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Old 09-28-2012, 03:31 AM   #1
Craig Lewis
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Default Unsafe safetyglass.

A recent thread prompted me to type out these few notes on safety glass for anyone who may not be familiar with modern practices and current safety standards.

I'd like to suggest there is nothing "safe" about the practice of using Laminated safety glass throughout an entire motor vehicle.


#1) Laminated safety glass = 2 individual panes of plate glass glued together by a .030" thick layer of strong, stretchy, clear vinyl
...like a cheese sandwich

For the last 50 years, 99.9% of the vehicles you see have been manufactured with only a single piece of laminated safety glass per vehicle
....this is the windshield.

In the event of collision, the occupants of a vehicle are deemed to be safest inside that vehicle till it skids or tumbles to a rest.
Laminated windshield's do an admirable job of resisting penetration, in fact although they've messed a few faces...that strong vinyl core really holds together and keeps you off the street.
...gosh I think one would need a 4 foot long 2x4, taking several hard swings, to punch a big hole through a laminated windshield...


#2) Tempered safety glass = plate glass which has been heated then rapidly cooled (usually with air). This process makes it super tough, hard & flexible with no visual change whatsoever
...still looks like a hunk of plate glass except now it's toughened.
..it's weakness??..when tapped hard enough with a sharp object, like a rock, hammer or piece of sharp metal, it crumbles into a realatively harmless pile of tiny cubes leaving the entire window opening unobstructed for a safe and swift exit.
Rescuers at an accident scene can simply pick up a rock off the shoulder and delete the tempered glass in one blow to access the occupants.
........Unless of course it's one of the vintage cars out there which feature laminated windshield glass for each and every window in the car.

Now granted in most accidents some windows and doors will usualy operate after the crash...but for the not-so-lucky you still need to exit in a reasonably timely manner...especially with Model A's featuring "laptop" gas tanks......
Remember, if you look around virtually every vehicle on the road has the back & side windows made of tempered safety glass...for a good reason.

Tempered safety glass can be ordered at most local autoglass shops.
If you want a cheaper price .... do the time consuming (but easy) part yourself and bring them an exact cardboard pattern of the size window you need made. Turnaround time can be a week or two as the pattern is sent out and a truck generally drops off the finished product.
P.S.You can even order it with a pencil-polished edge where your arm rests, just like the original plate glass had!

For the record this isn't a plug for my glass shop...in fact I'm far too busy to take on anymore. There's plenty of glass shop's all over the globe who can provide tempered glass and the cost shouldn't be all that much higher except you have to wait a few days. This is just a stronger, safer & more authentic looking glass choice which makes good sense.

For the "traditionalists" you may consider carrying that 2x4....
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Old 09-28-2012, 05:46 AM   #2
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Default Re: Unsafe safetyglass.

This has been discussed at great length on the Model T forum and I agree; tempered glass for everything except the windshield.

It was mentioned that the VW Beetle in Europe also had a tempered glass windshield with the portion directly in front of the driver left untempered so that forward vision would not be affected in a mishap.

I have assisted with parking at our local museum during our annual old car show. Due to my vantage point, I have spotted many fellow hobbyists that have tempered glass windshields. They're easy to spot because the glass has waves when viewed from the side and is not flat like float glass. I've always wondered if any of these have failed on an open trailer or during a dirt road tour.
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Old 09-28-2012, 05:53 AM   #3
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Default Re: Unsafe safetyglass.

The strength of that tempered glass is amazing. Yesterday I had the misfortune of witnessing a bad car accident. I was stopped at an intersection waiting to turn left and a semi from the opposite direction was making a left turn when a car smashed into the tractor's side. No skid marks, so I wonder if the car driver was distracted and didn't see what was happening. Anyway the truck driver got out and used a 4 way lug wrench to break out a rear door glass to unlock the driver's door. It took several hard swings of the wrench to finally get the window to break.
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Old 09-28-2012, 05:55 AM   #4
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Default Re: Unsafe safetyglass.

The reason cars have had tempered side glass for the last 50 years is that it is easier and cheaper to make tempered CURVED glass than laminate curved glass. About 1965, cars began to use curved side glass, probably to improve interior space without a huge roof area. Also, in the mid 80's, side glass was made much thinner, to save weight, (and probably money), and laminate glass is usually 1/4 inch. Tempered glass is fine, but so is laminate glass, so long as it is not so old that it is de-laminating. Both are better than plate glass, which most models of the model A had in side and rear glass. The model T had plate glass everywhere, and while I have restored a few with original plate glass, I am amazed it lasted 80 years without breaking. I have also replaced a few model A windshields that had plate glass installed at some point. The fact that someone replaced safety plate with plate glass amazes me.
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Old 09-28-2012, 06:05 AM   #5
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Default Re: Unsafe safetyglass.

Is there a downside (i.e: safety reason?) for not considering the use of tempered for windshields too?
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Old 09-28-2012, 06:15 AM   #6
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Default Re: Unsafe safetyglass.

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Quote:
Originally Posted by BRENT in 10-uh-C View Post
Is there a downside (i.e: safety reason?) for not considering the use of tempered for windshields too?
In front end crashes, such as I witnessed yesterday, the laminated glass will keep the driver from flying out the windshield. Plus it would add structural rigidity to the body, where tempered glass would crumble to little pieces, allowing occupants to fly out the front, and make the roof weaker if the car rolled over.
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Old 09-28-2012, 06:39 AM   #7
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Default Re: Unsafe safetyglass.

Quote:
Originally Posted by BRENT in 10-uh-C View Post
Is there a downside (i.e: safety reason?) for not considering the use of tempered for windshields too?
I've never owned a car that did not get at least one highway stone chip in the winshield. That impact which causes an annoying chip on laminated would cause a tempered windscreen to completely disintegrate into rock-salt size pieces that would fly directly in your face.
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Old 09-28-2012, 06:39 AM   #8
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Default Re: Unsafe safetyglass.

Quote:
Originally Posted by Tom Wesenberg View Post
The strength of that tempered glass is amazing. Yesterday I had the misfortune of witnessing a bad car accident. I was stopped at an intersection waiting to turn left and a semi from the opposite direction was making a left turn when a car smashed into the tractor's side. No skid marks, so I wonder if the car driver was distracted and didn't see what was happening. Anyway the truck driver got out and used a 4 way lug wrench to break out a rear door glass to unlock the driver's door. It took several hard swings of the wrench to finally get the window to break.
I personally watched a Dodge Omni roll over on the expressway multiple times and none of the glass broke. They ended up flipping it back over, and had the fluids not started to drain out probably could have driven it home.
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Old 09-28-2012, 07:42 AM   #9
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Default Re: Unsafe safetyglass.

You can beat tempered glass with a hammer and it will most likely not break, but a single shot with a spring loaded center punch will sent it into a million pieces. I carry a punch in a handy place in my truck, just in case.
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Old 09-28-2012, 08:31 AM   #10
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Default Re: Unsafe safetyglass.

My mother has a 2002 Volvo wagon, and the side windows are all of laminated glass. You can see the lamination across the top edge. And they are original: they have the Volvo bug etched on them. I was surprised to see that- I have never seen another modern car without tempered side windows.

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Last edited by Doug in NJ; 09-28-2012 at 09:01 AM. Reason: typo
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Old 09-28-2012, 09:59 AM   #11
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Default Re: Unsafe safetyglass.

Problem with laminated glass when struck by the human body in a sudden stop (ie- collision) is that the glass does break and shard as the skull of the occupants strikes it. The vinyl laminate keeps the glass adhered to it well as the laminate stretches, allowing gaps in the glass. Once the movement has stopped, you have a skull pressed deep into the vinyl with shards of glass broken apart, and pointed toward the point of impact, currently occupied by a human skull. As the skull begins to retreat back into the front seats, those shards of glass are forced into the skin, eyes, and other human tissues being pulled away from the vinyl. That is why people that hit laminated windshields have so much glass impregnated into them.

If you hit a tempered windshield, the glass nuggets head outward, away from the human skull and attached tissues.

For windshields, I suspect tempered glass is safest.

My Model A has laminated glass all the way around. Not ultra fond of that, but that is what I got. If I ever had to get out of the car in an emergency, considering what the top of made of, I will simply stand up! Those of you with an all-steel cab pickup might not want to try that.
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Old 09-28-2012, 10:08 AM   #12
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Default Re: Unsafe safetyglass.

Quote:
Originally Posted by Tom Wesenberg View Post
In front end crashes, such as I witnessed yesterday, the laminated glass will keep the driver from flying out the windshield.
Isn't this what seat belts are for?
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Old 09-28-2012, 10:24 AM   #13
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Default Re: Unsafe safetyglass.

I don't know if I would want to stand up through the roof of my SW Fordor. I think I would be restrained by the wire mesh in the roof. Then there's that annoying steel B-pillar cross brace inside the roof.

Isn't it funny how in the Untouchables movie, that brace was missing when Frank Nitty fell off the roof and into the sedan parked outside the courthouse?

In July my son was hit by a deer in northern Michigan. He didn't hit the deer, the deer ran out and hit him just in front of the door. When the deer slid over the fender and onto the hood, he shattered the windshield. If it would have been tempered glass, the deer would have been in his chest. While the windshield was shattered and bellied in, the deer didn't make it inside the car.

After the accident, I asked the DNR to move the deer crossing a mile down the road to the straightaway where there are less trees. I think it would safer if they crossed there.
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Old 09-28-2012, 11:10 AM   #14
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Default Re: Unsafe safetyglass.

....well occifer I wanted to keep driving straight down the road, but that sign said No, U turn here!
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Old 09-28-2012, 12:10 PM   #15
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Default Re: Unsafe safetyglass.

I believe there is a technique using a mirror on edge to look at a piece of glass and ascertain if it is laminated. I also believe all safety glass is marked as such.

Thanks to Craig, the OP for the nice article.
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Old 09-28-2012, 02:29 PM   #16
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Default Re: Unsafe safetyglass.

The technique I have heard of is holding a lit match near the window and looking for the double reflection due to the laminations.

The glass shops in my area do not mark my safety glass per my request. They never told me it's mandatory to do so.
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Old 09-28-2012, 10:46 PM   #17
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Default Re: Unsafe safetyglass.

Quote:
Originally Posted by 700rpm View Post
Isn't this what seat belts are for?
In an A, even with a seatbelt, your head WILL hit that windshield in a crash!

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Old 09-29-2012, 08:36 AM   #18
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Default Re: Unsafe safetyglass.

Where I am the cost of tempered glass is just shy of double the price of laminated.It has to be sent out to get tempered,and the closest place that did it went out of business.The glass guys cut it here,finish it,then box it up to go out for tempering.They don't have to box it like we would for UPS,but it does have to be protected enough to make a 40 mile ride in a truck with other glass piled in with it.Then it has to be picked up,unless you want to wait for the weekly delivery by them.I wouldn't do it in an A again,the strength is just not needed there.Because of the laminated glass in some of the modern stuff the rescue guys here are schooled in how to remove a piece of laminated in 12 seconds.My dad does a lot of remodeling in homes,he has gotten a lot of glass cut and tempered.That situation is different though,the safety factor is important there.You can't have a kid running full tilt into a glass cupboard door fitted with plate glass.I have a friend in the glass business that does mostly home and commercial work,but still does old cars and street rods because he likes them.He still does Model A windshields for $75.installed in the frame.I went to him for glass for my Tudor,he said the new tempering outfit was much better priced and it would only be a few dollars more.I would prefer tempered,so I said OK.He called a week later,told me they were ready but I didn't have to take them.The price was double.
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Old 09-29-2012, 10:02 AM   #19
Jerry Parr WI
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Default Re: Unsafe safetyglass.

Quote:
Originally Posted by tmiller6 View Post
Isn't it funny how in the Untouchables movie, that brace was missing when Frank Nitty fell off the roof and into the sedan parked outside the courthouse?
And the bows were prebroken and the fabric precut. Dummy wasn't heavy enough to brake that stuff from a few feet. My car was next to it.
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Old 09-29-2012, 10:24 AM   #20
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Default Re: Unsafe safetyglass.

Quote:
Originally Posted by Bruce Adams View Post
I believe there is a technique using a mirror on edge to look at a piece of glass and ascertain if it is laminated. I also believe all safety glass is marked as such.
I had read similarly using a business card, probably on fordbarn. Since a windshield is captive on the edges, I tried it on a then newly purchased SW sedan. It clearly showed the double image. Later, for whatever reason, I wanted to be sure. I retried the "card trick" on a known piece of plate glass. It showed the double image! I removed the windshield top piece and it was plate glass. Someone replaced the factory safety glass with plate probably to save money. Kinda scary when I thought back to drives made in the SW whereby a rock could have been thrown by a vehicle.

I went ahead and replaced all eight pieces of glass with new laminated. None is marked safety. They cut it out of a larger sheet.
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