What is the correct way to mortar firebrick into a cast iron stove (A Waterford Stanley Ashing) The old bricks were set in a thin layer of what I assume is refractory cement? I had to remove them to replace a cracked inner back plate. Can refractory be mixed thin and used as mortar, instead of the thick consistancy that the directions request you to make it (Rutland). Or do you use something else to mortar in the brick and fill in voids in between them?