How To Clean Brick?
QUICK ANSWER
Wet the brick with water first to prevent staining. Scrub with dish soap and warm water using a stiff-bristle brush in circular motions. For mildew, use 1 cup bleach per gallon of water. For efflorescence (white mineral deposits), use diluted muriatic acid with proper safety precautions.
Brick is durable but porous, so cleaning needs the right approach to lift dirt out of the surface without damaging the brick or mortar. Standard dirt comes off with soap and water; mildew needs bleach; mineral deposits and old stains may need acid. Each situation has a specific method. Here is the approach for exterior brick walls, interior brick (fireplaces, accent walls), and the common stains that need targeted treatment.
Why is brick different from other surfaces?
Brick is fired clay; the surface is porous with thousands of tiny pores that absorb water, stains, and cleaners. The mortar between bricks is even softer and more porous than the brick itself. Aggressive cleaning damages the mortar before the brick. Old brick (pre-1930s) is softer and more porous than modern brick; treat older brick more gently. The mortar is usually weaker than the brick; preserving the mortar is the priority. Pressure washing on high settings can erode mortar within minutes. The right approach uses chemical cleaning plus gentle scrubbing, not high-pressure mechanical cleaning.
What is the basic cleaning method?
Start by wetting the brick thoroughly with a garden hose; pre-wetting prevents the cleaner from soaking deep into the brick and helps lift dirt out. Mix the cleaning solution: 1/2 cup dish soap or 1/4 cup TSP per 1 gallon of warm water. Apply with a stiff-bristle brush (natural bristle or stiff synthetic; never wire brush which scratches the surface and embeds metal particles that rust). Scrub in circular motions. Work in small sections of about 3 by 3 feet. Rinse each section before moving to the next. For exterior walls, work from bottom up; rinse top down to prevent dirty streaks.
How do you remove mildew and biological growth?
Green or black growth (mildew, algae, moss) on shaded brick walls needs bleach. Mix 1 cup household bleach per 1 gallon of water. Apply with a stiff brush; let sit 10 to 15 minutes (don't let dry). Scrub. Rinse thoroughly. For severe biological growth, use an oxygen bleach (OxiClean) solution; gentler on plants and mortar than chlorine bleach. Wear eye protection and gloves; bleach can damage skin and eyes. Cover plants near the wall with plastic. Repeat for stubborn areas. Some old biological growth has actually stained the brick; full removal may require multiple treatments over weeks.
How do you remove efflorescence and other stains?
Efflorescence (white powdery mineral deposits): brush dry first with a stiff dry brush. If still present, use muriatic acid solution (10:1 water to acid). SAFETY CRITICAL: wear acid-resistant gloves, eye protection, respirator; work in ventilated area; never add water to acid (only acid to water); rinse thoroughly. Smoke and soot stains: TSP plus warm water and a stiff brush. Paint stains: commercial paint stripper, scraped off, rinsed.
Brick cleaning starts with the gentlest effective method: dish soap and water for everyday dirt, bleach solution for mildew, acid for efflorescence and the toughest stains. Always pre-wet brick before applying cleaners. Never use wire brushes which damage the surface. Avoid high-pressure washing which erodes mortar. With proper care, brick maintains its appearance for decades; older brick (pre-1930s) needs gentler treatment than modern brick.
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