Making and Using a Poultice

A poultice is a liquid cleaner or chemical mixed with a white absorbent material to form a paste about the consistency of peanut butter. The poultice is spread over the stained area to a thickness of about ¼ to ½ inch with a wood or plastic spatula, covered with plastic wrap, taped down, and left to work for 24 to 48 hours. The liquid cleaner or chemical will draw out the stain into the absorbent material. Poultice procedures may have to be repeated to thoroughly remove a stain, and some stains may never be completely removed.
Poultice materials include kaolin, fuller's earth, whiting, diatomaceous earth, powdered chalk, white moulding plaster, flour, or talc. Approximately one pound of prepared poultice material will cover one square foot. Do not use whiting or iron-type clays such as fuller's earth with acid chemicals. The reaction will cancel the effect of the poultice. A poultice can also be prepared using white cotton balls, white paper towels or gauze pads.

Cleaning Agents or Chemicals

Oil-based stains: Poultice with baking soda and water OR one of the powdered poultice materials and mineral spirits.
Organic Stains: Poultice with one of the powdered poultice materials and 12% hydrogen peroxide solution (hair bleaching strength) OR use acetone instead of the hydrogen peroxide.
Iron Stains: Poultice with diatomaceous earth and a commercially available rust remover. Rust stains are particularly difficult to remove.
Copper Stains: Poultice with one of the powdered poultice materials and ammonia. These stains are difficult to remove.
Biological Stains: Poultice with one of the poultice materials and diluted ammonia OR bleach OR hydrogen peroxide. DO NOT MIX BLEACH AND AMMONIA! THIS COMBINATION CREATES A LETHAL AND TOXIC GAS!
Applying and Using the Poultice:

  1. Prepare the poultice. If using powder, mix the cleaning agent or chemical to a thick paste the consistency of peanut butter. If using paper, soak in the chemical and let drain. Don't let the paper drip.
  2. Wet the stained area with distilled water.
  3. Apply the poultice to the stained area about ¼ to ½ inch thick and extend the poultice beyond the stain by 1 inch. Use a wood or plastic scraper to spread the poultice evenly.
  4. Cover the poultice with plastic and tape the edges to seal it.
  5. Allow the poultice to dry thoroughly, usually about 24 to 48 hours. The drying process is what pulls the stain out of the stone and into the poultice material. After about 24 hours, remove the plastic and allow the poultice to dry.
  6. Remove the poultice from the stain, rinse with distilled water and buff dry with a soft cloth. Use the wood or plastic scraper if necessary.
  7. Repeat the poultice application if the stain is not removed. It may take up to five applications for difficult stains.
  8. If the surface is etched by the chemical, apply polishing powder and buff with burlap or felt buffing pad to restore the surface.

TABLE OF CONTENTS

1.         Care & Precautions
2.         Cleaning Procedures & Recommendations
3.         Know Your Stone
4.         Spills and Stains
5.         Making and Using a Poultice
6.         Do's and Don'ts