Granite can become marked from many different things, including from lemon juice and colored liquids. These can cause etching and deep stains that can be difficult, sometimes even impossible, to remove. Hard water stains on granite are actually the result of mineral deposits left on the stone when the water dries. Normally these can be eradicated by rubbing or buffing to get rid of the spot.
The first step in removing hard water stains on granite is to make sure that the water is actually the problem. Running a finger lightly over the surface of the stained area can help in this process. If the stained area feels rough and goes below the surface, the problem is most likely etching caused by a food or drink spill. Such defects may require the help of a professional.
The stained area may feel more like an accumulation of something on the surface of the granite. It may also feel as smooth as the rest of the surface. In this case it is likely a hard water stain and can almost always be removed. The exact treatment depends on the severity of the stain, but in general it can be gently rubbed with an abrasive until it disappears. Before attempting to remove hard water stains on granite, it is best to test the abrasive on a hidden area, to see how it will affect the look of the stone.
One of the easiest methods for getting rid of a stain is to use marble polishing powder. This gently abrasive powder is sprinkled over the damaged area, then sprayed with water until it is slightly damp. A clean cloth is used to rub the powder firmly into the surface of the granite. When the powder disappears, the stain will typically be gone as well. For severe hard water stains on granite, this may take more than one application.
Another way to remove hard water stains on granite is to buff the area with very fine steel wool, size 0000. The stain should be lightly rubbed in a circular direction until it is removed. This will usually get rid of marks that range from very faint to quite significant.
Once the discoloration has been removed, the area that was stained may have lost some of its shine. Polishing powder or spray can be used to make the area match the rest of the surface. Usually all that is required is for the surface to be sprayed and then rubbed with a soft cloth until the shine is restored.