What is the white powder or crust found on masonry walls caused by salt drawn to the surface by moisture?

• A. Bleeding
• B. Hydration
• C. Efflorescence
• D. Seepage

Answer: (C)

Salt-containing moisture moving through masonry brings dissolved salts to the surface. As the water travels and then evaporates, those salts crystallize on the surface, leaving a white, powdery crust known as efflorescence. It’s a sign of moisture moving through brick, concrete, or stone, not a chemical change in the cement itself. It’s different from hydration (the curing reaction of cement) and from seepage (actual water intrusion causing damp patches). To reduce it, limit moisture entering the wall, improve drainage and ventilation, and clean the crust as needed once moisture is controlled.