Whether you have a few paint drips or some overspray to remove from brick, or you want to bring a dingy painted brick wall back to its former glory, you'll need to use the best product for the job. Brick is a very porous surface; paint tends to soak in and can be stubborn to remove. You'll probably need to use chemicals, but there are now some relatively nontoxic paint removers on the market.
Trisodium phosphate (TSP)
Trisodium phosphate is a strong cleaner. It can soften and remove water-based (latex) paint if mixed in a strong solution with hot water. Mix about 1 cup of TSP per gallon of hot water and apply it to the brick. Scrub the paint with a wire brush or paint scraper, rewetting the brick frequently while you work. Since TSP comes in several forms--powdered, liquid and phosphate-free--read the label directions for mixing instructions. TSP will be useful for removing drips and light overspray, although it's not strong enough to remove several layers of paint on a brick wall.
Solvent-Based Paint Removers
Methylene chloride is the most common type of solvent-based paint remover. It's a strong chemical and effective for removing layers of paint from brick, although government watchdog agencies like the Environmental Protection Agency (EPA) warns that it may cause cancer and organ damage. If you use it, make sure you're working in a well-ventilated area and use fans and open windows when stripping paint from indoor brick. There are several other, less commonly used solvent-based paint removers, and all are potentially harmful to both you and the environment.
Caustic Paint Removers
Lye (sodium hydroxide) is the active ingredient in some less-common paint removers. Although lye can discolour wood and some metal surfaces, it's effective on brick and masonry. However it can cause severe chemical burns to skin, and you'll need to wear protective clothing: goggles, heavy gloves, trousers and a jacket that is resistant to caustic alkalis. Like methylene chloride, caustic paint remover is effective for removing several layers of paint at a time.
Citrus Paint Removers
Citrus-oil (d-limonene) paint removers are less toxic than solvent-based or caustic removers, although they are not completely safe. Michael McCann, PhD, CIH, who has written several books on materials safety for painters, warns that the citrus smell can be tempting to children and will make anyone ill if ingested. Citrus paint remover is effective for removing some graffiti and light paint applications from brick, although it may not be strong enough for stripping multiple layers.
Sandblasting paint from brick is a fast removal method. Besides sand, other products include baking soda, ground glass or walnut shells and corn cobs. While effective, it can permanently damage the underlying brick, and the National Park Service does not recommend it for buildings of historical importance.