racer]

Some time ago I put a post up on here saying soon after using a clay bar on my mini windscreen it smashed, I suggested there may be some link. The response was such that I felt silly for putting that post up in the first place. Most of the responses were along the line of…….you idiot, how could a clay bar possibly do anything to your windscreen? As I didn’t get one single response accepting that it was a possibility, I thought ok, maybe it was a coincidence. This weekend was a British Car show (no jokes about piles of rust and broken down cars thanks) I had decided to take the Mini to. As the screen was getting a bit hazy I thought ok I will try the clay bar on it. It bought the screen up a treat, very clear. Set off and as soon as I got on the freeway guess what? No stone hit the screen, nothing, it just shattered!
Exactly like last time. I know people do use clay bars on windscreens and I can’t find any references to them smashing so maybe its unique to classic Minis or something, anyway, Im never using it on glass again. Im convinced that it had to have done something, no idea what or how. Im writing to the manufacturers, there is no warning about not using it on glass, I will post the response (if I get one) here. Fortunately I did have a spare screen that’s now been fitted. Not happy about all the chards of glass in my cars vents and scratches on the bonnet, though.

[GT450]

I have used it on y screen with no problems. Is it possible your shell is distorting and causing the screen to shatter especially as it's not a laminated one . I think you're looking for an answer in the wrong place. My thoughts.
GT450

[lockieoc]

Have to agree with GT450. There is nothing in the spray retailer or the clay that would cause the windscreen to fail like this.

[Pepscobra]

How hard were you pressing when using the clay bar?

Only thing I can think of is that you were pressing way too hard with the bar. You only need to slide it across the surface for it to do its thing.

By the looks of it, that windscreen is much flatter than the modern day windscreens and if you put too much pressure on it, you were probably flexing it and weakening it.

Coincidence? I think not. The clay bay on its own would not have done a thing, but if you were pushing too hard, then thats your answer.

[Poorboy_racer]

No. First time I used it, the windscreen shattered the first time I drove the car and exactly the same thing happened at the weekend. First drive after using it. Can’t be anything else. I know more modern cars use the glass as a structural element and therefore I would imagine they are probably stronger than the screens used on a classic Mini but the screens are laminated it says on the screen PERMA SAFETY GLASS APP’D A.S. R1 Lic.88 T-P so they are to an Australian Standard. I have only used a clay bar on my windscreen twice and both times same result……broken windscreen 1st drive. Coincidence both times I don’t think so. Also these two events happened at least two to three years apart. It’s not like the car twists and gets through loads of windscreens. I have had the car a long time and only ever had two broken screens both immediately after using a clay bar. I reiterate a rock was not thrown up and hit the screen ether time. It just shattered both times with nothing hitting it.

[Poorboy_racer]

Pushing too hard! Your kidding. How many stones bounce off your screen during its life? Dont think thats possible. Anyway I do know how to use a clay bar and no did not press hard with it just a gentle glide like the instructions.

[JADED6]

Odd. So, just to make sure... It had been driven with the new screen on without breakage before you used the clay bar for the second time resulting in the second breakage? (proving body twisting isn't the issue?)

[galaxy xr8]

That's one for Scully and Mulder , weird.

[Poorboy_racer]

Odd. So, just to make sure... It had been driven with the new screen on without breakage before you used the clay bar for the second time resulting in the second breakage? (proving body twisting isn't the issue?)

Correct.

[chamb0]

Originally Posted by Poorboy_racer

Correct.

At freeway speeds as well?

Sounds silly but maybe walk us through every step you took in treating the windscreen, that you would have done both times.

Sounds like one for Dr Karl.

[Poorboy_racer]

Washed the car. Sprayed lubricating fluid on the windscreen. Manipulated the claybar in hands to soften. Glide claybar across screen. I did do it outside on a sunny day but it was in shade and not horribly hot or anything, (same place the photo was taken). Got in the car about an hour later. Drive approx 10ks to the freeway. Got onto the freeway and up to 100kph after less than 15mins BANG! Shattered windscreen. I do accept that a Mini screen is more vertical than most other cars hence the ‘flying brick’ nickname of Minis but the clay bar had to have done something. Incidentally it was the same bar used both times Meguiar’s Quik clay. I will put a post up on the Ausmini web site to see if its happened to any other Minis.

[OzJavelin]

Got any mates with any old parts cars you could try the clay bar on again? Most screens are laminated so might not be the same test but ..
Personally I doubt it's related, but might be worth at least worth testing .. and if in doubt don't do it on your car again

[jpd80]

Originally Posted by Poorboy_racer

Washed the car. Sprayed lubricating fluid on the windscreen. Manipulated the claybar in hands to soften. Glide claybar across screen. I did do it outside on a sunny day but it was in shade and not horribly hot or anything, (same place the photo was taken). Got in the car about an hour later. Drive approx 10ks to the freeway. Got onto the freeway and up to 100kph after less than 15mins BANG! Shattered windscreen. I do accept that a Mini screen is more vertical than most other cars hence the ‘flying brick’ nickname of Minis but the clay bar had to have done something. Incidentally it was the same bar used both times Meguiar’s Quik clay. I will put a post up on the Ausmini web site to see if its happened to any other Minis.

Ohhhhh Deja Vu--wait a minute, that sounds like a older zone toughened conventional screen,
I had a friend go over one in an early Cortina with a buffing wheel and the same thing happened to me.

[Pepscobra]

Originally Posted by Poorboy_racer

Pushing too hard! Your kidding. How many stones bounce off your screen during its life? Dont think thats possible. Anyway I do know how to use a clay bar and no did not press hard with it just a gentle glide like the instructions.

Sorry mate if you think that was an unreasonable suggestion, just trying to help with a logical answer... How do you know you weren't pushing too hard? How hard is too hard? I've never seen you clay before.
When a rock hits the windscreen, it is a very concentrated impact to the glass and unless it's a pretty big rock, it will only make an impact where it hits.
If you were pressing too hard with the clay bar for a sustained period of time you could have been flexing the glass without even realising it.
As I mentioned, that windscreen looks a lot flatter than the modern car convex screens, meaning it would be inherately weaker.
If I'm not mistaken, windscreens are tempered and/or laminated glass right?
Tempered glass can not take much movement before it lets go. I work in construction and have on two occasions seen panels of tempered glass just explode as they were being installed because it was flexed beyond its tolerances.
Have you spoken to the supplier and/or a glass expert?
Here's you solution... don'y clay bar it again.

[Pepscobra]

Originally Posted by jpd80

I had a friend go over one in an early Cortina with a buffing wheel and the same thing happened to me.

That could have been due to an uneven heat build up in the glass from the buffing wheel. Have heard of that happening too to tempered glass.

[superfly]

Sounds weird.

But why would you clay bar a windscreen? Just washing it, cleans it up nicely. And some RainX to remove the rain.

[Poorboy_racer]

Lots of people clay bar windscreens. The car is 40 years old. The windscreens must be quite old (no idea of age) they build up ingrained dirt like your paintwork that you just cant get off. A clay bar will lift it and leave the screen really clear. Sometimes a simple wash which is all I will do from now on, just dosnt cut it.
As for pushing too hard, no offence taken. I to work in the constuction industry to a point. I design buildings and I do understand what you are saying. To be honest I have put a great deal more effort 'elbow grease' into cleaning the windscreen without using a clay bar in the past with no issues.

[mik]

mmm weird, hit any pot holes while on route to your destination?

[Poorboy_racer]

mmm weird, hit any pot holes while on route to your destination?

Probably, and the hydroelastic on my mini could do with a pump up. But not on both occasions. And No problems with the screen I replaced the broken one with. Went on a 300k round trip on Sunday with the new screen in, with 3 people in the car and did hit some potholes hard enough to bottom out the car (not going slowly). I didn’t hit a pot hole when it shattered.

And before someone suggests it NO I didn’t throw the clay bar at the screen.

[Pepscobra]

Hang on a sec... Is your name Mark?
If it is, I think we may know each other...

[ozpacman]

Originally Posted by Pepscobra

How hard were you pressing when using the clay bar?

Only thing I can think of is that you were pressing way too hard with the bar. You only need to slide it across the surface for it to do its thing.

By the looks of it, that windscreen is much flatter than the modern day windscreens and if you put too much pressure on it, you were probably flexing it and weakening it.

Coincidence? I think not. The clay bay on its own would not have done a thing, but if you were pushing too hard, then thats your answer.

Having fitted a fair few toughened glass screens in my time I sincerely doubt that pushing too hard on the screen with a clay bar would cause it to shatter. We used to use a rubber mallet on them to get them to sit in correctly whilst pulling the rubber in over the openings with a cord. You wouldn't dare do it with a laminated screen though!

I'd also think it unusual that it could be caused by a concentration of heat from a buffing wheel. If you think about it, every time you put the demister onto the screen it would heat unevenly and shatter if that were the case. Same goes with having the sun on half your screen and the other half shaded by a building or other object.

I'm wondering if it may just be a coincidence that both times your screen has shattered it has been (coincidently) after using the clay bar.

From my experience with screens (and especially toughened glass ones) I'm wonder if you considered how well the replacement screen was fitted. Did you replace it yourself or have it done by someone else? The reason I ask is that I have a possible theory behind what's happened in your situation.

As you are obviously well aware, those tiny glass fragments get absolutely everywhere when the screen shatters. When reusing an old rubber it needs to be examined and cleaned very thoroughly to ensure there are no fragments remaining in the channel where the windscreen glass sits. If you miss a tiny bit it will rub against the toughened glass until it scratches the tempered glass and then BANG! She's gone.

I'm thinking that your first screen popped for whatever reason, maybe a small stone you didn't see or hear, and then the second one shattered due to the reasons I've outlined.

Just a thought,

Russ.

[Dave_Obsession]

Just bizarre!
There is no way that using a claybar on your windscreen could cause it to fail.

Claybars are not abrasive, they are using to pull contamination off the surface. So the thickness of the windscreen is not being altered through the use of a claybar. Especially the Meguiar's one you've used - it's quite mild in terms of it's aggressiveness.

I can assure you the answer as to why the windscreen(s) failed lies elsewhere...

But definitely a strange one!

[Poorboy_racer]

Thanks for the suggestion Ozpacman. I did replace the windscreen on all occasions myself. Its not that hard on a Mini just need a special tool to get the sealing strip in. First replacement screen about two years ago was shortly after the car had been resprayed so a new rubber strip and sealing strip was used. I know that the rubber strip was siliconed to the car but the glass was not in siliconed into it. I very much doubt that I would have left any glass shards in the rubber strip. I know that when I put my latest screen in on Saturday. I got all the old silicon and glass that was stuck to it out of the channel. I guess something could have got in the channel when fitting the new screen but I doupt it and it’s a big coincidence that they both shattered immediately after using the clay bar. I put a post on the Ausmini web site to see if its happened to any other Minis. Nothing yet apart from someone suggesting that the clay could get into micro scratches and chips in the screen then expand due to heat causing the screen to shatter. But that sounds highly unlikely to me.

[IceValk85]

got a third screen and that clay bar to try once more?

3rd times a charm as they say...

Ice

[Shonky.]

as I understand it the screen is not laminated if it shatters like that.

Just saying if you are too explain it elsewhere to someone it is toughened

Semantics I know, but if the issue is chemical (or mechanical) and someone has the answer the type of glass may be important.

Not quick changes in temperature is it? Hot, then cold?

Good luck

[pottery beige]

stop scabbing out re using old windscreens.. problem solvered....

[Poorboy_racer]

I now have a definitive answer from the Mini Web site which makes sense:
It's because it is a toughened (not laminated) screen. Used on all Oz Minis except Cooper S (and maybe GT) which were laminated.
The surface of the glass in a toughened screen is in compression, when you clay bar it the surface stress is released, so tinkle tinkle.
You shouldn't even polish marks out of these screens with glass polish I've been told.
Get a new laminated one...

[Poorboy_racer]

Hang on a sec... Is your name Mark?
If it is, I think we may know each other...

Yes my name is Mark how do you know me?

[Poorboy_racer]

Ahhh noticed the plate on your ute build.
Joe how are you mate?
Nice car mate!

[Pepscobra]

Originally Posted by Poorboy_racer

I now have a definitive answer from the Mini Web site which makes sense:
It's because it is a toughened (not laminated) screen. Used on all Oz Minis except Cooper S (and maybe GT) which were laminated.
The surface of the glass in a toughened screen is in compression, when you clay bar it the surface stress is released, so tinkle tinkle.
You shouldn't even polish marks out of these screens with glass polish I've been told.
Get a new laminated one...

Well, wadaya know...!
kinda makes perfect sense... only thing is that the clay bar isnt really abrasive and shouldnt be removing any glass material from the surface.
But I guess it's the most plausible explaination under the circumstances.
Bet that was doing your head in.