Virtually every masonry contractor has run into the problem: efflorescence, the unpredictable white (or sometimes green) salt deposits that seem to attack masonry like a disease. What causes it? How do you prevent it? How do you remove it? THE CAUSES Efflorescence results when soluble salts in the masonry units or mortar leach to the surface. For efflorescence to occur, three conditions must exist simultaneously: soluble salts must be present within the masonry assembly; water must come in contact with the salts to form a solution; and the salt solution must migrate to a surface where the water can evaporate. PREVENTING EFFLORESCENCE Regardless of the impurity of the materials used, efflorescence is not likely to occur if proper precautions and high-quality workmanship are employed. To prevent efflorescence, follow these steps: use masonry units of low absorption; use mortars of high lime-cement ratio; cover the top course of unfinished walls; install proper flashing and weeps; and construct full, tight, weatherproof mortar joints. REMOVING EFFLORESCENCE You can remove most efflorescence by dry brushing then flushing with clean water. Heavy accumulations or stubborn deposits can be removed with a solution of 1 part muriatic acid to 12 parts water. Before applying the acid solution, always first saturate the wall with water so the acid doesn't penetrate deep into the wall and damage it.