Please help me identify safety glass

[stvaughn]

Based on comments from a previous post that I needed to replace my original plate glass windows with safety glass I have removed all six side windows and the rear window. I am 99.9% sure that these windows are original to the car based on the condition of the window channel and the window setting channel.   All the windows are solid plate glass. At some point in the not to distant past I believe that the windshield rubber gasket was replaced based on the soft pliable condition of the gasket. The windshield has an old appearance to it and I’m trying to decide if possibly it has been changed to safety glass when the gasket was changed before I remove it from the car. There are no markings on the windshield. 

 

Posts on the prior thread indicated that I could tell the difference by the reflection of an object in the window. I used a large washer to compare the reflections of the plate glass and the old windshield to the tempered glass and laminated windshield of my truck and my 73 year old eyes can’t tell the difference. I get multiple reflections with all the windows. Please tell me what exactly I should be seeing with the different windows. 

 

Thanks, Steve 

Edited December 24, 2018 by stvaughn
Additional information (see edit history)

[jpage]

Look at the edges of the glass for a very fine line in the center. This would indicate the plastic sheet between the glass if it is safety glass. Also look for any fogging or bubbling around the edges under the glass as this show delamination of the 2 pieces. In any case, you'll want to replace it with safety glass for your own personal safety. No one will be able to tell the difference . In fact, I'm not sure that glass companies can sell anything other than safety glass for automotive use unless it's OEM modern glass. Aside from that, you'll know for sure if you break it!

Edited December 24, 2018 by jpage (see edit history)

[stvaughn]

I edited my post to clarify that I have not removed the windshield hoping that it already is safety glass. 

[edinmass]

By 1932 safety glass was in very wide use.....did anyone not use it? Reo was not the low end market, so I would have expected it to have used safety glass by then. 

[60FlatTop]

36 minutes ago, jpage said:

In fact, I'm not sure that glass companies can sell anything other than safety glass for automotive use unless it's OEM modern glass.

 

Hollywood can get it. I think they buy it from their explosive suppliers.

 

Real Continental glass don't do that.

 

[stvaughn]

2 hours ago, edinmass said:

By 1932 safety glass was in very wide use.....did anyone not use it? Reo was not the low end market, so I would have expected it to have used safety glass by then. 

Ed,

 

This is what I can tell about the glass I took out. One of my door windows had a long running crack that went all the way through the glass, none of the glass I took out is laminated and when I took the windows to the glass shop they commented about it being plate glass. Also the Model S was REO’s lower priced model. 

 

Steve

[MikeC5]

I would guess there is some difference in refractive properties but I don't know how you would test that.  I would also guess that when tapped, plate glass and safety glass of same thickness would sound different (I expect the plastic layer to dampen the vibration) but an experienced ear would be needed.

[jpage]

Ford first started using safety glass in 1928 in windshields only and later started to use it as standard practice. Many other makes may have also used safety glass in the windshields while continuing to use plate glass in all other windows.

[Paul Dobbin]

When in doubt, buy Safety Plate for windshields and the same or Tempered glass for side & rear glass windows.

[wayne sheldon]

Fifty years ago, Jack Passey told me to use a shiny new quarter to check the reflection. It works. However, everybody's eyes are not the same. And not all glass is alike. Over the years, I have met many people in the hobby that use the quarter and find it works very well. Other people have trouble with it. 

To test unknown glass for laminated safety plate. Look at a bright reflection at about a 45 degree angle. Most people will see One reflection with plate glass. However, there are actually two reflections with plate glass. The first reflection will be on the first outer surface of the glass. The second, and lighter or lessor, reflection, will be on the inner surface of the other side of the glass. Many people do not see this second reflection in part due to the diminishing affect (diffusion) of the reflection from inside the glass.  This at least on most plate glass (the color and quality of glass does make a difference).

On laminated safety plate glass, there are actually two thinner pieces of plate glass laminated together creating a stronger glass that cannot shatter into knife-like pieces. Laminated safety plate glass will have a first reflection on the first outer surface of the glass (just like plain old plate glass). There will also be a second reflection on the laminated surface of the second sheet (plate) of glass which will be almost as bright as the first reflection. If one looks carefully, and has the "eyes" to see it, there will also be a third reflection again on the inner surface of the far side of the second plate.There will actually be a fourth reflection on the inner surface of the first sheet of glass, however, it will also be diminished slightly by the inner glass diffusion, and, because the laminated material is very thin, that minor reflection and the brighter reflection on the laminated surface of the second sheet will be so close together that most people will not be able to perceive it.

 

Over the years, I have told a few people that they should gather several old pieces of glass, both simple plate glass, and a few pieces of laminated safety plate glass. Using pieces that you can KNOW which they are, look at them in different lighting conditions to get a "feel" for how laminated looks as compared to simple plate. Remember, look at the reflections at an angle. The more angle, the more separation between the reflections (they WILL be very close together!).

A quarter works.  A shiny flat washer can work. A small light bulb, flashlight, Christmas tree string lamp are favored by other people. And a small candle flame also works very well (don't burn down the garage!). Remember, a small shiny object, or light, at an angle against the glass. Once you feel comfortable with seeing the reflections on known pieces of glass? Try it on that framed windshield you want to figure out. If it is safety plate? You will probably know in seconds.

 

And by the way. Although I think Reo probably used laminated glass in the windshield in 1932? In most states, there was no law requiring replacement glass to be safety glass until much later ('50s I think?). So it is very possible that plate glass may have been installed later as a replacement if one was ever needed.

[stvaughn]

Thank you Wayne for your excellent explanation. I will do as you suggested and practice on different known pieces of glass. I hadn’t considered the fact that my windshield could be a replacement and still be plate. The only way I ever going to be comfortable with the windshield is to pull it out and replace it. 

 

The glass shop I’m using is not an auto glass shop and they can’t etch a safety glass logo. I would like to find some way to etch the glass with a small logo on each piece. 

 

Steve