I have sucessfully used (many times) patio tiles of cement that you can purchase at the local garden shop for a couple of bucks. I used this as a substrate, sealed it thuroughly, and glued ceramic tiles to this. They are great and easy to make. For polishing I used the same, with a hard plaster layer shaped by the mirror sealed up well with Rust-O-Leum paint (don't use varnish as outgassing will soften pitch!!). The pitch was poured on this. I used machines of my own construction so weight was not a problem.-Rik