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Anonymous Poster

Tempered Laminated Glass - Distortion Specification?

02/19/2009 7:33 AM

Hello, I'm Looking for a specification for distortion for tempered laminated glass. all specs (ASTM and GANA) I have found indicate there are no architechual or industrial standards that address a quantifiable measurement of distortion of tempaered glass after lamination. I understand measuring millidiopters for roller wave on heat treated glass before lamination but can only find suggestions of some subjective measurements after lamination. Just curious if anyone that has or knows of an objective measurement of HT glass distortion after lamination. I have been told by glass maufactures once laminated they will not provide any specification for the limits of distortion. I do not have any trouble getting an exchange or credit for lites that have noticable distortion but would perfer to have a measureable standard to refer to. Thanks for any response.
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ozzb
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#1

Re: Laminated glass distortion

02/19/2009 7:53 AM

I don't think they have looked that far. Most companies are still trying to produce an window or door that will take the high impact test. Most have not looked at the distortion that comes with lamination. As I have been told any distortion or flaw in the glass that can't be seen from ten feet is acceptable. Then again each of of us is different. What one can't see another may because of better eye sight. It is also hard to argue with the customer if you want to get payed.

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tom@windoor
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#2
In reply to #1

Re: Laminated glass distortion

02/19/2009 9:40 AM

Thanks for the response. This particular product has performed well in the large and small missile impact tests. The ten foot rule of thumb is okay. unfortunately the complaints I see are customers looking at adjacent buildings and seeing some squiggle in the eccentric lines say in balconies, railings , etc. through the glass - particularly at the edge of the glass where the roller wave is more accentuated. I sometimes can catch this distortion in reflected light when the glass is horizontal. Measure the millidiopters and find the wave exceeds the manufacturer's spec for the flat heat treated glass. I'm thinking customer education on what they may have to give up when going to high performance glass is in order.

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ozzb
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#3
In reply to #2

Re: Laminated glass distortion

02/19/2009 12:41 PM

You sure you are not seeing the quench marks on the tempered glass. In the right light and at the right angle they can be quite noticeable.

We also have used laminated glass as windshields on autos for years with no noticeable distortion. Of course we don't look thru the perimeters of the windshields.

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tom@windoor
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#4
In reply to #3

Re: Laminated glass distortion

02/19/2009 1:48 PM

I believe you are right about the quench marks which seem to just add to the problem. I call it a problem only because a small number of customers have decided it is a problem.

I find myself now looking at every piece of installed glass where ever I'm at and now see some distortion usually slight but in some cases terrific. It seems the brain adjusts for us and ignores the distortion unless you are actually looking for it.

I don't call it a problem unless the angle is accute. Say 90 +/- 30 degrees would be acceptable.

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Anonymous Poster
#6
In reply to #4

Re: Laminated glass distortion

06/23/2009 2:17 AM

Thanks for your method but a method may fail with large glass, which are difficult to measure the rise in
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tom@windoor
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#5

Re: Tempered Laminated Glass - Distortion Specification?

04/15/2009 8:12 AM
Re: Tempered Laminated Glass - Distortion Specification?
Update - for general information

I have recently experimented with measuring distortion in Laminated and insulated glass with a line laser (using a green 532 nm laser @ 5 mw). First I ground and polished a 12X12 inch laminated HT glass sample on one side selecting areas to simulate worst case sag, about .003-005" between rollers sometimes the result of the HT process. Secondly mounted the line laser set 20 feet from a white board and then marking a reference vertical line in line with the laser line on a white board with no glass. lastly moved the sample glass mounted in a fixture perpendicular through the same line. Glass set 10 feet from board and 10 feet from laser. Viewing the laser line you will see the contrasting distorted line. Furthermore, calculating the Millidiopters of the actual polished area to the reference line I can see it is reasonable to establish horizontal measurements or hash lines on the reference mark that would indicate the depth of the cup or concave area in the glass.

If anyone out there has worked on this approach please let me know what your findings and/or conclusions are.

Thanks - Still working the issue

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