Oil-Based Stains (grease, tar, cooking oil, cosmetics) —Will darken the stone and normally must be chemically dissolved so the stain’s source can be rinsed away. Clean gently with a soft liquid cleanser, household detergent, ammonia, mineral spirits, or acetone.
Organic Stains (coffee, tea, fruit, tobacco, paper, food, urine, leaves, bark, bird droppings)—May cause a pinkish-brown stain and may disappear after the source of the stain has been removed. Outdoors, with the sources removed, normal sun and rain action will generally bleach out the stains. Indoors, clean with 12% hydrogen peroxide and a few drops of ammonia.
Inorganic Metal Stains (iron, rust, copper, bronze) — Iron or rust stains are orange to brown in color and leave the shape of the staining object, such as nails, bolts, screws, cans, flowerpots, or metal furniture. Copper and bronze stains appear as green or muddy brown and result from the action of moisture on nearby or embedded bronze, copper, or brass items. Metal stains must be removed with a poultice (see page 12). Deep-seated, rusty stains are extremely difficult to remove and the stone may be permanently stained.
Fire and Smoke Damage—Older stones and smoke- or fire-stained fireplaces may require a thorough cleaning to restore their original appearance. Commercially available smoke removal products may save time and effort.
Etch Marks (calcareous stones)—Caused by acids (typically from milk, fruit juices, alcohol, etc.) left on the surface of the stone, some will etch the finish but not leave a stain; others will both etch and stain. Once the stain has been removed, wet the surface with clear water and sprinkle with marble polishing powder. Rub the powder into the stone with a damp cloth or by using a buffing pad with a low-speed power drill or polisher. Continue buffing until the etch mark disappears and the marble surface shines. Honing may be required for deep etching. This process may require the services of a stone maintenance professional.
Biological Stains (algae, mildew, lichens, moss, fungi)—Clean with a dilute (1/2 cup in a gallon of water) ammonia, bleach, or hydrogen peroxide. WARNING: DO NOT MIX BLEACH AND AMMONIA! THIS COMBINATION CREATES A TOXIC GAS!
Ink Stains (magic marker, pen, ink) —Clean lightcolored stones with bleach or hydrogen peroxide. Use lacquer thinner or acetone for dark-colored stones.
Paint Stains—Small amounts can be removed with lacquer thinner or scraped off carefully with a razor blade. Heavy paint coverage should be removed with a commercial liquid paint stripper. DO NOT USE ACIDS OR FLAME TOOLS TO STRIP PAINT FROM STONE.
Water Spots and Rings (surface accumulation of hard water) —Buff with dry 0000 steel wool.
Efflorescence—A white powder that may appear on the surface of the stone, it is caused by water carrying mineral salts from below the surface of the stone to the surface and evaporating. When the water evaporates, it leaves the powdery salt residue. If the installation is new, dust mop or vacuum the powder. Repeat as necessary as the stone dries out. Do not use water to remove the powder (adding water will only add to the problem). If the problem persists, contact the stone contractor to identify and remove the cause of the moisture.