MAINTENANCE : The Dirt on Care of Masonry

Although concrete and other masonry surfaces generally require little maintenance, they do get stained and soiled.

The safest, least abrasive way to clean older structures is by scrubbing with water and a stiff-bristled fiber brush. If water isn’t enough, add a mild household detergent. Don’t use a steel brush; it may leave scratch marks and cause rust stains.

If you decide to use specialized concrete or masonry cleaning products, remember that they can be corrosive and highly toxic so it’s important to handle them with care. Always test a cleaner on an inconspicuous part of the surface to be cleaned. Saturate the surface with water before and after applying a chemical cleaner.

A heavy accumulation of dirt may require steam cleaning, high-pressure water blasting or sandblasting. These are best left to qualified cleaning contractors.

You can scrub paint specks and mortar smudges from masonry surfaces with a broken piece of matching masonry--brick, stone, concrete or concrete block. For brick, use a broken piece that’s the same color as the brick you are cleaning. Use only the broken surface of the brick. The face of the brick is harder than the core and can cause scratches.

Lift out oil and grease stains from masonry with dry powdered cement or cat litter. Spread a layer over the stain, allow it to soak up the oil overnight before sweeping the area clean. Repeat if necessary. Then scrub the area with scouring powder or masonry detergent. Rinse well with water.

Scrape off asphalt, tar or pitch from masonry. (Applying dry ice to molten tar makes it easier to remove.) Scrub the stain with scouring powder and water, then rinse. If the stain has penetrated deeply, apply talc or whiting mixed with kerosene. Let stand until it dries, then brush off with a stiff-bristled brush. Scrub with scouring power, then rinse well.

Copper or bronze stains on masonry can be treated with a mixture of one part ammonium chloride (sal ammoniac), four parts talc or whiting and enough household ammonia to make a smooth paste. Apply to the stain and let dry, then brush off and repeat if necessary. Scrub and rinse with water.

For graffiti on masonry, apply a commercial spray-paint remover, following label directions.

To remove smoke stains, scrub with scouring powder and rinse with water. Cover persistent stains with talc or whiting mixed with laundry bleach.

Soak up wet paint with soft cloth or paper towels; don’t spread the paint as you blot. Scrub the stain with scouring powder and water. Wait three days and then treat as you would dry paint stains.

To remove dried paint, scrape off as much as possible. Then apply paint remover, following label directions. Scrub off any residue with scouring powder and water. If the color has penetrated the surface, try removing it with a weak solution of nine parts water to one part hydrochloric (muriatic) acid (available in hardware stores).

Don’t use acid cleaners on stones or on black, gray, brown, tan or light-colored brick.

Iron rust on masonry can be removed by brushing on a solution of one pound oxalic acid crystals in one gallon of water. Let stand three hours, then scrub and rinse with water.

To remove chewing gum from concrete or block, use an ice cube to harden the gum, then scrape it off. Apply a mixture of denatured alcohol and talc or whiting. When dry, brush with a stiff-bristled brush. Scrub with scouring powder and rinse well.

For mildew on concrete or block use a soft brush to apply a solution of one-ounce laundry detergent, three ounces trisodium phosphate (TSP), one quart chlorine bleach and three quarts of water. Rinse with water.

To kill moss on brick, apply weed killer according to label directions. Remove residual stains by using the treatment described above for mildew on concrete surfaces.

On marble, wipe off dirt with a damp sponge and buff dry. For stubborn dirt, apply borax with a damp cloth, rinse with warm water and buff dry. To take off oil or grease stains, apply talc or whiting mixed with acetone (nail polish remover). Let it stand overnight, then brush off and buff. For food stains, mix talc or whiting with hydrogen peroxide and a few drops of household ammonia.

Wash granite with a mild laundry detergent, rinse with water and wipe dry. Polish with a piece of chamois. Scrub limestone and sandstone with a stiff-bristled brush and water; don’t use detergent on these stones. Wash slate with a mild laundry detergent and rinse. Then place slate on a dampened felt pad and polish with pumice powder. Wash synthetic stone with a mild laundry detergent. If that fails, scrub with fine pumice powder and rinse with plenty of water.