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Poulticing Rust Stains From Limestone And Marble
POULTICING RUST STAINS FROM LIMESTONE AND 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.
PART 1---GENERAL
1.01 SUMMARY
A. This procedure includes guidance on removing rust stains
from limestone and marble by poulticing using different
chemical solvents or by using a paste containing a
commercial rust remover.
NOTE: THIS PROCEDURE MAY ALSO BE USED FOR REMOVING RUST
STAINS FROM BRICK MASONRY.
B. Metallic stains from iron or steel have the appearance of
rust. This type of staining is often caused by the run-off
from flashing, gutters, statuary and fasteners. The source of the rusty runoff should be determined and cause abated. Cleaning should be undertaken after rectifying deficiencies causing the rusting. Following cleaning, the surfaces should be inspected after several episodes of precipitation to confirm success of repairs or other treatments.
C. 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
3. Submittals
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).
D. For additional information on poulticing, see 04455-02-R.
E. For general information on the characteristics, uses and
problems associated with limestone, see 04460-01-S; for
marble, see 04455-01-S.
PART 2---PRODUCTS
2.01 MANUFACTURERS
A. ProSoCo, Inc.
www.prosoco.com
2.02 MATERIALS
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. For Normal Treatment:
1. Sodium Citrate (appears like enlarged salt
granules):
a. Other chemical or common names include Citrate
of soda*.
b. Available from chemical supply house, rug
store or pharmaceutical supply distributor.
2. Glycerine:
a. Other chemical or common names include
Glycerol; Glyceryl hydroxide; Glycyl alcohol;
1,2,3-propanetriol; Propenyl alcohol.
b. Potential hazards: FLAMMABLE.
c. Available from chemical supply house, drug
store or hardware store.
B. For Light Stains:
1. Oxalic acid (COOH)2 or (H2C2O4):
a. A poisonous strong acid that occurs in various
plants as oxalates and is used especially as a
bleaching or cleaning agent and in making
dyes.
b. Other chemical or common names include
Ethanedioic acid.
c. Potential Hazards: TOXIC; CORROSIVE TO
CONCRETE, STEEL, WOOD OR GLASS.
d. Available from chemical supply house, dry
cleaning supply distributor, drugstore or
pharmaceutical supply distributor, hardware
store, or photographic supply distributor (not
camera shop). (Often sold under a
manufacturer's brand name; the chemical name
may appear on the label.)
C. For Stubborn Stains:
1. Sodium Hydrosulfite (NaHSO4):
a. Other chemical or common names include Sodium
Hyposulfite; Sodium Subsulfite; Sodium
Thiosulfate; Antichlor*; Hypo*; Hyposulfite of
soda*.
b. Potential Hazards: TOXIC; CORROSIVE TO
CONCRETE, STEEL, WOOD OR GLASS.
c. Available from chemical supply house, dry
cleaning supply distributor, drugstore or
pharmaceutical supply distributor,
photographic supply distributor (not camera
shop), stone dealer, or water and sanitation
supply distributor.
-OR-
Sodium Hypochlorite:
a. Other chemical or common names include
Bleaching solution*; Household bleach*;
Laundry bleach*; Solution of chlorinated
soda*.
b. Potential Hazards: CORROSIVE TO FLESH.
c. Available from chemical supply house, grocery
store or supermarket, hardware store or
janitorial supply distributor.
NOTE: A POULTICE USING EITHER OF THESE CHEMICALS
SHOULD ONLY BE LEFT ON THE SURFACE FOR 30 MINUTES
PER APPLICATION AND AFTER THE REMOVAL, THE SURFACE
SHOULD BE IMMEDIATELY FLUSHED WITH A SODIUM CITRATE
SOLUTION. (This treatment may cause some etching
of polished surfaces but can be corrected by
repolishing - see 04455-02-P "Repolishing Marble").
-OR-
Commercial rust remover, such as "Sure Klean
Ferrous Stain Remover (ProSoCo, Inc.), or approved
equal.
NOTE: THIS POULTICE APPLICATION SHOULD ONLY SET
FOR 24 HOUR PERIODS AS OPPOSED TO TYPICAL 48 HOUR
SET PERIOD.
C. White absorbent material (molding plaster, untreated
white flour, white tissue, paper towels, powdered chalk,
talc, fullers earth, acid-free paper pulp or laundry
whiting).
D. Plastic sheeting
E. Mineral water
2.02 EQUIPMENT
A. Glass or ceramic container for mixing the solution
B. Wooden utensil for stirring the ingredients
C. Wood or plastic spatula
D. Clean dry towels for blotting the area after treatment
E. Stiff bristle brushes (non-metallic)
F. Garden hose and nozzle
G. Masking tape
PART 3---EXECUTION
3.01 EXAMINATION
A. Examine the masonry surface CAREFULLY to determine the
cause of staining before proceeding with any cleaning
operation.
3.02 PROTECTION
A. Surface Preparation:
1. Before attempting the stain removal, clean attached
or nearby metal items and coat them with a quick
drying, clear coating such as varnish, shellac or a
plastic spray-on/brush-on coating.
2. If possible, remove the sources of moisture to
prevent further oxidation of the metal.
Where the source of the stain is an embedded
anchor, tie, or other device, the only remedy is to
eliminate the moisture at its source as coating
would be impossible.
3.03 ERECTION, INSTALLATION, APPLICATION
A. Thoroughly rinse the area to be treated with mineral
water to prevent too deep a penetration of the chemical
cleaning agent.
B. For Light Stains:
1. Brush or spray on a solution of oxalic acid based
on 1 part acid powder to 10 parts water by weight.
-OR-
Mix chemicals with clay or acid-free paper pulp to
form a thick paste.
2. Follow poulticing instructions in Section 3.03 E.-L. below.
C. For Normal Treatment:
1. Mix 7 part glycerine, 1 part sodium citrate and 6
parts warm water.
2. Thoroughly moisten the stained surface with this
liquid. Be sure to dampen well beyond the stain.
3. 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).
4. Follow poulticing instructions in Section 3.03 E.-L. below.
D. For Stubborn Stains:
1. Wet the affected area with a solution of 1 part
sodium citrate and 6 parts water.
2. Mix sodium hydrosulfite or sodium hypochlorite with
filler material such as attapulgite clay to form a
thick paste.
NOTE: THIS TREATMENT MAY CAUSE SOME ETCHING OF
POLISHED SURFACES BUT CAN BE CORRECTED BY
REPOLISHING - SEE 04455-02-P "REPOLISHING MARBLE".
-OR-
3. Prepare a commercial rust remover poultice
following manufacturer's instructions.
4. Follow poulticing instructions in Section 3.03 E.-L. below.
E. Using a wooden or plastic spatula, apply the poultice to
the stained area 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
masking tape in order to prevent too quick of an
evaporation.
H. Re-wet the poultice with clean water as needed and leave
to dry (approximately 48 hours).
1. FOR SODIUM HYDROSULFITE POULTICE, LEAVE IN PLACE
ONLY FOR 30 MINUTES PER APPLICATION.
2. FOR COMMERCIAL RUST REMOVER POULTICE, LEAVE IN
PLACE ONLY FOR 24 HOURS.
I. Remove the poultice with a wooden or plastic spatula to
avoid scratching the surface.
J. FOR SODIUM HYDORSULFITE POULTICE, FLUSH SURFACE
IMMEDIATELY WITH SODIUM CITRATE.
K. Rinse the cleaned area with mineral water, blot with
clean towels and allow the surface to dry.
L. Once the surface has dried completely, check for
remaining residue and repeat the treatment if necessary.
END OF SECTION
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