I have an interior brick wall (fireplace) finished in a country style. The bricks themselves are not perfectly shaped. Some are intentially chipped and others are distressed. It also has dyed black mortar that I'd like to change. The mortar joint itself is recessed around a quarter inch, give or take, and flat for the most part. Can I mortar over this and make a flush joint? Would I have a problem with adherence or cracking? Thanks for any insight.