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