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TIL a $12 jug of muriatic acid and a Saturday saved my 1920s brick from 40 years of grime
I bought a foreclosure in Dayton last spring and the brick on the front porch was covered in a black crust that a pressure washer alone would not touch. I tried a stiff brush and dish soap first, spent two hours on a 4 foot section, and barely made a dent. Then a guy at the local masonry supply store suggested diluting muriatic acid 10 to 1 and scrubbing it on with a plastic brush, then rinsing fast. I tested it on a hidden patch behind the porch column for 15 minutes to make sure the mortar held up, and it was fine. The whole 30 foot wall took me about 4 hours and the brick went from charcoal gray back to that warm red color. Anyone else used acid on old brick, and did you neutralize with baking soda after or just flush it with a hose?
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kim_patel891d ago
Something a lot of folks miss is what acid does to that black crust on a molecular level. That gunk is mostly carbon and soot from decades of coal smoke, and acid attacks the mineral deposits holding it to the brick, not the carbon itself. So the rinse is what really does the work, and if you let the mix dry on the wall you can end up staining the brick or burning the mortar joints. Heat matters too, that acid will eat faster on a 90 degree day than a cool morning, so mix and rinse smaller sections when it is hot out. Baking soda does neutralize it, but honestly a good long soak with the hose and a scrub keeps it simple if you are quick about it.
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