Can Thermal fracturing Occur with external application?

December 11, 2007

This job has been carried out by a competitor of ours - I must confess I regarded them as knowledgeable.

Has anyone any experience of MMM film fitted externally causing thermal cracking. I am aware that a lot of factors have to be taken into account such as glass type,thickness and TSAR of film.

These are big panes of thick glass maybe 38mil dimensions around 3mtrs by 2mtr. They are in the sun pretty much all day apart from the bottom half metre. The film is doing a pretty poor job of reducing glare and has quite a high VLT level so am guessing the TSAR is not that high. A lot of the classic signs.

I know the owner quite well and when asked the question my instant reaction was thermal cracking caused by the window film. I have to go back there tomorrow with some kit to measure what I can so I can give him some help in getting compensation from this window film company.

I know some flat glass info but Auto is my forte :lol6 . I do have all the measuring meters etc is there anything you "top boffin" flat glass gurus can advise me to look for or measure to help this guy out.

Many thanks

:lol6

blade · December 11, 2007

my initial thought is that there was already some kind of blem or chip in the glass under the framing. once there was added heat absorption it caused the chip to grow.

December 11, 2007

Thanks for the reply blade.

We have 5 windows cracked building 6-7 year old, tint job a few months old if that.

December 11, 2007

Is the external film a silver or grey?

December 11, 2007

Is the external film a silver or grey?

Thanks for the interest BB.

I did not look at the outside due to access issues and because I did not want to start slating someone elses work. From inside it did not have the blueish hue you normally associate with silver, it did have a v light silver appearance almost stainless steel. Probaby gonna be silver.

I'd imagine they would put the exact film spec on the invoice and I'll find that out tmrw. Whilst chap says its MMM it might be something else and sold as MMM.

Would it be worthwhile taking window temperature at its hottest and coldest spots during the warmest part of the day? Is there any formula for risk assesment or do most installers just rely on their film supplier saying yep it'll be OK.

December 11, 2007

I've never heard of any probs with external silver 20, but some of the greys I have heard of it. Bottom line is that the film "contributed" to the breakage most likely. The only way you can tell for sure is pull film off one window and test the temps on the one filmed vs the one not filmed. Soon you'll see the reason.

December 11, 2007

I've never heard of any probs with external silver 20, but some of the greys I have heard of it. Bottom line is that the film "contributed" to the breakage most likely. The only way you can tell for sure is pull film off one window and test the temps on the one filmed vs the one not filmed. Soon you'll see the reason.

Good idea - had not thought of that. May sound like a silly question but would it be best to measure the temperature on the inside or outside of the glass.? I suppose both wouldn't hurt.

This looks like being a good opportunity for me to learn first hand. This does not happen every day :lol6

suntint · December 11, 2007

In the USA at least, the only exterior compatible MMM window film I'm aware of is silver. Silver is thought to be relatively low risk, compared to other films, of leading to thermal fracture (it reflects much of the heat away instead of absorbing it). I would not have expected problems installing silver film to the exterior of even large windows like this. I would not have hesitated in doing so.

If it's not a silver film, but something like a grey, then the chances of a problem is greater (although the number of fractures they've had is surprising). If it is something like a grey the other dealer may have installed a film not meant for the exterior (not a good idea - it will have a short lifetime), or an exterior compatible film which is not MMM.

December 11, 2007

In the USA at least, the only exterior compatible MMM window film I'm aware of is silver. Silver is thought to be relatively low risk, compared to other films, of leading to thermal fracture (it reflects much of the heat away instead of absorbing it). I would not have expected problems installing silver film to the exterior of even large windows like this. I would not have hesitated in doing so.
If it's not a silver film, but something like a grey, then the chances of a problem is greater (although the number of fractures they've had is surprising). If it is something like a grey the other dealer may have installed a film not meant for the exterior (not a good idea - it will have a short lifetime), or an exterior compatible film which is not MMM.

Thanks Suntint

I agree. Unless this is a new mmm prod. Then maybe thickness of glass is factor or how the glass was originally installed. Either way as BB say the film has contributed and the best way to check by how much is to de-tint one and measure the temp difference.

December 12, 2007

Good idea - had not thought of that. May sound like a silly question but would it be best to measure the temperature on the inside or outside of the glass.? I suppose both wouldn't hurt.
This looks like being a good opportunity for me to learn first hand. This does not happen every day