Algae and mildew can build up on brick over a winter season, or if the brick is exposed to moisture and shade. Algae discolors the brick and can make the surface look prematurely old. Cleaning brick off algae is not difficult, but the choice of chemical cleaners is important, especially if the brick is outside. Using improper cleaners can lead to the death of the surrounding vegetation. Oxygen bleach will kill the algae without harming the brick, mortar or plant life.
Fill a 5-gallon bucket with warm water. Add powdered oxygen bleach at the rate directed on the package. Stir with a wooden stick or paint stirrer until the bleach dissolves.
Pour the bleach solution onto the brick. If you are cleaning a brick wall, dip a sponge into the solution and wipe down the brick until it is soaked. Let the bleach sit for 10 minutes.
Scrub the brick with a street broom or a stiff-bristle scrub brush until the algae is gone. Rinse the brick with a garden hose and let it air-dry.