Poultice Method
The poultice method is a highly effective technique for drawing out deep-seated stains from natural stone. A poultice is a paste-like mixture of an absorbent material and a chemical cleaning agent. The drying process of the poultice pulls the stain from the stone into the absorbent material. 1. Prepare the Poultice: Mix the chosen absorbent material with the appropriate cleaning agent to form a thick paste, similar in consistency to peanut butter.
- Materials for Poultice:*
- Absorbent Materials: Kaolin, fuller's earth, whiting, diatomaceous earth, powdered chalk, white molding plaster, talc, or even white cotton balls, paper towels, or gauze pads.
- Cleaning Agents: Determined by the stain type (see below).
- Procedure:*
Stain Types and Removal
Identifying the type of stain is the first and most critical step in effective removal. Consider the stain's location, color, shape, and what activities occur in the surrounding area. heavy liquid paint strippers. Always follow manufacturer’s directions, ensure ventilation, and protect yourself. Use wood or plastic scrapers.
- Oil-Based Stains (Grease, Tar, Cooking Oil, Milk, Cosmetics): These stains darken the stone and require chemical dissolution. Clean gently with a soft, liquid cleanser containing bleach, household detergent, ammonia, mineral spirits, or acetone. For poultices, use baking soda and water, or a powdered poultice material with mineral spirits.
- Organic Stains (Coffee, Tea, Wine, Fruit, Tobacco, Food, Urine, Leaves, Bird Droppings): May cause a pinkish-brown stain. Outdoors, sun and rain can naturally bleach these out. Indoors, clean with 12% hydrogen peroxide (hair bleaching strength) and a few drops of ammonia. For poultices, use a powdered poultice material with 12% hydrogen peroxide solution or acetone.
- Metal Stains (Iron, Rust, Copper, Bronze): Iron/rust stains are orange to brown, while copper/bronze stains appear green or muddy-brown. These are particularly difficult and often require a poultice. For iron stains, use diatomaceous earth with a commercial rust remover (e.g., Iron Out). For copper stains, use a powdered poultice material with ammonia. Deep-seated metal stains may be permanent.
- Biological Stains (Algae, Mildew, Lichens, Moss, Fungi): Clean with a diluted solution of 1/2 cup ammonia, bleach, or hydrogen peroxide per gallon of water. Never mix bleach and ammonia.
- Ink Stains (Magic Marker, Pen, Ink): On light-colored stones, clean with bleach or hydrogen peroxide. On dark-colored stones, use lacquer thinner or acetone.
- Paint: Small amounts can be removed with lacquer thinner or carefully scraped with a razor blade. Heavy paint requires commercial
- Water Spots and Rings (Hard Water Accumulation): Buff with dry 0000 steel wool.
- Etch Marks: Caused by acids. These are not stains but surface damage. Once any accompanying stain is removed, use marble polishing powder and buff with a damp cloth or low-speed power drill. For persistent or deep etching, professional restoration is recommended.
- Efflorescence (White Powder): Caused by mineral salts. For new installations, dust mop or vacuum. Do not use water. If persistent, contact an installer to address moisture source.
- Scratches and Nicks: Slight surface scratches can be buffed with dry 0000 steel wool. Deeper scratches require professional repair and repolishing.