double paned glass in a 40
 

I'm disassembling a 40 sedan and all of the glass (windshield and side windows) are double paned. Not safety glass but two panes of glass....kind of like a storm window. Is this normal? All needs replaced but I thought it would be safety glass. Any thoughts?

Re: double paned glass in a 40
 

There are two types of safety glass. Today we use tempered glass everywhere in a car but the windshield. This glass is made by heat treating the class after it is cut. The glass is brought almost to a molten temperature. It is then hit with a blast of cold air to solidify the surface. As the interior cools it contracts. This sets up stress within the pane of glass. This stress causes the glass to break into thousands of harmless pieces when it is broken. In case of an auto accident the glass in the side windows can be broken with a sharp rap to reach passengers trapped inside. It is also probably cheaper to manufacture than the laminated. This glass in the windshield is laminated. There are two pieces of glass sandwiched around a plastic (acetate) core that keeps the glass from breaking into dangerous pieces. The tempered glass is not used in the windshield because you wouldn't want a windshield to shatter into a thousand pieces if hit by a rock on the freeway.The glass in the '40 was the same type that is used in windshields today.

Charlie Stephens

Re: double paned glass in a 40
 

The old safety glass was made with a clear Acetate sheet sandwiched between two layers of glass. With time the Acetate yellows around the edges. This was a big improvement over the Plate Glass used in the early 30's.

Re: double paned glass in a 40
 

Bart-you're going to have to take some pictures as everyone's response above reverences the commonly known safety glass construction.. If yours is truly like a "storm window"--it'd be interesting to see..

Re: double paned glass in a 40
 

Not much of it is left. All of the glass has come out in pieces. and I was unable to tell if the two panes were sealed at the edges but there appeared to be a 16th of an inch or so gap between the panes. I''' try to get some pics.

Re: double paned glass in a 40
 

It probably just separated by time and temperatures.

Re: double paned glass in a 40
 

I just removed the rear window out of my 1939 ford coupe and it came out in 2 layers with nothing in between, but I am sure the layer of plastic was completely deteriated.