Historic Preservation - Technical Procedures
Poulticing Bronze And Copper Stains From Concrete
Hstrc Concrete: Investigation & Rpr/Pre-Conf Training - 1989
Poulticing Bronze And Copper Stains From Concrete
POULTICING BRONZE AND COPPER STAINS FROM CONCRETE
THE CLEANING OR REMOVAL OF STAINS FROM CONCRETE MAY INVOLVE THE
USE OF LIQUIDS, DETERGENTS OR SOLVENTS WHICH MAY RUN OFF ON
ADJACENT MATERIAL, DISCOLOR THE CONCRETE OR DRIVE THE STAINS DEEPER
INTO POROUS CONCRETE. USE THE PRODUCTS AND TECHNIQUES DESCRIBED
HERE ONLY FOR THE COMBINATIONS OF DIRT/STAIN AND CONCRETE SPECIFIED.
A. This procedure includes guidance on removing bronze and
copper stains from concrete by poulticing with a mixture
of aluminum chloride or ammonium chloride, ammonium
hydroxide and water.
B. Green stains on concrete, and sometimes brown stains, are
common where water has flowed over copper or bronze.
C. Safety Precautions:
1. DO NOT save unused portions of stain-removal
2. DO NOT store any chemicals in unmarked containers.
3. EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY
SOLVENT IS USED. USE RESPIRATORS WITH SOLVENT
4. No use of organic solvents indoors should be
allowed without substantial air movement. Use only
spark-proof fans near operations involving
5. Provide adequate clothing and protective gear where
the chemicals are indicated to be dangerous.
6. Have available antidote and accident treatment
chemicals where noted.
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).
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. Aluminum Chloride: Available from chemical supply house,
drugstore or pharmaceutical supply distributor.
Ammonium Chloride - salt-like substance (NH4Cl):
1. A white crystalline volatile salt that is used in
dry cells and as an expectorant.
2. Other chemical or common names include Ammonium
hydrochloride; Chloride of Ammonia*; Hydrochloride
of Ammonia*; Muriate of Ammonia*; Sal Ammoniac*.
3. Potential hazards: TOXIC; CORROSIVE TO FLESH;
CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS.
4. Available from chemical supply house, dry cleaning
supply distributor, drugstore or pharmaceutical
supply distributor, or hardware store.
B. Ammonium Hydroxide:
1. Other chemical or common names include Ammonia
water*; Aqua ammonia*; Household ammonia*.
2. Potential hazards: TOXIC; MAY IRRITATE THE EYES.
3. Available from chemical supply house, grocery store
or pharmaceutical supply distributor, or hardware
C. Filler material such as diatomaceous earth or talc
D. Mineral water
E. Plastic sheeting
F. Clean dry towels for blotting the area after treatment
G. Masking tape
H. Scouring Powder
I. Clean, potable water
J. Accessible source of water, soap and towels for washing
and rinsing in case of emergencies associated with the
use of chemicals
A. Glass or ceramic container for mixing the solution
B. Wooden utensil for stirring the ingredients
C. Wood or plastic spatula
D. Stiff bristle brush (non-metallic)
1. Provide adequate wash solutions (i.e. water, soap
and towels) before starting the job.
2. Whenever acid is used, the surface should be
thoroughly rinsed with water as soon as its action
has been adequate. Otherwise it will continue
etching the concrete even though the stain is gone.
3.02 ERECTION, INSTALLATION, APPLICATION
NOTE: DO NOT TRY MORE THAN ONE TREATMENT ON A GIVEN AREA
UNLESS THE CHEMICALS USED FROM PRIOR TREATMENT HAVE BEEN
A. Dry mix by weight 1 part ammonium chloride or aluminum
chloride with 4 parts fine-powdered inert material such
as diatomaceous earth or talc.
B. Combine the dry mix with (1 part concentrated ammonium
hydroxide diluted with 2 to 9 parts of water) to form a
smooth paste. If the concentrated solution is not
available, use household ammonia without diluting.
C. Thoroughly wet the concrete surface to be treated with
clean, clear water.
D. Apply the mixture to the stained area using a wood or
plastic spatula (approximately 1/8 to 1/4 inch thick) and
allow to dry. Be sure to spread the poultice well beyond
the stained area. The liquid portion of the paste will
migrates into the concrete where it will dissolve some of
the staining material. Then the liquid will gradually
move back beyond the concrete surface and into the
poultice, where it will evaporate, leaving the dissolved
staining material in the poultice.
E. When the poultice has dried, brush or scrape it off with
a wooden scraper.
F. Using a stiff bristle brush, scrub the surface with
scouring powder and clean water to remove any residual
G. Thoroughly rinse the area with clean, clear water and
allow to dry.
H. Repeat the process as necessary to sufficiently remove
END OF SECTION