Copyright Goodheart-Willcox Co., Inc. 254 Section 4 Techniques discussed in the Cleaning Brick section of this chapter, such as wetting the surface with water, applying clean- ing solution, cleaning the surface, and finally rinsing the area with clean water. From the manufacturer’s specifications, determine recommended pressure, size and type of spray nozzle, the distance from wall surface and operation procedures of the equipment. Practice on a section of the wall area that is not as visible. Begin a distance away from the brick, then work closer to the surface as needed to achieve the desired effect. When applying the solution, lower pressure to 30–50 pounds per square foot (psf). Do not allow solution to dry on the wall surface. When the area is clean, rinse the sur- face at a pressure only between 200 and 300 psf, since higher pressures can adversely affect the brick finish. Pressurized cleaning can reduce time, but care must be taken to ensure that the process does not affect the exterior of the brick surface. Abrasive Blasting In abrasive blasting, an abrasive material under air pressure is used to remove unwanted mortar or stains from the surface of brick or other masonry materials. This process may also remove certain finishes on brick, such as glazing, sand finishes, or slurry finishes. It may also roughen the exterior of the brick and change the finished appearance. A gentler abrasive than sand should be used. Examples of softer products are crushed nut shells, dry ice, or baking soda. The cost of abrasive blasting is about the same as acid cleaning. Abrasive blasting is a valuable tool in certain applica- tions, such as for removing persistent stains or mortar. However, the Brick Industry Association recommends that abrasive blasting not be used for brickwork because it may change the appearance of the brick. Particular brick can react with chemicals found in cleaning agents used to wash brick. In certain situations, blasting may be used as a last resort. For best results, use a very low pressure (60–100 psf) and softer materials that will not damage the exterior sur- face of the brick. The secret to successful abrasive blast cleaning is the distance the operator stands from the wall and the manner in which the blast is directed at the brick. Concentrate on hitting the brick rather than the mortar joints. For more information on abrasive blasting, refer to BIA Technical Note 20—Cleaning Brickwork. Safety Note Because of the abrasiveness of the process, a competent person must perform abrasive blasting. Manufacturer’s specifications and SDS documents should be consulted in order to determine equipment operating procedures and necessary PPE, such as a respirator eye protection face mask and protective clothing, footwear, and gloves. Alan Budman/Shutterstock.com Figure 12-68. A pressurized power washer can reduce labor and costs when cleaning brick or other surfaces. Wear appropriate PPE when power washing.