Things You'll Need
Instructions
Acid Wash
Set up your materials in a well-ventilated area where the acid-water solution can safely drain or be soaked up. Put on your protective gear and fill a spare bucket with water.
Measure one part acid and pour it into nine parts water. Add the acid to the water. Do not add the water to the acid.
Test the solution on an inconspicuous area of the limestone, or on a spare piece, if it's available. Adjust the dilution as necessary.
Paint the diluted acid onto the limestone in a thin, even coat.
Rinse the limestone thoroughly with the power washer almost immediately. The longer you leave on the acid, the more it will wear away the stone. Leaving it on too long can permanently damage the limestone.
Sprinkle baking soda over the entire surface to neutralize any remaining acid mixture. Alternatively, mix the baking soda with water to create a paste and apply it to the limestone. Allow the surface to dry, and then wipe away or rinse off the baking soda.