Clean stains from a marble countertop by applying a specially prepared poultice to wick the stain and then applying a new sealant. The poultice removes the stain from the stone pores while the sealant protects the marble from further staining.
- Prepare the poultice
Prepare a poultice to absorb the stain from the open pores of the marble with a mixture dependant on the type of stain present. Use flour for the poultice base, and then add hydrogen peroxide for food stains, mixing the two until the flour is the consistency of smooth peanut butter. Substitute dishwashing liquid for the hydrogen peroxide for use with oil-based stains, household bleach for mold or mildew or sodium hydrosulfate for rust stains.
- Apply the poultice
Spread a 1/4-inch thick layer of the poultice over the stain using a plastic putty knife. Extend the coverage of the poultice 1/4-inch past the edges of the stain. Cover the poultice with a sheet of plastic wrap attached to the surface of the countertop with painter's tape around the edges. Poke several small holes in the plastic wrap to allow air to flow over the poultice. The plastic prevents the active ingredient in the poultice from drying out before being allowed to act on the stain, while the circulating air allows it to pull out the stain as it slowly dries. Let the poultice sit in place for 24 hours to be absorbed into the stone fully.
- Remove the poultice
Remove the plastic wrap, and then scrape away the poultice with the plastic putty knife. Wipe the surface clean with a dry towel. Allow the countertop to dry after removing the poultice, and then examine it for further signs of the stain. If staining remains, repeat the process as needed until it disappears.
- Seal the marble
Seal the marble by applying a paste wax coating to the area where the poultice was applied. The sealant protects against future penetration of the stone by sealing off the open pores in the marble.