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Historic Preservation - Technical Procedures

Spectitle:

Poulticing Bronze And Copper Stains From Concrete

Procedure code:

0371044R

Source:

Hstrc Concrete: Investigation & Rpr/Pre-Conf Training - 1989

Division:

Concrete

Section:

Concrete Cleaning

Last Modified:

02/24/2012

Details:

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.


PART 1---GENERAL

1.01 SUMMARY

    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
              materials.

         2.   DO NOT store any chemicals in unmarked containers.

         3.   EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY
              SOLVENT IS USED.  USE RESPIRATORS WITH SOLVENT
              FILTERS.

         4.   No use of organic solvents indoors should be
              allowed without substantial air movement.  Use only
              spark-proof fans near operations involving
              flammable liquids.

         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

         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).


PART 2---PRODUCTS

2.01 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.   Aluminum Chloride:  Available from chemical supply house,
         drugstore or pharmaceutical supply distributor.

         -OR-

         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
              store.

    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

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.   Stiff bristle brush (non-metallic)


PART 3---EXECUTION

3.01 PREPARATION

    A.   Protection:

         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
    WASHED AWAY.

    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
         staining.

    G.   Thoroughly rinse the area with clean, clear water and
         allow to dry.

    H.   Repeat the process as necessary to sufficiently remove
         the stain.

                         END OF SECTION