Just so anyone who isn't clear about the terms can understand:
Pyroceramic is the proper name for a fused glass type that can withstand high temperatures.
But to understand that, we need to understand what is going on.
What a ceramic is is a non-metallic material ( usually crystalline, but not always...as in glass) that has been fused by heat to make it stronger and more heat resistant. Pottery is the simplest form of ceramic. Clay and some simple compounds can be fused at high heat into a strong and much harder material. Other materials, like glass, can be modified and/or treated to make them have ceramic properties. Many ceramics appear to be metals, but are not. The rare earth magnets, and many hard tooling faces are actually ceramic. They even make ceramic knife blades.
Plain glass or just tempered glass will not work successfully as a platen. I am sure someone does it, but the failure rate has to be high.
Ceramic bath tiles are only clay tiles with a ceramic coating, and not what you want either.
Pyroceramic, AKA ceramic glass or pyroceramic glass, is what the suppliers sell. They have it made to size and sell pieces that will fit most any tool. You can have a piece custom cut for an odd grinder.
You can round the edges on the grinder with a good sharp belt, but go slow, as no glass like this type of treatment. As far as roughing up the back, that may actually be counter-intuitive. Glass ruptures along any line of weakness. Sanding and roughing up the back will create millions of these places. A good cleaning and the proper adhesive should bond the glass surface just fine.
