Brick is porous and holds stains, soot, efflorescence, and mortar residue deep in its surface. The right cleaning method depends on what you’re removing and where the brick is located. Fireplace bricks need soot and smoke stain removal. Exterior brick walls need pressure washing plus chemical treatment for moss, algae, and efflorescence. Mortar stains left from construction require diluted acid treatment. This guide covers all three scenarios.
What You’ll Need
- Stiff-bristle scrub brush (natural or synthetic — not wire on older brick)
- Pressure washer (for exterior brick) or garden hose
- Dish soap or TSP cleaner
- White vinegar or muriatic acid (diluted — for mortar stains)
- Oxygen bleach (for moss and algae)
- Commercial soot remover or trisodium phosphate (TSP) for fireplace brick
- Safety goggles and rubber gloves
- Drop cloth (for interior work)
- Spray bottle
Safety and Precautions
Muriatic acid (hydrochloric acid) is used for mortar removal and efflorescence treatment — it requires full protective equipment: chemical-resistant gloves, safety goggles, and old clothing. Always dilute muriatic acid before use (typically 1 part acid to 10–20 parts water), and always add acid to water, never water to acid. Work in ventilated areas. Wet the brick thoroughly before applying any acid — dry brick absorbs acid too fast and is damaged. Never use muriatic acid on painted brick or antique brick — consult a masonry professional instead. Do not use wire brushes on soft antique brick — they damage the surface permanently.
Cleaning Fireplace Bricks: Soot and Smoke Stains
Protect the Surrounding Area
Lay a drop cloth in front of the fireplace and on the hearth. Remove any fireplace tools, screens, and decorative items. Open a nearby window for ventilation — cleaning products and dislodged soot create fumes.
Dry Brush Loose Soot First
Use a stiff dry brush to sweep loose soot and ash from the brick surface into the firebox. Wear a dust mask — soot is very fine and inhaling it is harmful. This dry pass removes the surface layer before wet cleaning.
Apply TSP Solution or Commercial Soot Remover
Mix TSP (trisodium phosphate) at one tablespoon per gallon of water — or use a commercial fireplace brick cleaner. Wet the brick first with plain water, then apply the cleaning solution generously with a brush or sponge. Let it soak for 10 minutes.
Scrub with a Stiff Brush
Scrub the soot-stained areas vigorously with a stiff bristle brush. Work in sections, scrubbing until the water running off is dark with lifted soot. Pay extra attention to the area directly above the firebox opening where soot concentrates heaviest.
Rinse Thoroughly
Rinse the brick with clean water using a sponge and bucket — you can’t use a hose indoors. Wring and re-rinse the sponge multiple times to remove all TSP or cleaner residue. Allow the brick to dry completely before using the fireplace.
Cleaning Exterior Brick Walls
Sweep and Pre-Rinse
Remove loose debris with a brush and pre-rinse the wall with a garden hose. Wet brick absorbs cleaning solution at a more controlled rate than dry brick.
Apply Oxygen Bleach for Moss, Algae, and Mildew
For biological staining on exterior brick, apply an oxygen bleach solution per product directions. Let dwell for 15–20 minutes, then scrub with a stiff brush and rinse. Oxygen bleach is safe for brick mortar and doesn’t discolor the brick the way chlorine bleach can.
Pressure Wash at 1,200–2,000 PSI
For general grime on exterior brick, pressure washing at 1,200 to 2,000 PSI with a 25-degree nozzle removes accumulated dirt and biological growth efficiently. Keep the nozzle 12–18 inches from the surface. Do not use high-pressure settings on older, softer brick — high pressure can damage the brick face and blow out mortar joints.
Treat Efflorescence
White powdery deposits on exterior brick are efflorescence — mineral salts carried to the surface by water. Dry-brush first, then apply a diluted vinegar solution (equal parts water and white vinegar) or a commercial efflorescence remover. Scrub and rinse. For heavy efflorescence, a diluted muriatic acid solution is more effective — see the mortar stain removal section below for acid safety protocol.
Removing Mortar Stains from Brick
Dried mortar smears from bricklaying or repointing work require acid to dissolve. Use muriatic acid or a commercial masonry acid cleaner.
Saturate the Brick with Water
Thoroughly wet the brick before applying acid. This prevents the acid from being absorbed too deeply into the brick pores. The surface should be visibly wet before acid contact.
Mix Diluted Muriatic Acid
Wearing chemical-resistant gloves and goggles, mix one part muriatic acid with ten parts water in a plastic (not metal) bucket. Always pour acid into water — never water into acid. The resulting solution will dissolve mortar smears on contact.
Apply with a Stiff Brush
Apply the acid solution to the mortar-stained areas using a stiff acid-resistant brush. Let it fizz and react for 2–5 minutes. The acid dissolves the calcium carbonate in the mortar.
Scrub and Rinse Immediately
Scrub the area to loosen dissolved mortar residue, then rinse thoroughly with large amounts of water. Flush the area repeatedly — acid left in brick pores continues to react and can damage the brick over time. Rinse until no fizzing occurs when fresh water is applied.
Pro Tips
- Test in a hidden corner: Brick varies enormously in hardness, porosity, and age. Test any cleaning chemical on a hidden area first — especially acid on antique or reclaimed brick.
- Don’t use muriatic acid on painted brick: Acid dissolves paint and can discolor brick permanently. For painted brick, use TSP or an alkaline masonry cleaner instead.
- Seal exterior brick after cleaning: A masonry sealer applied after cleaning reduces future efflorescence, slows biological growth, and makes future cleaning much easier.
Frequently Asked Questions
How do I remove soot from light-colored fireplace brick?
Use cream of tartar mixed with water into a paste, applied to the stained area. Let sit for 10 minutes, scrub with a stiff brush, and rinse. For stubborn soot, TSP solution is more powerful. Avoid bleach on light brick — it can create yellowing.
Can I use a pressure washer on fireplace brick?
Only on exterior-facing fireplace brick or brick surround if it’s accessible and water can drain freely. Never pressure wash inside a firebox or in an indoor fireplace — water damage to the firebox and surrounding structure is a serious risk. Indoor fireplace brick must be wet-cleaned by hand with sponges.
How do I get rid of white stains on exterior brick?
White staining on brick is almost always efflorescence. Treat with diluted white vinegar, a commercial efflorescence remover, or very diluted muriatic acid (1:20 ratio) for severe cases. Address the moisture source — cracks in mortar, poor drainage, or missing flashing — or the efflorescence will return.
Is bleach safe on brick?
Chlorine bleach can discolor some brick types and degrade mortar with repeated use. Oxygen bleach is a safer alternative for biological staining on brick. If you use chlorine bleach, dilute significantly (1/4 cup per gallon) and rinse promptly and thoroughly.
How do I clean mortar off new brick without acid?
Fresh mortar (still within 24–72 hours of application) can often be removed mechanically — scrape with a wooden or plastic scraper and scrub with a stiff brush and water. The longer you wait, the harder mortar becomes, eventually requiring acid to dissolve it. Address fresh mortar smears promptly to avoid needing acid treatment.
Conclusion
Brick cleaning success comes down to matching the method to the problem: TSP or soot remover for fireplace brick, oxygen bleach for exterior biological growth, and diluted acid for efflorescence and mortar stains. Wet the brick before applying any cleaner, rinse thoroughly, and seal exterior brick afterward for long-term protection. For other masonry surfaces, see our guide on how to clean a slate hearth — natural stone maintenance shares similar principles to brick care.
