Thermal Pane ??

Rick Sacks · Post by **Rick Sacks** » Tue Dec 07, 2004 5:43 pm

I did a gold job on some dual glazed panels that look like there is perhaps 3/4" between them. I wonder if I painted a dark panel behind the gold would it heat up the air between the glasses to where it could break?

Dan Seese · Post by **Dan Seese** » Tue Dec 07, 2004 9:57 pm

Rick,
Iâ€™m not sure how much I can help in answering your question since Iâ€™m wrestling with a similar situation.
Here are some factors to consider, from my limited understanding:
1. A dark panel is going to absorb a lot of heat. If the panel goes from edge to edge, have it stop about Â½â€ from each side. That will decrease your chances of breakage considerably. (I have a storefront with a bank of south-facing 48â€ wide windows. Each window has light-colored copy contained within a BLACK 15â€ high band across the bottom of the glass. The graphics are all vinyl, applied to the 4th surface, i.e. on the inside surface of double-paned glass. I cropped the black band about Â½â€ from each side and have had no problems.)
2. An insulated unit like you describe should actually help since the double pane will insulate the inside window somewhat from the outside temperature.
3. If the glass is tempered, it is much less likely to break from temperature variations within the pane.

In a sense, this is the blind leading the blind. Iâ€™m going to piggyback (hijack?) your post with a question of my own.
I have a south-facing glass transom that Iâ€™ll be doing some work on. It will have glue chipping, gold leaf, burgundy drop shadows and a burgundy band across the bottom of the glass. Iâ€™m concerned, not only with breakage, but also with colors fading. Iâ€™m considering doing an insulated unit with tempered glass on the inside to insure against breakage (after I chip it) and either Low-E glass or laminated glass on the outside. I hear that laminated glass actually cuts UV light considerably because of the resin core.
If anyone has any advice regarding this and regarding Ricks situation, we would appreciate it.
Rick, I hope I didnâ€™t smother your question with my verbose response. I was about to start a thread to get any thoughts on my job and saw yours with a similar concern so I chimed in here.
Dan

Rick Sacks · Post by **Rick Sacks** » Thu Dec 09, 2004 8:03 am

Dan, I just wonder which direction to be thinking.....will I increase or decrease the chances of incurring heat damage?

Dan Seese · Post by **Dan Seese** » Thu Dec 09, 2004 10:39 am

Rick,
Sorry that my explanation was as clear as mud. Like I said, Iâ€™m trying to figure this out myself.
If I understand correctly, putting a dark panel on the glass does increase your chance of breakage. However, if your dark panel does not cover the entire width of the glass and there is a gap on either side, the expansion of the glass due to heat transfer if mitigated by that gap.
You might check to see if there is a tempered imprint on the corner of the glass. If the glass is tempered, it will be a lot stronger and will resist breakage much better than regular annealed glass.
The heat trap you are asking about is a valid concern and I think if you keep in mind the 2 above points (size of the painted panel & tempered glass) you should be ok. Sign painters have been painting panels on glass for years. I have a number of panels on glass with no problems.
(I did have a window break shortly after putting graphics on it a year or 2 ago, but I think we determined that it wasnâ€™t due to the graphics.)
You might check this link which gives some technical explanations of the thermal stress, including your concern about heat trap causes by glass decoration.
www.pilkington.com/resources/ ats123swthermalstress200203.pdf

Last but not least, please note this disclaimer:
The information contained herein is somewhat dubious since the author himself doesnâ€™t have a clue and is trying to figure it out himself.
Hey, if anyone else can help us out, please do so.
Thanks

Post by **Mike Jackson** » Thu Dec 09, 2004 11:35 am

I will just throw this out there.

Back when I was still in college, I had to paint some lettering on a tavern window near campus. Interestingly, the 6' x 8' panes of glass were painted only about 2/3 up with bright red paint, with clear glass on the top 1/3. This was to let light in during the day and let passersby see the bar lights at night, but not allow people to actually see anything in the bar. I am sure there would be something somewhere written about this topic...maybe even in the old LeBlanc book? Apparently red resists absorbing too much heat, unlike black.

Someone else here might know where to find the technical documents on this subject, but they have to exist.

Also, I don't believe water size needs to be "hot" to work. I don't even think it has to be warmâ€”just fresh. I don't think you should have to worry about breaking a cold piece of glass using warm size.

Mike

Rick Sacks · Post by **Rick Sacks** » Fri Dec 10, 2004 9:04 pm

I understand the importance of stop lines on the glass for expansion around the edges. I remember also breaking a piece of glass as an apprentice where I had a large dark panel in the sun. What I'm asking is if the gap between the two panes will get hotter and act as an oven to increase the possibility of breaking if I paint a dark grey marbled panel behind the gold?

Bill Cosharek · Post by **Bill Cosharek** » Sat Dec 11, 2004 11:58 am

So, the question is: "Does the area between the glass panes (which is supposed to be a vacuum) get extremely hot or cold?"

I thought the purpose of having thermal panes was to reduce changes in temperature thus retaining indoor temps alap. If extreme temps occur, then the seal might be broken.

So, the question should be: "Does a vacuumed area normally get hot or cold, or should there be no change?" Maybe a window-expert would know the answer.

I just re-phrased the question, but don't have an answer yet.

Terry Whynott · Post by **Terry Whynott** » Sat Dec 11, 2004 8:51 pm

Rick, that gap will heat up with something dark on the glass.

It's been my experience with commercial window film that any film installed had to be reflective to reflect the sun's heat away. If a smoked film was installed, the heat build up between the panes would cause it to break.

I have heard of panels of vinyl being installed on glass and causing it to break as well. You are right to be concerned.

Post by **Ron Percell** » Thu Dec 16, 2004 10:18 am

Hi Rick,
Double and triple-paned windows are being filled with an insulating gas to prevent heat transfer through the windows. The most commonly used gases are Argon and/or Krypton.

I'd think your pretty save on these types of windows, even it they're not filled with rare gases.

Thermal Pane ??

Thermal Pane ??

Blind leading the blind . . .