- This is probably “efflorescence,” also known as “alkali.” Efflorescence or alkali consists of salts leached from your soil when exposed to excessive, saturating moisture. It appears as a whitish powdery “bloom” on the surface of the wall. A wash down with white vinegar or another approved dilute acid solution, followed by a thorough flush with clear water will usually remove efflorescence. Taking care to direct sprinklers, irrigation systems, or other sources of water away from stucco walls will help prevent it.
- REMEMBER: always keep acids and other chemicals away from children, and ALWAYS use the proper safety equipment – including eye protection – when working with any hazardous substance!