Historic Preservation - Technical Procedures
- Removing Etch Marks In Marble
- Procedure code:
- Outdoor Sculpture Manual - Center For Public Buildings
- Last Modified:
- Removing Etch Marks In Marble
- Last Modified:
REMOVING ETCH MARKS IN MARBLE
THE CLEANING OR REMOVAL OF STAINS OR BLEMISHES 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 PROBLEM AND STONE
A. This procedure includes guidance on removing etch marks
in marble. The removal process requires two steps:
1. Removal of the stain or substance causing the etch
marks by applying a poultice or "nest". Either
method is acceptable, and both are included in this
2. Repolishing the surface once the stain is removed
(see 04455-02-P "Repolishing Marble" for
B. Etching involves alteration of the surface reflection,
especially a change or reduction in the specular
character or gloss of a highly polished surface.
C. Etch marks are typically caused by certain acids left on
the finish of stone surfaces. These blemishes can be
caused by substances such as wine, beer, fruit juices,
vinegar, tomato products, mustard, carbonated beverages,
ink or salad dressing. Acid containing substances, such
as these, will dissolve portions of the stone,
particularly calcareous stones such as marble or
limestone. The exposed surface below the affected areas
will not be polished, but will be natural stone and
therefore will appear as a non-reflective area.
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 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. Common laundry bleach or a 6% solution of hydrogen
peroxide as the active agent in the poultice:
Hydrogen Peroxide (H202):
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
A. Examine the marble surface CAREFULLY to determine the
cause of the problem before proceeding with any cleaning
3.02 ERECTION, INSTALLATION, APPLICATION
A. The Poultice Method:
NOTE: DO NOT USE BLEACH ON DARK COLORED STONES AS THIS
WILL CAUSE THE STONE TO LIGHTEN.
1. Rinse the area to be treated with mineral water.
2. Pour hydrogen peroxide solution in a glass or
3. Thoroughly moisten the stained surface with this
liquid. Be sure to dampen well beyond the stain.
4. 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
5. 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.
6. Check the coating for air pockets or voids.
7. Cover the poultice with plastic sheeting and seal
with masking tape.
8. Let set for 48 hours (unless otherwise specified).
9. After set period, dampen the poultice with mineral
10. Remove the poultice with a wooden or plastic
spatula to avoid scratching the surface.
11. Again, thoroughly rinse the cleaned area with
mineral water, blot with clean towels and allow the
surface to dry.
12. Once the surface has dried completely, check for
remaining residue and repeat the treatment if
B. The "Nest" Method:
1. Pour a moderate amount of mineral water into the
2. Add a small amount of molding plaster to the water.
3. Stir the mixture, continue adding plaster and
stirring until the solution has the consistency of
4. Mold the paste like a bird's nest and place it on
the stain. Be sure the mold covers the entire
stain and parts of the unsoiled stone surrounding
the entire stain.
5. Allow the nest to dry (approximately 30 minutes).
6. Pour some hydrogen peroxide solution into the nest
and allow to set for about three hours.
7. After the set period, remove the mold with a wooden
scraper (to avoid scratching the surface).
8. Wash the surface thoroughly with mineral water.
9. Blot the surface and allow it to dry completely.
10. If residual staining remains, repeat the treatment
until the entire stain has been removed.
NOTE: Either method of removing etch marks should be followed
by repolishing of the stone surface (see 04455-02-P
END OF SECTION