For quick touch-ups, less is definitely more. Use a soft cloth microfiber cloth and warm, distilled water to clean marble countertops – especially after contact with food – and then use another
cloth to dry the surface. Marble is very prone to water spots, so it is a good idea to never let it air dry.
Prepare the surface of the marble by removing all dirt, grime, grease, waxes and stains with a commercial stone cleaner. You want to remove all these contaminants from your marble first so that you don’t force them deeper into the surface when polishing the marble.
You’re going to need more than warm water this time. That’s not to say you should go overboard; it is still important to remember that marble is delicate. A ph-neutral dishsoap is probably best when you do your deeper marble cleaning, but you may also use acetone (for dark marble only, to be safe), hydrogen peroxide (for light marble), or clear ammonia mixed with water. You can purchase a non-abrasive marble cleaner, of course, but shop cautiously. If you’re nervous about damage to the stone, visit a store that sells marble and they’ll be able to help you out. Whichever product you choose, be sure to rinse thoroughly so there’s no residue left, always dry completely, and make sure you don’t slip on your slick marble floor!
Just like acidic cleaners, acidic “stuff” in general is bad for your marble. This includes wine, orange juice, tomatoes and even soft drinks, so get any spills up right away by blotting them – wiping or rubbing can make the problem worse. If you’re left with a stain anyway, use a commercial marble stain remover (remember to choose wisely) or make your own. Try making a poultice (a “soft, moist mass” – not just a medical term) out of a fine powder like whiting or baking soda, going for a peanut butter-like consistency. For oil-based stains (cosmetics, grease), use the powder with some water or rubbing alcohol. For water-based ones (coffee, tea), mix the powder with either hydrogen peroxide or acetone. When you have your poultice, wet the stain and apply the mixture. Tape plastic wrap over it and let dry (usually at least 24 hours); the drying process should lift the stain out.
The safest and easiest way to polish marble is with a chamois (shammy) on a damp surface; the chamois will polish at the same time as it dries. If you want more shine, try a commercial polish and then dry with the chamois. You can also use baking soda and a stick of chalk to polish marble. First wipe your marble with a baking soda mixture (3 Tbsp. soda to 1 qt. water) and let it air-dry (this time it’s okay) for a few hours before rinsing it. Next, moisten a fresh cloth and dip it in crushed chalk, wipe your marble, then rinse and dry thoroughly.
Because marble is quite porous, it is wise to use a sealer to protect against staining and interior damage. A sealer isn’t foolproof, but it resists moisture for a lot longer than a surface that is not sealed; this matters when it comes to spills or mud on the floor – it buys you time, at least. Before applying a marble sealer, try to find out if and when sealer was applied and what brand was used. Some sealers need to be re-applied every year or two, others every fifteen to twenty years. If you do apply a marble sealer, be sure to use one that is nontoxic and – if you’re using it on countertops – safe for food preparation.