Mortar is the building material that builders use to hold bricks together. Ideally, if any mortar gets on the external surfaces of the bricked area, then the builders will wipe it off before it sets. However, sometimes a builder may be in a hurry or just overlook some wayward mortar, leading to mortar streaks on the bricks of a building or other construction. If you want to remove mortar from bricks once it has dried, you will need to use some pretty serious chemicals in order to get the job done.
Put on your safety gear. Muriatic acid is sold in hardware stores, but it is literally the strongest cleaning agent that can be sold over the counter. It is a real acid, and it can seriously burn you if you use it carelessly. Make sure that you are wearing long sleeves, long trousers, and closed-toed shoes in addition to safety goggles and gloves.
Mix your muriatic acid. Always pour the acid into the water rather than pouring water into the acid. The brand of muriatic acid will determine how you dilute it (usually it is about 10 parts water to 1 part acid). Use a plastic bucket because the acid will corrode metal.
Fill a second bucket with clean water. This will be what you use to scrub the mortar.
Brush the muriatic acid dilution onto the mortared areas of the bricks. It will start to fizz and bubble. Let it sit on the mortar for about 5 minutes, or until it stops fizzing.
Scrub the mortar with the scrub brush. Dip the brush in the clean water. The mortar will come away from the bricks in crumbles without too much effort. Dip your scrub brush regularly into the clear water to add additional water to the mix for rinsing and dilution of the acid.
Hose down the entire area with a great deal of water. This will dilute the acid sufficiently to render it harmless, but you still need to be sure that you use a large volume of water to wash the muriatic acid away entirely or the residue can cause your bricks to weaken over time. While you are rinsing, also rinse off the brushes that you have used.
Do a final rinse with an ammonia and water combination to neutralise the acid entirely. Use a ratio of 1 cup of ammonia per gallon of water. You can mix it in a plastic bucket and then pour it over the area.
Dispose of the scrub brush and paint brush. These should be placed in plastic bags and thrown away. They cannot be reused without posing a threat to your architecture.