Oil-based (grease, tar, cooking oil, milk, cosmetics) An oil-based stain will darken the stone and normally must be chemically dissolved so the source of the stain can be flushed away. Clean gently with a soft, liquid cleanser with bleach OR household detergent OR ammonia OR acetone OR mineral spirits.
Organic (coffee, tea, fruit, tobacco, paper, food, urine, leaves) May cause a pinkish-brown stain and may disappear after the source is removed. Clean with 12% hydrogen peroxide (hair bleaching strength) and a few drops of ammonia.
Metal (iron rust, copper, bronze) Iron or rust stains are orange to brown in color and follow the shape of the staining object. Copper and bronze stains appear as green or muddy-brown and result from the action of moisture on nearby embedded bronze, copper, or brass items. Metal stains must be removed with a poultice. (See section of Making & Using a Poultice). Deep seated, rusty stains are extremely difficult to remove and the stone may be permanently stained.
Biological (algae, mildew, lichens, moss, fungi) Clean with dilute (1/2 cup in a gallon of water) ammonia OR bleach OR hydrogen peroxide. DO NOT MIX BLEACH AND AMMONIA! THIS COMBINATION PRODUCES A TOXIC AND LETHAL GAS!
Ink (magic marker, pen, ink) Clean with bleach OR hydrogen peroxide (light colored stone only!) OR lacquer thinner or acetone (dark stones only!)
Paint. Small amounts can be removed with lacquer thinner or scraped off carefully with a razor blade. Heavy paint coverage should be removed only with commercial “heavy liquid” paint stripper available from hardware stores and paint centers. These strippers normally contain caustic soda or lye. Do not use acids or flame tools to strip paint.
Paint strippers can etch the stone surface. Follow the manufacturer’s directions taking care to flush the area thoroughly with clean water. Protect yourself with rubber gloves and eye protection. Work only in well ventilated areas. Normally, latex or acrylic paint will not cause staining. Oil based paints, linseed oil, putty, caulks and sealants may cause oily stains.
Scratches and Nicks. Surface scratches may be buffed with dry 0000 steel wool. Deeper scratches and nicks should be repaired and re-polished by a professional granite fabricator.