Cleaning a granite sink can be an annoying chore, but if you use the wrong cleaning products, it can also cause permanent damage. Granite, like other natural stone surfaces, requires some tender loving care, and not just any cleaning solution is going to work.
For starters, you'll want to avoid all acids, even the weak ones. Vinegar is often touted as a great natural all-purpose cleaner, and that is usually true, but in this case, you'll want to keep the vinegar far away. Acetic acid (vinegar's acid ingredient) can actually dissolve natural stone surfaces. Other acetic products, like lemon juice and phosphoric acid cleaners, should also be avoided. Even mild household detergents can sometimes contain phosphoric acid, so you must be extra careful.
For best results, head down to your local home supply stores and pick up a pH neutral cleaner. These products are safe to use on granite surfaces and will not cause etching. Just dilute the cleaner with water if recommended by the manufacturer, and then pour the cleaner onto a soft, non-abrasive cloth, dampening the cloth. Scrub the entire granite sink thoroughly and rinse with water. Use towels to dry the sink by hand, since granite surfaces may develop water spots and mineral deposits.
In some cases, you may only need warm water to clean your granite sink. This can not only save you money; it can also ensure that you limit your granite's exposure to chemicals. For a quick polishing effort, try dampening a soft cloth with water and wiping down the entire interior of your sink.
In some cases, you may have seemingly impossible stains that require something even stronger than a pH neutral cleaner. For these rare emergencies, you may use a small amount of diluted bleach without hurting the granite. Handle the bleach carefully and dilute with AT LEAST four parts water. Apply the mixture to your non-abrasive cloth, scrub and rinse. You should not do this routinely, but in moderation it should not cause any damage to your granite sink.
You can also apply these precautions and tips to other natural stone surfaces, like marble, onyx and limestone. If you had your granite sink professionally installed, check your paperwork to observe any specific manufacturer's instructions for cleaning.