I have had to remove some ceramic wall tiles off my bathroom wall to repair the wall. They all came off fairly easily and in tact with most of the adhesive glue remaining on the back of the tiles. I now want to replace the existing tiles but cannot remove the tile adhesive. The adhesive is so hard it is impossible to chisel off (and possibly crack the tile)and I have even tried sanding the adhesive off but no good. Can anyone please suggest what I can use or do the remove the old adhesive.