How To Clean Brick; It's actually quite simple, when mortar or grout is splattered on the face, it can be quite ugly. The final appearance of a brick masonry wall depends primarily on the attention you give the masonry surfaces during construction and cleaning.
Note the during construction part, this is greatly overlooked as masons smear the mortar all over the face of the brick, there is actually a method in doing this clean, refer to masonry videos. But we all had to learn sometime; in the event that this does happen, here are some important points to remember when you clean brick masonry.
A chemical analysis of efflorescent salts in the Southern California area (1) reveals that they are principally alkalies of Sodium Sulfates (Na3S04) and Potassium Sulfates (K2S04). These are the main soluble salts to be concerned with in Southern California since these are 90% of the efflorescence found in this area. These alkali sulfates appear because they exist somewhere within the masonry wall, either in the brick, the mortar, or the grout, or possibly a combination of these three.
These alkalies combine with sulfates from the masonry to form sulfate salts. The alkali sulfates in the wall are dissolved by water into a solution which then moves through the natural pores in the masonry. The solution migrates to the surface of the wall where the water evaporates, depositing the salts on the wall and generating the white powdery scum we know as efflorescence. If you are learning How To Clean Brick keep reading and follow the links for more valuable info in your brick cleaning venture. High Pressure Cleaning How to Clean Brick when that whit powder starts to form. When efflorescence is light, you can remove it with water and a brush. In more severe cases, wet down the wall and scrub it with SAKRETE Concrete & Asphalt Cleaner, available in 1 qt. bottles, or white vinegar. Flush the area several times with water when finished. Be careful to protect shrubs and bushes from vinegar wash.
If block or brick is just too stained and you have tried everything you can think of, removal of the block or brick is the last option but very possible. Tools needed are a right angle grinder, 4" will work with a diamond or masonry carborundum blade sold at most any hardware store, hammer, chisel, brick trowel, bag of premixed mortar, dye color if needed, usually purchased at a building supply or lumbar yard, block or brick to match existing, mud board or bucket to mix mortar, brush, a groover or rake to take care of the joints.
Take the grinder and grind 2" into the bed and vertical joints, careful to not grind block or brick next to the stained one. After grinding, carefully chisel out the face of the block or brick removing 2" deep so you can get some mortar behind the face of the new brick that you will cut off your new material. Cut the face off the new brick or block 1-1/2 inches. After cleaning all extra mortar off the block, spray it out with water so the block will be clean and it will soak in the moisture and allow the mortar you place on the face brick to cure slower, it will match the curing process of when it was originally set keeping the mortar joint the same color. Tool or rake as necessary brush joint and retool or match existing joint.