That white, powdery mineral substance you see leaching from your stone wall is called efflorescence. When moisture evaporates out of stone, it leaves behind the mineral residue that you're seeing. It's unsightly and should be removed, but the residue won't cause any structural problems. If you remove it and it returns, that means you probably have a problem with water seepage within the walls.
Things You'll Need
- Wire brush
- Protective face mask
- Chemical-resistant gloves
- Muriatic acid
- Spray bottles
- Long-handled masonry brush
- Garden hose
- Phosphoric acid (optional)
- Trisodium phosphate (optional)
Scrub the stone wall with a dry wire brush, loosening the mineral deposits.
Put on chemical-resistant gloves and face shield.
Wet the wall with water using a garden hose or spray bottle if indoors. Protect floors and landscaping with water-resistant drop cloths or tarps and address any spills immediately.
Dilute 1 part muriatic acid with 12 parts water. Slowly add the acid to the water, not vice versa, as a potentially dangerous reaction could occur. Carefully pour the mixture into a spray bottle. Have several spray bottles on hand, as the acid mixture will ruin them after a couple of uses. If you're not comfortable using muriatic acid, you can substitute phosphoric acid or trisodium phosphate (TSP) as the main cleaning agent. Both are sold as commercial cleaning products for stone. Mix with water according to the manufacturer's directions.
Spray the acid mixture onto the wall and allow it to work on the mineral deposits for three to five minutes.
Scrub the mineral deposits with a long-handled masonry brush. Neutralize muriatic acid with a diluted ammonia solution. Rinse thoroughly with clean water and allow the wall to dry.
Observe if all the mineral deposits have been removed. If not, repeat Steps 2 through 6 as often as needed.
Tips & Warnings
- Muriatic acid is extremely corrosive and dangerous. Handle only when wearing chemical-resistant gloves and a face shield.
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