Acid wash will clean dingy brick

July 02, 2005|by GENE GARY / Copley News Service

Q: Some brick trim on our home has unsightly white film on it. I tried scrubbing the brick with household bleach and water without success. Do you know of any chemical that would remove this whitish film from brick?

A: The condition you describe is most likely efflorescence. It is caused by the presence of moisture working its way though the brick and bringing water-soluble salts to the surface that are originally present in masonry materials. These salts are deposited on the surface when the water evaporates.

Masonry cleaning and etching preparations are available at masonry supply stores, which will remove soil and various stains, including the white spots. Or, you can use a solution of muriatic (hydrochloric) acid. Mix 1 part acid to 9 parts water by volume. Use great care when working with acids. Wear old clothes, rubber gloves and eye protection. In making the mixture, pour the acid into the water a little at a time and very slowly to avoid any splashing. Never pour water into acid.


When using this solution on your brick, it is important to presoak the brick with plenty of water before acid washing. It is just as important to follow the treatment with a thorough rinsing of fresh water. A word of caution. Avoid acid cleaners on glazed or light-colored brick. Even when dealing with red brick or darker colors, it's best to test any cleaning solution on an inconspicuous area before proceeding.

Because the mineral composition of brick can vary from area to area, some cleaners can react with them in unexpected ways. For example, an acid used on bricks with high copper content could turn them green. Once your brick has been cleaned, prevent the return of efflorescence by sealing the surface with a water-resistant coating. Your masonry supply outlet or a well-stocked home center will have both clear sealers and those that come in colors that are particularly suited to masonry surfaces. The pigmented sealers can give you a richer, deeper red and emphasize the color of your natural brick.

Q: Six months ago I painted our basement floor. The paint coating looked great until it began to peel and flake recently. How can I remove the existing coating? Is repainting a feasible option or should I invest in another type of floor covering? Any suggestions would be helpful.

A. Paint peels from concrete floor for a variety of reasons, but the chief ones are: use of the wrong type of paint, improper preparation, or a moisture problem in the slab.

Test for a moisture problem by securely taping 2-foot-square pieces of polyethylene plastic on the bare concrete surface in two or three spots around the room (before taping you will have to scrape away old paint and allow the concrete to dry). Firmly seal all edges with duct tape. Leave the plastic in place for 72 hours, then take a peek. If the surface of the concrete underneath shows signs of dampness or darkened spots caused by moisture, you will know the slab has an internal moisture problem that will probably make a successful paint job difficult to achieve.

Moisture can sometimes be corrected by improving drainage around the slab - fixing rain gutters and re-grading to make sure rainwater runs away from the foundation. Application of masonry sealer before painting (and after etching, if required) will correct some moisture problems. If the slab passes the moisture test after treatment, the next step is to remove as much of the existing paint as possible.

Start by scraping and wire brushing away loose material. The remaining paint can be removed by a water-based paint remover, sanding with coarse sandpaper in a belt sander, or sandblasting. It won't harm the new finish if some bits of paint remain.

For smooth concrete, an etching solution will help make the concrete more porous and provide for better paint adhesion. Special concrete etching solutions are available through masonry supply outlets, paint suppliers and home centers. Examples are Standard Brands "Clean & Etch" and Bondex "Garage Floor Etching Compound."

Irregularities on the concrete surface should be filled with vinyl concrete patching compound. In addition, cracks should be opened with the pointed end of an old-fashioned bottle opener and brushed away with a wire brush. Clean the areas with a vacuum and fill them with vinyl concrete patch. Any large gaps should be filled with silicon-latex concrete caulk. Hairline cracks will not require repair. Allow patching to dry thoroughly.

Before painting, be sure that dirt, grease and oil are removed with a 10 percent solution of caustic soda, trisodium phosphate or detergents specially formulated for use on concrete. Be sure to rinse with clear water to remove any trace of cleaning agents.

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