RadonSeal Efflorescence Cleaner (5-gal) &ndash; The Safe & Easy Alternative to Acid Cleaning | Removes Efflorescence From Concrete, Brick, Masonry Quickly & Safely Removes Efflorescence, Mineral Stains, and Lime Deposits. USER-FRIENDLY  Water-based, Non-Flammable, Biodegradable. SIMPLE APPLICATION Spray-On Application using a Hand-Pump "Garden/Bug" Sprayer. CONCRETE & MASONRY SAFE  Will Not Damage or "burn" Concrete or Masonry. BEATS USING ACIDS  Safe for Indoor or Outdoor Use.