Efflorescence
Efflorescence is the white, chalky, powdery deposit that forms on the surface of brick, concrete, stone, stucco, and block masonry when water dissolves mineral salts inside the material and carries them to the surface. As the water evaporates, the salts are left behind as a crystalline residue. It is cosmetic — not structural — but it is frustratingly persistent because every rain cycle can push more salts to the surface.
In depth
Fresh efflorescence on concrete or new masonry is often called "primary efflorescence" and usually fades within a year as the initial free salts exhaust. Recurring white deposits on established walls ("secondary efflorescence") indicate an ongoing moisture intrusion — failed flashing, missing weep holes, soil grading, or interior humidity — and cleaning alone will not solve it. Removing efflorescence requires a specialty masonry acid (diluted phosphoric or a proprietary blend), a thorough pre-soak, and careful rinsing. Pressure washing alone will redistribute the salts; the chemistry is what dissolves them.
How this shows up on our jobs
Efflorescence shows up on basement walk-outs, retaining walls, and brick chimneys across Madison. We diagnose whether it's cosmetic or a water-intrusion symptom before scheduling treatment.
Services where this matters
Related terms
Acid Wash
An acid wash in exterior cleaning is the application of a dilute acidic solution — most commonly muriatic (hydrochloric), phosphoric, oxalic, or a proprietary masonry blend — to dissolve mineral-based staining that bleach and surfactants cannot touch. Typical targets include efflorescence on brick, heavy rust from fertilizer or irrigation, mortar haze on new brickwork, mineral deposits on glass, and battery acid on concrete. Acid wash is not a general cleaning method — it is a targeted chemistry tool for specific stains on specific substrates.
Chelating Agent
A chelating agent is a chemical that grabs onto metal ions — calcium, iron, copper, magnesium — and holds them in solution so they can be rinsed away instead of bonding to a surface. The word comes from the Greek chele ("claw") because the molecule literally clamps onto the metal ion like a lobster claw. Common chelators include EDTA, oxalic acid, and citric acid.
Weep Hole
A weep hole is a small, deliberately-placed opening at the bottom of a brick-veneer wall, window frame, or storefront glazing that lets trapped water drain out. On brick homes, weeps are typically vertical gaps in the mortar every four to six bricks along the bottom course; on vinyl and aluminum windows, they are the small slots in the bottom of the exterior frame. Without weep holes, water that gets behind the brick veneer or inside the window frame has no escape path and causes efflorescence, mold, rot, and interior leaks.
Damp Proofing
Damp proofing is the application of a moisture-resistant coating or membrane to a masonry surface — most commonly foundation walls, brick veneer, and chimneys — to slow water absorption and reduce efflorescence, spalling, and interior moisture problems. It is less robust than true waterproofing (which forms a continuous, pressure-rated barrier) but more cost-effective and better-matched to surfaces that need to breathe.
Poultice
A poultice is a paste-like cleaning compound applied to a porous surface — natural stone, unsealed concrete, brick, limestone — to draw a stain out of the pores through capillary action. The paste is spread roughly a quarter-inch thick over the stain, covered with plastic, and left to dwell for 24-48 hours. As the poultice slowly dries, it pulls the dissolved stain out of the substrate into itself, where it can be scraped off and discarded.