There are two reasons to clean masonry brick: either you are cleaning a new brick construction or you have decided to clean old brick that has become soiled or moulded. The method for cleaning brick will not change depending on whether the bricks are old or new. However, there are several different methods for cleaning brick, depending on the amount and type of soil to be removed.
Determine the desired approach to cleaning brick. There are several ways to clean masonry brick. Powder detergent is one mixture that can safely clean brick. Brick cleaning solutions that are designed to clean brick have a mixture of acid and detergents that will do a good job as well. Using a pressure washer is an approach that often will yield clean brick without the use of any chemicals. As a last resort, muriatic acid can be used but with caution.
Mix washing powders and water to get a mild detergent that will clean most masonry bricks. Using a 22.5 litre (5 gallon) bucket, mix 1 scoop of washing powder with about 15.75 litres (3 1/2 gallons) of water. Using the acid brush and handle, soak the brick with the detergent mixture and scrub vigorously. While the detergent is allowed to sit for 20 minutes, scrub any stubborn areas with a wire brush, wash the area once more with the acid brush, and spray off with a garden hose.
Mix brick cleaner and water together for a stronger application. Brick cleaners, such as Sure Klean, are often designed specifically to clean brick. They are a little more caustic, however, depending on the severity of the soiled brick, they can provide a more pleasing finish. Brick cleaner comes in 4.5 litre (1 gallon) jugs, or, for larger jobs, 22.5 litre (5 gallon) jugs. Follow the same procedure as in the washing powder mixture; however, allow no more than 15 minutes for setting.
Clean the masonry brick with a pressure washer. Pressure washers can deliver water pressure of 17,237 kPa (2,500 psi) or more. A pressure washer will clean effectively and safely. You may rent a pressure washer from your local tool rental shop. The shop assistant will also instruct you on the use of a pressure washer.
Muriatic acid should only be used as a last resort when the soil on the brick is stubborn. Muriatic acid will remove almost anything, including the brick face. Never leave the acid mixture on the surface longer than five minutes. Fill a 22.5 litre (5 gallon) bucket about 3/4 full and add the acid. Follow the instructions on the acid container for the correct mixture. Use an acid brush to vigorously scrub the brick, allow to set for no more than five minutes, scrub with a wire brush and rinse off with a garden hose.
Always wear eye goggles, a dust mask, rubber gloves, a long-sleeved shirt and trousers. Chemicals can burn the skin, eyes and lungs and should be avoided if possible. Also, loose chunks of brick can blow into your eyes if you are pressure washing. Remember to be safe when performing any of the above procedures.