Q: There is a white powder-like substance on the brick of our new backyard patio. How can I remove this?
A: That white substance is called efflorescence, often found on the surface of masonry, resulting from water-soluble salt deposits. Generally, efflorescence can easily be removed by natural weathering or by scrubbing with a brush and water. Proprietary cleaners formulated specifically for use on brickwork are effective in removing stubborn efflorescence. Make sure the cleaner is intended for use on brick and be sure to follow the directions on the label. Improper acid-cleaning procedures (insufficient prewetting, rinsing and strong acid concentrations) may cause additional staining or damage to the brickwork. All cleaning procedures should first be tried at different concentrations in an inconspicuous area to judge their effect and check for any potential harm to the brickwork. After cleaning, inspect the mortar joints. Repointing or grouting of the joints may be necessary. (Information provided by the Brick Industry Association)