Question: Solar oven glass?

[Sensor Geek]

I'm looking for a glass or other substance suitable for a solar heater/oven expected to be on average about 400F with a max of 600F.

Some people apparently use standard 1/8th inch window glass with good results, but I'm a little concerned with safety and the possibility of the pane blowing up in someone's face as they work with this thing. That's not based on experience or knowledge of it happening to anyone, but I wonder about it. Is that a realistic possibility?

Whatever I use, it should be as transparent to visible & IR as possible, and naturally, cheap as dirt. This particular project will require a 24"x24" piece.

And finally, I have a trash can of broken window glass from trying to cut the stuff with only limited success (for other projects, not the oven). Any hints on cutting down large window panes into smaller parts?

Thanks!

[adafruit_support_mike]

Window glass probably won't be your best choice. You want tempered borosilicate glass (aka: Pyrex).

Windows are generally made from plain glass (called 'soda glass' because of the chemicals used making it), which tends to expand and contract a lot when the temperature changes. When one part heats or cools faster than another, you get the same effect as dropping an ice cube in hot water.

Borosilicate glass adds some boron to the mix, which reduces the thermal expansion. The hot glass is roughly the same size as the cold glass, so fast/uneven temperature changes won't rip it apart.

Tempered glass is heated, then cooled quickly. The surface shrinks faster than the inside, and you get a lot of stress trapped in the glass. That's actually a good thing when done properly. The internal stress pushes back against any force applied from the outside, and keeps the glass from breaking when you smack it.

Your best bet would be to look in the yellow pages for a fireplace and wood stove supply company in your area. They'll have panels of glass specifically made for high temperatures.