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Window graphics cracking the glass?
Not a job of mine but talking to the owner of our local mini-mart/Post office he mentioned the problems he has with the window graphic for the shop logo.
He’s part of the nationwide ‘key stores’ group but whenever they have put what he calls the big window freeze along his front window, approx 8′ x 8′ with the graphic covering abpout half, the glass subsequently cracks 😮 Anyone else ever come across this? It’s happened to him twice so currently has no vinyl on the window and it’s fine, no crack.
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13 Replies
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quote Lee Ballard:Not a job of mine but talking to the owner of our local mini-mart/Post office he mentioned the problems he has with the window graphic for the shop logo.He’s part of the nationwide ‘key stores’ group but whenever they have put what he calls the big window freeze along his front window, approx 8′ x 8′ with the graphic covering abpout half, the glass subsequently cracks 😮 Anyone else ever come across this? It’s happened to him twice so currently has no vinyl on the window and it’s fine, no crack.
The glaziers are putting the glass too tight in the frame.
I do subcontract signage for a glazier here, and we both make a tidy living repairing glass and resigning it after a sign shop has signed a shop with the pane installed wrong.
The window frame is probably not square and the glass is, the vinyl absorbes heat, the glass being too tight expands when hot, and with nowhere to expand too, it cracks.
The same with windscreens on cars, If you have a stone chip on a windscreen, then put a banner across the screen like a sash type thing, the banner will cause the window to hold heat, and the stone chip will become a crack.
It may just be our heat here, but car dealers do not use a banner sash now if they can avoid it as a result
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Does the graphic have black in it?
I have heard of windows that have large amounts of black on them cracking, whether it’s paint or vinyl.
The sun heats the black up and expands the glass, causing the cracking.
You also have to be careful when heating glass for a winter application for the same reason.
Like Shane sez.
love…..jill -
I thought it may be a glass expansion prob and said this though his glazier assures him it in correctly with expansion room, though I’m not convinced.
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i’ve also heard that when you put window tinting on windows (the buildng not the software) and there is a shadow (like from a tree) at noon or so and it stays long enough on the window it can also crack because of unequal warming up of the glass
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quote dennis:i’ve also heard that when you put window tinting on windows (the buildng not the software) and there is a shadow (like from a tree) at noon or so and it stays long enough on the window it can also crack because of unequal warming up of the glassYup, I was speaking to a tint-film supplier and he recommended sticking to mirror of light tints for large glass areas exposed to the sun. The dark tints must pick up a hell of a heat!
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Hi all,
Typically window film only causes thermal cracking in Georgian Wired glass and laminated glass. This is usually when a Silver 20% VLT is fitted or equivalent / lower VLT film. I’ve rarely heard of it with vinyl though! Unless the glass is very thin and used in a place where theres a large temperature difference on each side or exposed to high outside temperatures.
Is the vinyl on the inside and a dark or metallic colout? Effectivly the glass cracks because the sun shines through the glass (heating it slightly), reflects off the window film / vinyl and heats the glass again. Sometimes, the sunlight then goes on to reflect again off the outer edge of the glass again, back at the film causing total internal reflection. This is what usually makes double glazed units "blow".
I’ll double check with my Dad, but I’m fairly certain this is correct.
Adam
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I agree, as far as im aware this isnt an unusual problem at all, ask any window tinter, as far as im aware, this is really common and they have a unit they use to test the kind of glass they are applying film to as apparently some kinds of glass will crack when coating in film.
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Yes, the units we use are known as a "Sharples Kit" In effect it’s a case full of little gadgets that tell you how thick the glass is, if it’s laminated etc etc….it’s rather smart! Maybe it’d be an idea to get a local tinter to check the glass? (If they have the kit that is)
Adam
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quote Adam McGuire:…….. Effectivly the glass cracks because the sun shines through the glass (heating it slightly), reflects off the window film / vinyl and heats the glass again……Adam
From what little I understand about thermodynamics & thermal radiation, in this instance I’ll dissagree. (no offence) 😕
Get three windows. Leave one blank, put DARK vinyl or very heavy tint on one – front or back, and WHITE/MIRROR on another pane. I guarantee you that the dark one will get hotter and expand / stress the glass more. Why. Because the dark surface is absorbing nearly all the IR (& VL) whereas, the mirror or white surface reflects nearly all of it. The glass absorbs a minimal amount – so minimal it’s not worth bothering about. The clear ‘control’ panel will not have noticably increased in temperature (why your house windows are not hot on a sunny day) If the ‘twice through the glass’ approach was the cause of heating, surely a clear panel would be half of the temperature of a coated one.
Clear glass, by it’s very nature transmits VL very well, and UV & IR fairly well. It’s the IR that’s the problem for our purposes and it’s the COATING that reacts to the light and warms the glass through conduction.
Dave
Well, I believe it anyway…. :lol1: …. and I’m sticking to it!
Edited to fix splling errir
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Lol I understand what you mean, I’ll check with my Dad as he knows all that! You’re probably right and I’m probably wrong! I’ve had a long day! I’m not thinking straight.
Adam
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quote Adam McGuire:………… I’ve had a long day! I’m not thinking straight.
Adam
Same here! ….I’ve not had my lunch yet…or breakfast come to think of it……… does a handful of Bombay mix and a tin of IRN BRU count? 😀
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I agree David 😉 I still want to be on your trivial pursuit team 😀
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quote Shane Drew:I agree David 😉 I still want to be on your trivial pursuit team 😀
LOL, :lol1:
Is there a new version out with the topic "Useless crap that comes in handy maybe once or twice….."
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