Type of Stains & First Cleaning Actions
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 or rinsed away. Clean gently with a soft, liquid cleanser with bleach OR household detergent OR mineral spirits OR acetone. A poultice may also be used. See below under Making and Using a Poultice for a recipe.
Organic (coffee, tea, fruit, tobacco, paper, food, urine, leaves, bark, bird droppings)
An organic stain 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 (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 such as nails, bolts, screws, cans, flower pots, 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 section below for making and 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 diluted ammonia OR bleach OR hydrogen peroxide (1/2 cup per gallon of water). DO NOT MIX BLEACH AND AMMONIA! THIS COMBINATION CREATES A LETHAL AND TOXIC GAS!
Ink (magic marker, pen, ink)
Clean with bleach or hydrogen peroxide (light colored stone only!) or lacquer thinner or acetone (dark colored stone only!)
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 “heavy liquid” stripper available from hardware stores or paint centers. Do not use acids or flame tools to strip paint from stone. Paint strippers can etch the surface of the stone; re-polishing may be necessary. Follow the manufacturer’s directions for use of these products, taking care to flush the area thoroughly with clean water. Protect yourself with rubber gloves and eye protection, and work in a well ventilated area. Use only wood or plastic scrapers for removing the sludge and curdled paint. Normally, latex and acrylic paints will not cause staining. Oil-based paints, linseed oil, putty, caulks and sealants may cause oily stains.
Water Spots and Rings(surface accumulation of hard water)
Buff with dry 0000 steel wool.
Fire and Smoke Damage
Older stones and smoke or firestained fireplaces may require a thorough cleaning to restore their original appearance. Commercially available “smoke removers” may save time and effort.
Etch Marks are caused by acids left on the surface of the stone. Some materials will etch the finish but not leave a stain. Others will both etch the surface and leave a stain. Once the stain has been removed, wet the surface with clear water and sprinkle on marble polishing powder (available from a hardware or lapidary store). Rub the powder onto the stone with a damp cloth or by using a buffing pad with a low speed power drill. Continue buffing until the etch mark disappears and the marble surface shines.
Efflorescenceis 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 rising through the stone and evaporating. When the water evaporates, it leaves the powdery substance. If the installation is new, dust mop or vacuum the powder. You may have to do this several times as the stone dries out. Do not use water to remove the powder; it will only temporarily disappear.
Scratches and Nicks
Slight surface scratches may be buffed with dry 0000 steel wool. Or, refer to the above sections on etch marks and follow the polishing procedure. Deeper scratches and nicks in the stone can be re-surfaced and re-polished in our shop.