How to Remove Stains From Brick: Mortar, Black, Water, and White Stains

Brick stain removal starts with identifying the stain type, because mortar, efflorescence, black staining, and water damage each require a different approach.

Fresh mortar, salt deposits, soot, and moisture stains each respond to different methods, and some common fixes make things worse. Here’s what each stain is and how to remove it without damaging the brick.

How to Remove Mortar Stains From Brick

Mortar splashes must fully harden before you touch them, and never use an acid strong enough to etch the brick. Wait at least seven days after masonry is finished — the Brick Industry Association’s minimum; some references suggest 28 days for heavy splashing.

Knock off big clumps with a wooden paddle or other nonmetallic tool; avoid metal scrapers, which can scar and discolor brick.

For what remains:

• Pre-wet the brick and masonry below until saturated, so cleaner doesn’t soak too deep.
• Apply a manufacturer-recommended cleaner from the top down with a stiff-bristle brush.
• Scrub the brick, not the mortar joints; don’t let solution dry on the surface.
• Rinse thoroughly with fresh water.

Never use unbuffered muriatic or hydrochloric acid, and never hydrofluoric acid. Manufacturer instructions take priority. If you’d rather skip the guesswork, a roundup of manufacturer-approved brick cleaning products covers what to look for.

White Stains: Removing Efflorescence

White stains are usually efflorescence — salt pushed to the surface as moisture moves through masonry. Start dry, because washing can pull more salt out and make the haze return.

Brush with a stiff fiber brush first. Water is fine where needed, but heavy soaking can trigger a fresh bloom. Per the Brick Industry Association, persistent or hard-to-identify deposits should be professionally tested before chemical treatment.

The stain is a symptom. If you don’t fix moisture entering through defective flashing, weeps, sealants, or bad drainage, it will return. Dry-brushing plus correcting the water source is the fix — a chemical cleaner alone is not.

Black Stains and Water Stains

Black stains require identification first, because organic growth, soot, pollution, and metallic residue look similar but need different products. Don’t reach for a stronger acid: improper hydrochloric acid use can dissolve manganese compounds and leave a brown or tan stain harder to remove than the original. That manganese discoloration generally needs a proprietary masonry cleaner for metallic stains, applied after the source residue is gone. Mild cases sometimes fade with weather, but don’t count on it.

Water stains point to moisture penetration, so inspect brick units, mortar, weeps, flashing, and sealant joints before cleaning. Let masonry dry completely first — one manufacturer specifies at least 24 hours after cleaning before treatment, though longer may be needed. Work in small sections, keep the area wet while working, and rinse dissolved material promptly so it doesn’t redeposit into dry brick.

Safe Cleaning Procedure for Any Brick Stain

1. Identify the stain and find the moisture source if water is involved.
2. Read brick and cleaner manufacturers’ instructions first.
3. Protect nearby plants, windows, and finished surfaces.
4. Test the full procedure on a small, inconspicuous area.
5. Remove loose or large deposits with nonmetallic tools.
6. Pre-wet the target area and masonry below.
7. Apply the lowest effective concentration of an approved cleaner. If acid is required, always add acid to water, never water to acid.
8. Scrub gently with a stiff synthetic or fiber brush, top to bottom; don’t let cleaner dry.
9. Rinse thoroughly with clean water; repeat only as directed.
10. Stop immediately if you see new discoloration, efflorescence, or mortar deterioration.

Wear the protective equipment your cleaner manufacturer specifies, control runoff, and skip metallic brushes, excessive pressure, and cleaning in direct hot sun. Manufacturer compatibility always wins over a generic recipe.