Can You Use Sandpaper to Get Etchings Off a Brick Wall?

Efflorescence

• Efflorescent salt is a fine, powdery deposit that appears on walls made of brick or other masonry units when moisture carries dissolved salts to the surface of the bricks and evaporates, leaving the salt. Although sandblasting has traditionally been used to remove efflorescent salts, it can damage the wall and increase the absorptive nature of the bricks and mortar. Instead, use a dry brush with stiff bristles to brush the salts off the surface. A brush may be used in conjunction with rinsing, but this may simply force the salts to migrate downward. Alternatively, if the wall was constructed recently and the efflorescence is somewhat uniform or not extensive, natural weathering and precipitation may effectively remove the salts.

Removing Lime

• Lime, or calcium carbonate, generally appears on a brick wall or other masonry surface as a crusty, thick, light gray deposit. Unlike the salts that appear on the brick faces as a result of efflorescence, lime deposits do not have a salty taste. Remove lime stains by wetting the surface of the wall, brushing the stains with a diluted acid solution and rinsing the wall clean after the acid is utilized. A mason's or rubbing stone may also prove helpful when grinding off the deposit.

Other Types of Staining

• A number of other types of stains may appear on a brick wall. Remove biological stains using some combination of brushing and water sprays and, if necessary, a muriatic acid-based cleaning solution. Green or cream-colored stains on a newly-constructed brick wall could be caused by Vanadium salts. Address the salts by scrubbing them with an acid solution, rinsing thoroughly with water and following that with a potassium hydroxide wash to leave the wall alkaline. Black or brown iron or manganese stains should be treated with a 5 percent hydrochloric acid solution, or an oxalic acid solution can be painted over the stain.

Preventing Efflorescence

• Efflorescence can only occur if there are water-soluble salts present in the wall, if there is enough moisture in the wall to dissolve the salts into a solution and if there is a pathway for the moisture and dissolved salts to reach the surface of the wall where the moisture can evaporate and deposit the salts. Reducing any or all of these conditions will help to limit efflorescence. Limit the amount of water that comes into contact with the wall. On a structure, use overhanging eaves and flashing and avoid directing a sprinkler or other landscaping water toward the wall. Only use as much water as needed when mortaring during construction. Brick walls that are retaining earth may be more vulnerable to efflorescence. The earth-retaining side of the wall can be covered with a waterproof membrane as long as drainage is adequately accounted for.