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View Full Version : What is this odd flat glass?


Mike Firth
09-25-2007, 02:14 AM
I scrounged a popcorn popper cart from the side of the road because it looked interesting and I could use the pot and the wheels if nothing else worked.
It turned out the only thing wrong with any of the parts was that a critical gear for stirring the popcorn was missing - motor, light and pot worked. Since I had no desire to go into the popcorn business or store the thing, I stripped it down.
And thus we get to the three glass panels around the pot that hold the popped corn for serving (along with Plexiglas doors)
Tonight I need a rectangle of single strength glass to photograph through and support stuff in front of it. For various reasons, I want to take 1.5 inches off the side. I get out my trusty glass cutting tools, my big flat board that I use for cutting (then put away to avoid mixing glass bits and ??)
I use one of my diamond scoring tools and make a lovely scratch and set up to pop the scratch across a rod. Lean on it - nothing. Apply pliers. Not much. Get out my C-clamp tensioner - nice cracking sound.
And the line snakes across the glass in lovely S curves that if it were a road, I would be looking for a sports car to drive it. The last time I saw something like this it was when the hot blast of a fire hit frozen cold window glass in our house fire.
I tried a couple of more breaks and got some really interesting pieces.
I switched to a carbide wheel and got hardly a scratch. Moved over an inch and leaned on it while pulling and got something not worth talking about.

So what is the glass? Not marked as tempered and certainly didn't shatter. Heat resistant? Surface tempered by some process? I am working at night so won't have the polarized light of the sun to look at the glass until tomorrow.

Steve Beckwith
09-25-2007, 03:31 PM
Sounds to me like heat strengthened glass (as opposed to tempered glass). It would be heat treated to give it better resistance to the hot oil and popcorn. In commercial applications, heat strengthened glass would be used in an exterior glass facade on a building between floors (the glass would have a fired on colored finish to make it opaque, the finish would be installed on the interior side) to conceal the all of the mechanical systems would be exposed if the glass were clear. In the same application, float (plate) glass with a finish on the interior would crack when exposed to the sun. Tempered glass would explode into a zillion pieces if you managed to get a score mark on it and tried to break it, heat strengthened glass will break into wild curvy pieces and not follow a cutter mark.