I had a silver black riven slate floor laid last weekend which has also been grouted. I'm now trying to clean the tiles before I seal them (no comments about pre sealing please - doh!). I've bought an HG product (Limex I think) for cleaning them but where the tiles are really riven it's difficult to get them completely clean - so my question is can I use the solution neat with a wire brush or will that destroy the face of the tile?