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How to Acid Wash Fireplace Rocks

Claudia Henning

The beauty of a stone fireplace always draws guests to gather around it. Over time soot buildup makes the fireplace look dirty and uncared for. This can be an embarrassing problem. Scrubbing with soap and water alone will not remove the residue.

Make your fireplace stones gleam like new with phosphoric acid masonry cleaner and water. Even with the worst buildup, this do-it-yourself cleaning is manageable in two hours or less by most homeowners.

  1. Mix one bucket of warm water with half a cup of liquid detergent. Use a scrub brush and vigorously scrub each stone. Use rags dampened with clear water to rinse.

  2. Mix the recommended amount of phosphoric acid masonry cleaner with water. Different brands may require a different mixture, so follow directions carefully. Use a gloved hand to scrub the stones with the mixture. Allow the acid cleaner 10 to 15 minutes to strip away the residue on the stones. Rinse with clear water using the rags.

  3. Mix a spray bottle with warm water and one fourth cup of baking soda. Liberally spray the mixture on the surface of the stones. Scrub with a sponge. Rinse with water and let the stones air dry.

  4. Tip

    Cover surrounding floors and walls with a plastic drop cloth to protect from the caustic cleaner. Learn more about various fireplace stone at fireplaces-fireplaces.com.


    Wear safety glasses and gloves when working with phosphoric acid cleaner.

    Keep the area well ventilated from fumes.