We're planning on installing a direct vent gas fireplace in our 100+ year old house's living room and want to install a vintage fireplace mantle and beautiful old 1"x2" ceramic tiles that we found (they may be marble - we are not sure). The tiles have the old mortar and backing still attached. To make a clean installation, we want to take off the tiles from the old backing, remove the old mortar, clean the tiles and reinstall them. What is the best method of removing the mortar and cleaning the tiles?