Historic Preservation - Technical Procedures
Removing Organic Stains From Marble
Outdoor Sculpture Manual - Center For Public Buildings
Removing Organic Stains From Marble
REMOVING ORGANIC STAINS FROM MARBLE
THE CLEANING OR REMOVAL OF STAINS FROM STONE MAY INVOLVE THE USE
OF LIQUIDS, DETERGENTS OR SOLVENTS WHICH MAY RUN OFF ON ADJACENT
MATERIAL, DISCOLOR THE STONE OR DRIVE THE STAINS DEEPER INTO POROUS
STONES. USE THE PRODUCTS AND TECHNIQUES DESCRIBED HERE ONLY FOR
THE COMBINATIONS OF DIRT/STAIN AND STONE SPECIFIED.
A. This procedure includes guidance on poulticing marble
stained by organic materials such as food, flowers,
leaves, tea, coffee, bird or animal droppings.
B. Organic stains are typically pinkish-brown in color and
tend to disappear when the offending object has been
removed. This procedure may be used to remove those
stains which remain.
C. Safety Precautions: Bird droppings may expose operators
to the effects of cryptococcosis and histoplasmosis which
endanger the human respiratory system. Public health
authorities should be consulted for appropriate
D. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:
1. Safety Precautions
2. Historic Structures Precautions
4. Quality Assurance
5. Delivery, Storage and Handling
6. Project/Site Conditions
7. Sequencing and Scheduling
8. General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).
E. For additional information on poulticing, see 04455-02-R.
F. For general information on the characteristics, uses and
problems associated with marble, see 04455-01-S.
NOTE: Chemical products are sometimes sold under a common
name. This usually means that the substance is not as pure as
the same chemical sold under its chemical name. The grade of
purity of common name substances, however, is usually adequate
for stain removal work, and these products should be purchased
when available, as they tend to be less expensive. Common
names are indicated below by an asterisk (*).
A. Hydrogen Peroxide (H202): (in a 6% hair bleaching
1. An unstable compound used especially as an
oxidizing and bleaching agent, an antiseptic, and a
2. Other chemical or common names include Peroxide of
hydrogen*; Solution of hydrogen dioxide*;
Superoxol*; (hydrogen peroxide is commonly sold as
a 3% solution; Superoxol is a 30% solution;
Superoxol causes flesh burns; 3% hydrogen peroxide
3. Potential Hazards: TOXIC (when concentrated);
CORROSIVE TO FLESH (gasoline, kerosene and mineral
spirits are each a mixture of compounds from
petroleum, all of which fall within a specified
range of properties); FLAMMABLE (in high
4. Available from chemical supply house, drugstore,
pharmaceutical supply distributor, or hardware
B. White absorbent material (molding plaster, untreated
white flour, white tissue, paper towels, powdered chalk,
talc, fullers earth or laundry whiting)
C. Mineral water
D. Plastic sheeting
E. Clean dry towels for blotting the area after treatment
A. Glass or ceramic container for mixing the solution
B. Wooden utensil for stirring the ingredients
C. Wood or plastic spatula
D. Masking tape
A. Examine the marble surface CAREFULLY to determine the
cause of staining before proceeding with any cleaning
3.02 ERECTION, INSTALLATION, APPLICATION
NOTE: DO NOT USE BLEACH ON DARK COLORED STONES AS THIS WILL
CAUSE THE STONE TO LIGHTEN.
A. Rinse the area to be treated with mineral water.
B. Pour hydrogen peroxide solution in a glass or ceramic
C. Thoroughly moisten the stained surface with this liquid.
Be sure to dampen well beyond the stain.
D. Mix the remaining liquid with the white absorbent
material to form a paste the consistency of oatmeal or
cake icing. (Approximately one pound of paste is needed
for every square foot of surface area to be treated.)
E. Using a wooden or plastic spatula, apply the paste to the
stained surface in layers no more than 1/4 inch thick.
The poultice should extend well beyond the stain to
prevent forcing the stain into previously clean stone.
F. Check the coating for air pockets or voids.
G. Cover the poultice with plastic sheeting and seal with
H. Let set for 48 hours (unless otherwise specified).
I. After set period, dampen the poultice with mineral water.
J. Remove the poultice with a wooden or plastic spatula to
avoid scratching the surface.
K. Again, thoroughly rinse the cleaned area with mineral
water, blot with clean towels and allow the surface to
L. Once the surface has dried completely, check for
remaining residue and repeat the treatment if necessary.
END OF SECTION