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Mirror blank.....what is this material?

Started by gceee, 07/29/2013 04:50PM
Posted 07/29/2013 04:50PM Opening Post

I recently picked up a blank. Owner said it was his dads and it was way old. It doesn't look like Pyrex. It has a light brown/yellowish tint to it. Can anyone tell me what type of glass this is? Thanks,Gerry

Attached Image:

gceee's attachment for post 57663
Posted 07/29/2013 05:09PM #1
Looks like might be Pyrex .
Pete
Posted 07/29/2013 06:38PM | Edited 07/29/2013 07:03PM #2
Gerry, I don't think you can rule out Zerodur, which has been around since the late 60s. I've never seen Pyrex with that tint. In any case it should make a nice mirror.

George

Attached Image:

ks1u's attachment for post 147403
Posted 07/30/2013 04:56AM #3
I have some older Pyrex blanks, and the molding looks identical to your photo, with a raised rim around the back. One 10" blank has a yellowish tint similar to yours.

Pyrex is less dense than plate (2.23 g/cm^3 versus ~2.5 g/cm^3), so you could weigh it and measure its volume and calculate the density for a reality check.

Clear skies, Alan
Posted 07/30/2013 06:09AM #4
Gerry Stowe said:


I recently picked up a blank. Owner said it was his dads and it was way old. It doesn't look like Pyrex. It has a light brown/yellowish tint to it. Can anyone tell me what type of glass this is? Thanks,Gerry

It looks like Zerodur or Astrositall. As suggested earlier, you could weigh the blank and divide by its volume to get the density:

Pyrex 2.23 g/cc
Astrositall 2.46 g/cc
Zerodur 2.52 g /cc

http://www.fpi-protostar.com/bgreer/properties.htm

Jim McSheehy