Mortar smeared on a brick wall or walkway can detract greatly from the beauty of the finished product. It may not seem like a problem during the construction process if excess mortar gets onto a few bricks, but once it hardens it can be difficult to remove. It is best to prevent mortar smear while building, or to remove it while it is still wet. If that is not possible, certain chemicals can help remove dried mortar.
Chip or scrape as much of the dried mortar off the brick as possible with a chisel. Be careful not to damage the brick face when doing this.
Wet the area of the brick covered with mortar with a garden hose or sponge. The brick must be wet or else it will absorb the chemical solution.
Mix one part of muriatic acid to 10 parts of water in a bucket. Muriatic acid is similar to hydrochloric acid and can be found in many hardware stores. It is extremely dangerous and can burn your skin, so be careful when handling it.
Apply the muriatic acid solution to the brick mortar using a sponge. Allow the solution to sit for five to 10 minutes. Bubbles should form on the mortar as an indication the muriatic acid is working.
Scrub the mortar using a brush and wash the area covered in the muriatic acid with water. Repeat Step 4 as necessary. It can take several applications of muriatic acid to remove all of the mortar.
Household vinegar can be used as a substitute for muriatic acid on small pieces of mortar that do not contain much sand; however, for larger spots, use muriatic acid.
Use safety gloves, a mask and goggles when handling the muriatic acid. It can cause burns if it comes in contact with the skin, and the fumes are toxic. Try not to get it on bricks that are not covered in mortar, as it could damage or discolour them. Do not apply it to fresh mortar that has not set for at least two weeks.