I found an used glass sheet 1/2" thick at a used furniture store! Now I can cut glass circles to make mirror blanks out of it!

I printed out some paper and taped it together to make a big circle Looks like I can get two 13" blanks and two 12" blanks out of this glass, all 1/2" thick. Or maybe should J do four 12.5" circles for consistency?

The scoring tool cut a circle fine, but then the next step was supposed to be "press it from the rear side and the crack will deepen", and it just... Didn't. Maybe this glass is just too thick? I still have half my countertop left, I need a new way to cut 1/2" glass