Because of the settling of subfloors, or due to uneven installation of subfloors, floors may go uneven. This is called as lippage. Over time, there will be multiple scratches on the floor. A new marble to may have uneven surfaces. Grinding or scrubbing removes all roughness and ledges either it is Italian, Mosaic etc. It provides a flat shape to it. During this step, the stain and deepest scratches too get removed from the floor. For this process, grit size 30, as well as 50 diamonds, are suitable and effective.