What Cleans Mortar Off Flagstone?

Sugar Water

• Applying sugar water to mortar residue helps dissolve mortar to the point where it can be removed easily with a scrub brush. Sugar acts as a dissolvent when added to water, applied to substances and allowed to sit for several minutes. Add a cup of sugar to a gallon of water in a large bucket. Allow the sugar to dissolve in the water before dipping a sponge into the sugar water. Let the sugar water sit for 20 minutes on the flagstone before scrubbing the softened mortar with a scrubbing pad. Use a power hose to spray the flagstone clean after removing as much of the mortar as you can.

Acid Wash

• Homeowners can purchase an acid wash specifically designed for use on flagstone that is safe for the flagstone and the environment. Before applying the acid wash, scrape off any larger quantities of remaining mortar with a wire brush. Apply the acid wash only to areas with mortar and allow it to sit for approximately 10 minutes. Use the wire brush to scrape away loosened mortar while the acid wash is still on the flagstone. Once you have most of it off, spray the areas with a strong hose until the flagstone is clean.

Washing Powder

• If the mortar smears are light, without many thick clumps, you can clean the flagstone with a mixture of water and washing powder. Prior to washing the flagstone, soak the affected flagstone with a strong hose. Let the water sit for five minutes before washing. Combine a scoop of the washing powder with 5 gallons of water in a large bucket. Stir the mixture until it creates a large amount of suds. Use a stiff brush and scrub the flagstone, using the suds from the washing powder and water. Let the suds sit on the flagstone for approximately five minutes. If needed, reapply the soapsuds to the flagstone until all the mortar residue is gone. Rinse the flagstone with the strong hose until clean.

Considerations

• When removing the mortar residue with the acid wash, always wear a face mask and gloves for protection. Wipe off excess mortar when it first happens before it has a chance to dry. When using products you've never used before, read all directions on the back of the packaging.