Substance to be Removed

Acid-Sensitive

Limestone, Marble, Polished Granite, Glazed Brick

Non-Acid-Sensitive

Sandstone, Slate, Granite, Unglazed Brick, Concrete

Dirt and/or Pollutant Crusts

Water wash

Water and non-ionic detergent

Ammonia

Water wash

Water and non-ionic detergent

Hydrofluoric acid

Paint

(Oil, latex, acrylic coating, vinyl, epoxy, urethane-type coatings)

Ammonia, potassium hydroxide or TSP

Methylene chloride

Ammonia, potassium hydroxide or TSP

Methylene chloride

Whitewash and Cementations Paints

Acetic acid or very weak solution of hydrochloric acid

Acetic acid

Hydrochloric acid

Stains - Iron (Rust)

Poultice with:

Sodium citrate in water + glycerin or Ammonium oxalate

Poultice with:

Oxalic acid or orthophosphoric acid + sodium salt of EDTA in water or Dilute hydrofluoric acid

Stains - Copper

Poultice with:

Ammonium chloride or

Aluminum hydroxide + ammonia

Poultice with:

Ammonia (+ EDTA) or

Dilute hydrofluoric acid

Stains - Plant and Fungal

(lichens, algae, moss, fungi)

Dilute ammonia

Hydrogen peroxide

Sodium hypochlorite (HCL)

Dilute ammonia

Bleaches

Hydrogen Peroxide

Sodium hypochlorite (HCL)

Stains - Graffiti

(felt-tipped marker)

Organic solvent or alkaline paint remover

Lacquer thinner or acetone

Methylene chloride

Organic solvent paint remover

Lacquer thinner or acetone

Methylene chloride

Salt/Efflorescence

Water wash

Water (poultice)

Water wash

Water (poultice)

Bird Droppings

Water wash

Water + non-ionic detergent

+ chelating agent such as EDTA

Water wash

Water + detergent

+ chelating agent such as EDTA

Hydrofluoric acid