Granite counter tops and floors, beautiful though they are, require special care and attention if they are to retain their beauty. These polished stone surfaces are subject to damage by different types of cleaners and abrasives. Granite also may be subject to water spots caused by mineral deposits from hard water, and water rings from glasses left to sit unprotected on the stone for too long. In most cases, you can remove water spots and rings with some gentle handling.
Determine if the marks you want to remove are caused by water; if they are, they can be removed. Something spilt that caused the stone to be etched is harder to deal with. Etching can be caused by any sort of an acidic liquid, such as lemon or orange juice, and leaves a rough spot that can be felt. Water marks are caused by a build-up of dried minerals from the water on the surface of the granite.
Test the surface of the granite in a hidden area to make sure you can proceed with rubbing away the spot before trying to remove water rings and spots in any visible areas. If it appears you are damaging the surface of the stone, stop and call for professional help.
Gently rub the water marks with very-fine 0000 dry steel wool. Use a circular motion and a very light touch. This removes accumulated minerals without harming the granite surface. If you prefer, you may use a commercial compound made for removing water marks and build-up from granite. Again, test it on a hidden area before using it on a more visible surface. Dampen the area with water from a spray bottle and gently rub to remove stains.
Apply polishing powder per the manufacturer's instructions. Slightly spray the powder with water to dampen it. Gently rub the granite with a clean cloth until the area begins to shine. Use a fresh cloth to remove any excess water and powder to complete the process.
To prevent water marks, never set anything wet or that might accumulate condensation on a bare granite surface. Always use coasters or other surface protection. If water splashes on granite surfaces, wipe it dry immediately.
If you can feel roughness on the polished granite surface, you most likely are dealing with etching and not simple water marks. Etching may require different treatment than described here. If it is deep enough to be easily felt, consider hiring a professional to polish and recondition the surface.