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Old 04-28-2019, 08:57 PM   #1
Ian in Mississauga
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Default Window glass

Hi all, my local club had a vehicle inspection day today and we were unsure how to distinguish between tempered glass and plate glass. Laminated glass was no problem of course. Any suggestions?
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Old 04-29-2019, 10:35 AM   #2
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Default Re: Window glass

https://www.google.com/search?q=how+...hrome&ie=UTF-8
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Old 04-30-2019, 06:59 AM   #3
marty in Ohio
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Default Re: Window glass

Interesting youtube, but is there a way to tell the difference without smashing the windows in your car?
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Old 04-30-2019, 07:02 AM   #4
77Birdman
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Default Re: Window glass

I know for residential use, tempered glass always has a small stamp/mark on it near a corner for identification, no idea if this is done in the auto industry as well.
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Old 04-30-2019, 10:58 AM   #5
duke36
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Default Re: Window glass

Tempered edges should be very smooth to touch and hopefully marked but not always. Replacement glass cut to size can't be tempered first and then cut afterwards.
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Old 05-01-2019, 07:28 AM   #6
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Default Re: Window glass

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Hope this helps it does work well, tricky part may be finding some polarized sheets/film:

This is a direct quote from a good old post on the Aquatic Plants Digest:

Take two photographic polarizing filters, and Sandwich them together. Rotate one of the filters. Light transmitted through the filters will fade from lighter to completely blacked out as the planes of the polarized material crosses through each other's axis. Now, try the same thing with the piece of glass sandwiched between the two filters, and rotate one of the filters. If the glass is untempered, the light transmitted through the filters will act the same way, fading from lighter to blacked out. If the glass IS tempered, an interesting phenomena will occur: as the filters are rotated, a black cross will form through the filters. It's an unmistakable sign: if the cross is there, the glass is tempered.

fyi, I believe the phenomena described with the polarizing filters occurs due to the way in which the glass is cooled at the final stage of the tempering process. After the glass is heated it is air cooled by many jets of air that are moved either in a linear back and forth motion or a circular motion. The first results in noticeable linear lines in the glass when viewed at the right angle and the latter results in an evenly spaced disc pattern.
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Old 05-01-2019, 08:56 AM   #7
jhowes
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Default Re: Window glass

The use of the polarized films, or sometimes glass rings, is used in industry to look for stress in the glass being examined. The stress will disorenate the lines of polarized light coming through the glass being examined so that the 90 degree polarized lens on the opposite side of the glass cannot shut it out. Hence some amount of light will come through the second lenze.
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Old 05-01-2019, 08:59 AM   #8
jhowes
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Default Re: Window glass

What I don't understand in this discussion is what is the safety glass? Is it tempered or some other process used?
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Old 05-02-2019, 05:55 AM   #9
marty in Ohio
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Default Re: Window glass

As I understand, tempered glass is hardened and will break into many, many small pieces and not large shards that will injure. Safety glass is two pieces of glass with a plastic or glue sandwiched between that will hold the window together if broken. My question is, if there is a way to tell the difference?
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Old 05-02-2019, 06:32 AM   #10
BRENT in 10-uh-C
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Default Re: Window glass

Phred, I would consider you the glass expert here since you own a glass shop.


As for tempered glass, I have started using tempered in window glass unless my customer says differently simply because it is safer than safety glass. Maybe it is the company's process but with a pair of cheap sunglasses on, you can look at the tempered glass in the sunlight and it has a series of red-ish/blue-ish dots much like a checkerboard pattern. Also, the edges always seem to be 'frosted' on the tempered whereas the plate glass always seems to be clear.
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