Poultice materials include kaolin, fuller’s earth, whiting, diatomaceous earth, powdered chalk, white molding plaster, and 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. Premixed poultices that require adding only water are also available from stone maintenance supply companies.
Preparing & Applying 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 the chemical and let drain. Don’t let the liquid drip.
3. Apply the poultice to the stained area about 1/4″ to 1/2″ thick and extend the poultice beyond the stained area by about one inch. Use a wood or plastic spatula or scraper to spread the poultice evenly.
2. Prepare the stain area. Wet the stained area with distilled water.
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 five or more applications for difficult stains.
8. If the surface (calcareous stones) is etched by the chemical, apply polishing powder and buff with a polishing pad recommended by the polishing powder manufacturer.
It is possible that some stains may never be completely removed. Consult with a stone professional to determine additional steps that might be taken.