Outdoor brick walls can become stained with white water marks known as efflorescence. Exposure to water causes water-soluble salts and minerals within bricks and mortar to transfer to brick wall exteriors. When the moisture evaporates, those deposits are left on brick wall facings. Although efflorescence visually mars brick walls, the white powdery deposits are harmless. While inhibiting moisture from entering brick walls is the only method of completely stopping efflorescence, you can use basic techniques to remove efflorescence from brick walls.
Scrub the brick wall vigorously with a nylon brush. Keep the bristles dry to avoid introducing additional water into the brick wall. Remove as much powdery white efflorescence residue as possible by scrubbing.
Moisten a cloth with water and wipe the brick wall to eradicate the loosened dust.
Examine the brick wall for heavy efflorescence deposits too stubborn for basic scrubbing with the brush. If heavy powder persists, fill the spray bottle with undiluted white vinegar and mist heavy efflorescence deposits. Don’t saturate the marks, just moisten them.
Scrub the vinegar-moistened efflorescence residue, using the nylon brush. Fully remove the remaining powdery stains from the brick. No rinsing is necessary.