12" Pyrex blanc exchange for 12" f/4 mirror

[Stefan Buda]

I need an old school full thickness 12" Pyrex blank and I'm willing to exchange for a 12" f/4 Pyrex, spherical mirror, with edge thickness of 40mm.

In other words, I need a thicker blank to make an optical flat.

[JA]

Hi Stefan,
Much smaller than what you want but here's some 6 inch Pyrex blanks.....
https://www.iceinspace.com.au/forum/showthread.php?t=196083

Best
JA

[Stefan Buda]

Thanks JA,

I have seen that add, but I need a 12" Pyrex that is about 2" thick.
A precision flat needs to have that kind of D/T ratio for rigidity.

My 12" mirror would be down to 35mm thickness by the time I flatten the front surface.