black vinyl breaking glass?

[BROWNDOG]

is it possbile? i have a restaurant wanting to cover their windows with black vinyl, but heard that it may attract so much heat as to break the glass,
i cant imagine it getting that hot, but then again what do i know, ive never done it.

 

[HDvinyl]

Yes, possible. Not only black.

 

[joeb]

I've heard of it happening, especially when its full coverage. If you are covering less than 50% of the window you should be good but don't take my word for it.

 

[Billct2]

is it possbile? i have a restaurant wanting to cover their windows with black vinyl, but heard that it may attract so much heat as to break the glass,
i cant imagine it getting that hot, but then again what do i know, ive never done it.

 

[Gino]

It's very possible and many different factors can make it go in lotsa outcomes. The way they're facing, how much of the window is being covered, the overall size of each pane, kinda of glass, the method of glass installation... even the quality of the vinyl can have a part in it.

We did a restaurant about 25 years ago with double-sided gold leaf vinyl cut in reverse on the glass first, then about a 30"' high piece of black along the entire length of all the windows. The floor level was above the pavement level and the owner didn't want all the legs showing along the windows from outside.... for various reasons. The windows were 6' tall and 8' wide. A total of I think 8 windows. They just removed the vinyl about 2 or 3 years ago and it was in perfect shape and so was the lettering. It went from being a restaurant to a flower shop, so they wanted the flowers to show. Anyway, never had anything break, but I believe because we didn't cover a large portion of each window, although it was still a lot overall.

 

[bannertime]

Interesting. I'm in Texas and have never heard nor seen it. I've covered many doors with solid cut vinyl. Facing all directions. Some of those doors may have had glass nearly 50 years old. Will ask my glass guys if they've seen it, but I doubt you need to worry about it. Just make sure you mention that you can't be held liable because you could never know the condition their glass is in or what people are doing to it.

 

[oldgoatroper]

covering the entire window would likely be safer... the problem occurs when the sun strikes the vinyl and heats up the glass underneath and if the heating is rapid enough and the heat cannot dissipate evenly into the uncovered cooler glass, the glass will get stressed and shatter. That's why it breaks -- temperature differential, not absolute temperature. Which is also why covering an entire piece of glass is likely not to break it, unless there is shadow involved. This happened many years ago in Calgary on a Safeway store. New large red letters on the inside of large overhead storefront windows -- winter temps outside, sun comes over the neighbouring building and windows started shattering... they thought at first there was a shooter in the area...

 

[equippaint]

Usually the glass breaks from an internal flaw, bad annealing process where it doesn't cool evenly or poor installation that causes it to bind especially with tempered. Like old goat said (have to lol typing that) its the rapid, uneven heating that poses the problem and not the heat itself within reason. The anecdotal evidence of decals breaking the windows Id venture to say were actually caused by problems mentioned above and possibly aggravated by the vinyl but not caused solely from it. Vinyl may raise the surface temperature a little but it cant hold any significant amount of heat. If it could, car doors with black wraps would be all sorts of warped.

 

[Chasez]

Everyone does have good valid points here and there. There are a lot of contributing factors (ie. poor glass quality, sealed unit, chipped glass behind window stops) as to why it would crack the glass but yes covering all or partial windows in black vinyl can cause thermal breakage of the glass. Typically if it is a sealed unit (2 pieces of glass sealed together - not laminated glass) it will for sure break. We just quoted to replace some here where someone put black vinyl on the bottom portion of a window of a restaurant (sealed unit) on the exterior face, facing west and one facing south and both cracked within a month. We specialize in 3M window film and deal with this on a daily basis (tints are no different than vinyls) and is a major contributor as to what films can be applied.

You would be safer to apply a white out material which will block the view/light coming through the window but will eliminate the biggest portion of having a thermal crack.

Chaz

 

[rjssigns]

Happens with IG(insulated glass) panels. There are calcs used by window tinters to make sure they don't have issues. A high school not far from me went with the low bid tinter after my buddy the pro said what you want to do won't work. Long story short most of the windows that were tinted shattered. My buddy had a good laugh. Perfect example of not knowing the scope of the job and all the variables.

I see vinyl and tint as the same. YMMV

 

[Chasez]

Happens with IG(insulated glass) panels. There are calcs used by window tinters to make sure they don't have issues. A high school not far from me went with the low bid tinter after my buddy the pro said what you want to do won't work. Long story short most of the windows that were tinted shattered. My buddy had a good laugh. Perfect example of not knowing the scope of the job and all the variables.

I see vinyl and tint as the same. YMMV

It is true, you calculate the film stress factors and the thermal stress factors which will give you a total PSI and you compare it to the MAX PSI of the glass. There are tons of variables such as shading, type of glass, thickness of glass, shape of glass to name a few to calculate the factors to figure out your PSI. If you go over your MAX PSI you will most definitely break some glass.

Chaz

 

[bob]

I've heard of it happening, especially when its full coverage. If you are covering less than 50% of the window you should be good but don't take my word for it.

You've actually heard of it, wow. And I've actually seen a quarter appear out of the nose of a small boy.

Glass is some pretty tough stuff and a little heat absorbed by some vinyl stuck to it is not likely to cause it to break. If it does then I would strongly suspect that there was something wrong with the glass.

 

[oldgoatroper]

You've actually heard of it, wow. And I've actually seen a quarter appear out of the nose of a small boy.

Glass is some pretty tough stuff and a little heat absorbed by some vinyl stuck to it is not likely to cause it to break. If it does then I would strongly suspect that there was something wrong with the glass.

Heat doesn't break glass, in fact glass can withstand any amount of heat. It's the by-product of applied warmth (absorbing heat from a heat-collecting material in contact with the glass) which is expansion -- namely uneven expansion or expansion beyond it's container (frame).

And it doesn't even need to be a lot of heat to expand a pane of glass beyond the limits of say, a tight-fitting frame in the case of compete coverage or tint.

And in the case of just lettering -- well, imagine a big 4' letter S on a large pane. and the sun comes around the corner on a cool day... what's going to happen? Well, the glass covered by the vinyl in the shape of an S is suddenly going to start absorbing heat and expanding where the glass surrounding the letter is not absorbing direct heat from the sun and not expanding. Once a crtitical temperature differential is reached that pane is going to shatter from the uneven strain. And the temperature of the glass in its warmest spot need not even be that hot. Like, say, on a cold winter day in Calgary.

We all know better than to use a heat gun on glass -- its the same principle.

 

[ams]

Yes and it happened to me before I learned about it. Oracal says to leave a 1/2" gap around the whole window for safety, however we do 1". Using a high quality vinyl helps too.

 

[astro8]

I've had one window break, years ago, but it was with black paint, not vinyl. It was a band along the top of a window and broke an hour after I finished it. I wouldn't have believed it unless I saw it with my own eyes.

 

[boxerbay]

weve done hundreds of liquor store windows and never had any break because of the vinyl.

 

[equippaint]

I still dont see how vinyl or tint would break glass. It wouldnt make a difference if it was IG or not. The outside pane of IG glass would still absorb the heat evenly on that panel. The middle is just a thermal break but the individual glass by itself will still absorb heat evenly, it just doesnt project it as much to the other pane.
In curtain wall construction, mechanical rooms as well well as other areas that need to be hidden, there is a solid block out opaque coating on the glass edge to edge. Glass in cars and equipment has blackout coatings too in partial areas. Look at the frameless windows in buses, they have black blockouts that hide the bus frame. I do understand not using a heat gun or torch on glass since it is a rapid concentrated heat that the glass can not distribute fast enough which causes uneven heating and breaks it. With vinyl, it will be a slow warmup and whether it is partial or complete, the glass itself will evenly distribute the heat faster than the partial area can warm a concentrated section.

 

[oldgoatroper]

I still dont see how vinyl or tint would break glass. It wouldnt make a difference if it was IG or not. The outside pane of IG glass would still absorb the heat evenly on that panel. The middle is just a thermal break but the individual glass by itself will still absorb heat evenly, it just doesnt project it as much to the other pane.
In curtain wall construction, mechanical rooms as well well as other areas that need to be hidden, there is a solid block out opaque coating on the glass edge to edge. Glass in cars and equipment has blackout coatings too in partial areas. Look at the frameless windows in buses, they have black blockouts that hide the bus frame. I do understand not using a heat gun or torch on glass since it is a rapid concentrated heat that the glass can not distribute fast enough which causes uneven heating and breaks it. With vinyl, it will be a slow warmup and whether it is partial or complete, the glass itself will evenly distribute the heat faster than the partial area can warm a concentrated section.

If glass is heated, it will expand... even if the expansion is slow and even... but when glass expands beyond the limits of the frame that it's in, it will break.

I would imagine that most windows are designed/engineered for some expansion -- but covering a window with a film (vinyl, paint, whatever) that will absorb more heat that spec'd causing more expansion than expected will eventually bite someone in the ass.

And just musing here, i would imagine this would occur mostly in aluminum or steel framed windows, as I would think a wood frame might be soft or flexible enough to absorb some extra expansion -- but just speculating on that point.

So, just to be clear -- there are two ways heat expansion can break a window --
1) uneven expansion and
2) expansion beyond the limits of a frame

 

[bob]

Heat doesn't break glass, in fact glass can withstand any amount of heat. It's the by-product of applied warmth (absorbing heat from a heat-collecting material in contact with the glass) which is expansion -- especially uneven expansion or expansion beyond it's container (frame).

And it doesn't even need to be a lot of heat to expand a pane of glass beyond the limits of say, a tight-fitting frame in the case of compete coverage or tint.

And in the case of just lettering -- well, imagine a big 4' letter S on a large pane. and the sun comes around the corner on a cool day... what's going to happen? Well, the glass covered by the vinyl in the shape of an S is suddenly going to start absorbing heat and expanding where the glass surrounding the letter is not absorbing direct heat from the sun and not expanding. Once a crtitical temperature differential is reached that pane is going to shatter from the uneven strain. And the temperature of the glass in its warmest spot need not even be that hot. Like, say, on a cold winter day in Calgary.

We all know better than to use a heat gun on glass -- its the same principle.

Well then Dr. Science, according to my sources plate glass will expand somewhere around 0.0008" per linear inch per 100 degrees temperature rise. Not the rate of expansion that leads to shattering one should think.

Has anyone, anyone at all, ever actually hands on, not tales from a friend of a friend, broken or witnessed the breaking of a pane a pane of glass via this type of heating? Not that you couldn't be putting out the truth, the whole truth, and nothing but the truth but this certainly smells of urban legend.

Heat doesn't break glass, in fact glass can withstand any amount of heat. It's the by-product of applied warmth (absorbing heat from a heat-collecting material in contact with the glass) which is expansion -- namely uneven expansion or expansion beyond it's container (frame).

And it doesn't even need to be a lot of heat to expand a pane of glass beyond the limits of say, a tight-fitting frame in the case of compete coverage or tint.

And in the case of just lettering -- well, imagine a big 4' letter S on a large pane. and the sun comes around the corner on a cool day... what's going to happen? Well, the glass covered by the vinyl in the shape of an S is suddenly going to start absorbing heat and expanding where the glass surrounding the letter is not absorbing direct heat from the sun and not expanding. Once a crtitical temperature differential is reached that pane is going to shatter from the uneven strain. And the temperature of the glass in its warmest spot need not even be that hot. Like, say, on a cold winter day in Calgary.

We all know better than to use a heat gun on glass -- its the same principle.

A heat gun [or a torch] most certainly is not the same principle.

Before you pose that a light absorbing coating over a glass panel can cause the glass to break because of expansion you might want to familiarize yourself with the coefficient of thermal expansion for glass, which compared to other materials is quite low. If memory serves plain old plate glass expands a few ten-thousandths of an inch per foot per 100 degrees of temperature. Hardly the stuff of shattered glass.

There may be something more to coating just a portion of the glass. Then there would be uneven heating that might do something. Or it might not. One would have to compare the light absorption properties of the coating to that of the glass itself.

 

[oldgoatroper]

Well then Dr. Science, according to my sources plate glass will expand somewhere around 0.0008" per linear inch per 100 degrees temperature rise. Not the rate of expansion that leads to shattering one should think.

Has anyone, anyone at all, ever actually hands on, not tales from a friend of a friend, broken or witnessed the breaking of a pane a pane of glass via this type of heating? Not that you couldn't be putting out the truth, the whole truth, and nothing but the truth but this certainly smells of urban legend.


A heat gun [or a torch] most certainly is not the same principle.

Before you pose that a light absorbing coating over a glass panel can cause the glass to break because of expansion you might want to familiarize yourself with the coefficient of thermal expansion for glass, which compared to other materials is quite low. If memory serves plain old plate glass expands a few ten-thousandths of an inch per foot per 100 degrees of temperature. Hardly the stuff of shattered glass.

There may be something more to coating just a portion of the glass. Then there would be uneven heating that might do something. Or it might not. One would have to compare the light absorption properties of the coating to that of the glass itself.

doesn't matter how much or how little the expansion is... it only matters if the expansion is uneven enough to cause sufficient stress to cause breakage. Remember, glass is very brittle, relatively speaking and expansion, even a tiny bit, can induce some very powerful forces.

Same with reaching the limits of a frame - it won't matter if the expansion is "only" a tiny bit more. That tiny bit is going to be enough.