I may be asking a dumb question, but anyway, why are some of my bricks pinkish and some white? And is the gaps between them supposed to be tight or slightly spaced? Across the back of my stove I have some large gaps in the corners where you can see the metal easily. Also, is it best to leave the ash between the bricks on the floor of the firebox or lift out the bricks and clean the floor of all ash? I have read that the ash insulates the firebox metal, is this true? Because the corners of my firebox are all exposed. Will the heat damage anything bare metal over time??