How to Clean Natural Stone Furniture

Natural stone outdoor furniture, such as tabletops and benches, is subject to stains from food, wine and molds that can grow in spots of permanent shadow. To keep your natural stone furniture looking its best, follow these cleaning tips, and treat stains as soon as they happen.

Tools and Equipment You Will Use:

  • scrub brush with nylon bristles
  • garden hose
  • neutral pH cleanser for stone
  • muriatic acid
  • natural stone sealer, new paint brush
  • drop cloths, plastic bucket
  • metal bowl for the muriatic acid
  • eye goggles
  • gloves
  • wear old loose clothing while cleaning

Step 1:    Clear the Area to be Cleaned

Move away all plant containers, patio umbrellas, chairs and cushions. Put drop cloths over nearby shrubbery and patio stones under the furniture to prevent splashes of cleaning products from harming them.

Step 2:    Soak Porous Stone with Water

With the garden hose, apply water to the stained area until it beads up on the surface of both the stone and any grout or mortar binding it. This prevents the stone from absorbing dirt that you loosen from the surface.

Step 3: Scrub with pH Neutral Cleansing Detergent

Using the scrub brushes, put the cleanser on specific stains like wine, mold and mildew, and scrub vigorously to remove the stain. Fill the bucket with clean water and splash the area to rinse it. Avoid letting dirty water run over clean, dry stones.

Step 4:    Treat Deeply-Set Stains with Muriatic Acid

Mix the muriatic acid with water in a metal container according to the package directions, and put it only on the stained spot. Muriatic acid will bleach whatever it touches, so keep it away from your skin, eyes and hair.  Scrub with the brush until the stain disappears. Rinse the spot completely with the garden hose to remove any lingering acid solution.

Step 5: Do an Overall Cleaning of the Furniture

Deluge the furniture with water from a pressure washer, taking care not to direct pressure toward grouted or mortared sections. Wipe all the surfaces with the pH neutral cleaner and rinse well.

Step 6:    Apply Stone Sealer as Needed

To prevent new stains in the future, seal the edges of benches and tabletops-where people most often put their hands, food or drinks-with a natural stone sealer. You can find these at building supply and hardware stores. The dealer where you purchased your furniture will be able to recommend a stone sealer that works effectively with their stone products.

Step 7:    Prevention of Stains

Use placemats on stone tabletops when serving food and beverages. Cover the table or bench with a waterproof drop cloth to avoid marking from acid rain.

Step 8:    Avoid These Cleaning Products on Natural Stone

Under no circumstances try to clean natural stone furniture with any of these products: abrasive cleansers, metal scouring pads, those containing chlorine bleach, spray cleaners for glass, ammonia-based cleaners, vinegar at any strength, and cleaners with lemon or orange oils. They will scratch, discolor, or leave worse stains than those you are trying to remove.