Efflorescence is the name of the chemical process causing the unsightly, but harmless, residue you have noticed. We see this problem in cementicious products such as concrete foundations and stucco walls. Efflorescence occurs as a result of concrete's relatively high porosity and acute mineral salt content. Flooding from rain water and garden sprinklers dissolves the minerals and carries them through the porous hollows of your foundation to the exterior surface, where evaporation leaves the white powdery remains. The effect is heightened considerably when the water causing the occurrence contains its own high level of minerals.

A 10% solution of muriatic acid, a bristle brush, gloves, eye protection and a bit of elbow grease are all that are needed to whisk away your problem. Soak the area thoroughly with the acid solution, let stand for a minute or two, (don't let it dry out), scrub vigorously for another minute or so, and rinse with a garden hose.

Caution: Muriatic acid may damage plants. And if you are using the solution to clean brick, test a hidden area first- this formula has been known to dissolve some finishes. A similar precaution should accompany cleaning stucco- colors could be bleached out.