How to Clean Soot From Limestone

Meg Butler

A limestone fireplace makes a beautiful decorative addition to any home. To keep the limestone in good condition, you must clean it regularly. As you burn fires, soot can travel on escaping smoke and cling to the limestone on the front of the hearth. The sooner you clean the soot, the better.

Limestone is quite porous; if soot works its way beneath the surface, it will be more difficult to remove.


For stubborn stains, you can apply a poultice to the limestone. Mix powdered trisodium phosphate or Calgon and bleaching powder with water to make a thick paste. Apply a 1/4-inch thick layer on the limestone with a plastic putty knife. Cover the poultice with plastic wrap. Tape the edges of the plastic wrap down with painter's tape. Punch holes in the plastic to allow the poultice to dry out. Remove the poultice after 48 hours and wash the limestone. Test all cleaning solutions and devices on an inconspicuous spot on the limestone before using them to remove soot.

  1. Place a plastic tarp on the floor around the fireplace to catch any falling soot.

  2. Run the nozzle of a vacuum over the soot on the limestone to remove any loose soot. Alternatively, brush the soot with a dust rag.

  3. Wipe the soot clinging to the limestone with a dry-cleaning soot sponge. Start at the top of the soot damage and work your way down. Wipe with long, horizontal strokes. When the surface of the sponge becomes covered in soot, cut the top layer of the sponge away with a razor blade. Keep wiping until you have removed as much soot as possible.

  4. Mix a solution of water and a pH neutral liquid soap in a bucket. Follow the label's dilution instructions or mix one tsp. of soap per quart of water.

  5. Soak a sponge in the solution and wash the limestone to remove the rest of the soot residue. Wash the limestone from the bottom up; this will prevent streaks of sooty water from washing down the clean surface.

  6. Soak a clean sponge in fresh water and wipe the limestone to remove all soap residue.

  7. Wipe the limestone dry with a towel.