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Historic Preservation - Technical Procedures

Spectitle:
Removing Paint, Shellac And Varnishes From Concrete

Procedure code:
0371032R

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

Division:
Concrete

Section:
Concrete Cleaning

Last Modified:
02/24/2012

Details:
Removing Paint, Shellac And Varnishes From Concrete



REMOVING PAINT, SHELLAC AND VARNISHES 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 paint,
         shellac and varnishes from concrete by scrubbing and
         poulticing.

    B.   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.

              NOTE:  SOME OF THE SOLVENTS LISTED ARE KNOWN
              CARCINOGENS AND MAY BE BANNED IN SOME STATES.

         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.

    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).


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   ProSoCo, Inc.
         755 Minnesota Avenue
         P.O. Box 1578
         Kansas City, KS  66117
         913/281-2700

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 Removing Fresh Paint:

         1.   Scouring powder and detergent

    B.   For Removing Cured Paint, Enamel, Lacquer or Oil-based
         Varnish:

         1.   For Formula 1: (see Section 3.02 B.)

              Benzene (C6H6):

              a.   A colorless, volatile, flammable, toxic,
                   liquid, aromatic hydrocarbon used in organic
                   synthesis, as a solvent and as a motor fuel.

              b.   Other chemical or common names include Benzol;
                   Benzole; Phene; Phenyl hydride; Coal naphtha*;
                   Motor benzol*.

              c.   Potential Hazards:  FLAMMABLE.

              d.   Available from automotive supply distributor,
                   chemical supply house, dry cleaning supply
                   distributor, hardware store or paint store.

              e.   Benzene and benzine should not be confused.
                   Benzene is a distinct chemical compound
                   obtained from coal tar.  Benzine is a mixture
                   of aromatic hydrocarbons of similar boiling
                   points derived from petroleum.

              Denatured Alcohol:

              a.   Other chemical or common names include
                   Methylated spirit*.

              b.   Potential hazards:  TOXIC AND FLAMMABLE.

              c.   Available from hardware store, paint store or
                   printer's supply distributor.

              d.   Denatured alcohol, which carries no liquor
                   tax, should be a satisfactory substitute for
                   ethyl alcohol for stain removing purposes.

              Ethylene Dichloride:

              a.   A colorless pungent flammable gaseous or
                   volatile liquid used especially as a local
                   surface anesthetic.

              b.   Other chemical or common names include 1,2-dichlorethane;
                    Ethylene chloride; Glycol dichloride.

              c.   Potential Hazards:  TOXIC AND FLAMMABLE.

              d.   Available from automotive supply distributor,
                   dry cleaning supply distributor, or paint
                   store.

              Methyl Acetone:  

              a.   A mixture of various proportions of acetone
                   (47 to 51%), methyl acetate (27.5 to 31%) and
                   methyl alcohol (20 to 25%).

              b.   Potential Hazards:  FLAMMABLE.

              c.   Available from chemical supply house, paint
                   store, or photographic supply distributor (not
                   camera shop).

         -OR-

         2.   For Formula 2:

              Sodium Hydroxide (NaOH):

              a.   A white brittle solid that is a strong caustic
                   base used especially in making soap, rayon,
                   and paper.

              b.   Other chemical or common names include Caustic
                   soda*; Hydrate of soda*; Hydrated oxide of
                   sodium*; Lye*; Mineral alkali*; Soda lye*;
                   Sodic hydrate*; Sodium hydrate*.

              c.   Potential Hazards:  CORROSIVE TO FLESH AND
                   FLAMMABLE (WHEN IN CONTACT WITH ORGANIC
                   SOLVENTS).

              d.   Available from chemical supply house,
                   drugstore or pharmaceutical supply
                   distributor, hardware store, or paint store.

         -OR-

         3.   Commercial paint remover such as "Sure Klean 509
              Paint Stripper" (ProSoCo, Inc.), or approved equal.

    C.   For Removing Shellac:

         1.   Wood Alcohol:

              a.   Other chemical or common names include
                   Carbinol; Methanol; Methyl alcohol; Methyl
                   hydrate; Methyl hydroxide; Methyllic alcohol;
                   Colonial spirits*; Columnian spirits*; Green
                   wood spirits*; Manhattan spirits*;
                   Pyroligneous spirit*; Pyroxylic spirit*;
                   Standard wood spirits*; Wood naphtha*; Wood
                   spirit*.

              b.   Potential Hazards:  TOXIC AND FLAMMABLE.

              c.   Available from automotive supply distributor,
                   chemical supply house, dry cleaning supply
                   distributor, drugstore or pharmaceutical
                   supply distributor, hardware store, paint
                   store, or photographic supply distributor (not
                   camera shop).

         -OR-

              Denatured alcohol (see 2.02 B.2. above)

         2.   Hydrochloric Acid (30-35%):

              a.   A strong corrosive irritating acid.

              b.   Other chemical or common names include
                   Chlorhydric acid; Hydrogen chloride; Muriatic
                   acid* (generally available in 18 degree and 20
                   degree Baume solutions); Marine acid*; Spirit
                   of salt*; Spirit of sea salt*.

              c.   Potential Hazards:  TOXIC, CORROSIVE TO FLESH;
                   CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS,
                   FLAMMABLE.

              d.   Available from chemical supply house,
                   drugstore or pharmaceutical supply
                   distributor, or hardware store.

         -OR-

              Phosphoric Acid:

              a.   A syrupy or deliquescent tribasic acid used
                   especially in preparing phosphates (as for
                   fertilizers), in rust-proofing metals, and as
                   a flavoring in soft drinks.


              b.   Other chemical or common names include
                   Orthophosphoric acid.

              c.   Potential Hazards:  CORROSIVE TO FLESH;
                   CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS.

              d.   Available from chemical supply house or
                   hardware store.

    D.   For Removing Old or Dried Paint:

         1.   Muriatic acid:  (see Hydrochloric acid 2.02 C.2.
              above)

         2.   Scouring powder and detergent

    E.   Filler material such as diatomaceous earth or talc

    F.   Mineral water

    G.   Clean, potable water

    H.   Clean dry cloths or paper towels for blotting the area
         after treatment

    I.   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.   For Poulticing:

         1.   Glass or ceramic container for mixing the solution

         2.   Wooden utensil for stirring the ingredients

    B.   Wood or plastic spatula

              C.   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.   To Remove Fresh Paint:

         1.   Blot spilled or unwanted fresh paint with clean
              cloths or paper towels.  DO NOT WIPE THE PAINT.
              THIS WILL DRIVE THE PAINT INTO THE SURFACE.

         2.   Scrub the surface immediately with scouring powder
              and clean, clear water to remove as much of the
              stain as possible.

         3.   If staining remains, wait several days and then
              treat like cured paint (below).

    B.   To Remove Cured Paint, Enamel, Lacquer or Oil-Based
         Varnish:

         1.   Remove as much of loose coating as possible by
              brushing with a stiff (non-metallic) bristle brush.

         2.   Formula 1:  Mix 10 parts methyl acetone, 25 parts
              benzene, 18 parts denatured alcohol and 8 parts
              ethylene dichloride.

              -OR-

              Formula 2:  Mix a solution of 2.5 pounds sodium
              hydroxide in 1 gallon of hot water (this can be
              used in a poultice or applied to the surface by
              brush).

              -OR-

              Use a commercial paint remover.

         3.   Thoroughly wet the concrete surface to be treated
              with clean, clear water.

         4.   Apply the mixture to the stained area using a wood
              or plastic spatula and allow to dry (approximately
              20-30 minutes).  Be sure to spread the poultice
              well beyond the stained area.  The liquid portion
              of the paste will migrate 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.

         5.   When the poultice has dried, brush or scrape it off
              with a wooden scraper.  

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

         7.   Repeat the process as necessary to achieve the
              desired level of cleanliness.

    C.   To Remove Shellac:

         1.   Remove as much of loose coating as possible by
              brushing with a stiff (non-metallic) bristle brush.

         2.   Mix wood alcohol or denatured alcohol with
              diatomaceous earth or talc to form a thick paste.

         3.   Follow poulticing procedures in Section 3.02 B.3-7
              above.

         4.   If a residue remains, scrub the area with scouring
              powder, rinse with clean, clear water and allow to
              dry.

         5.   If there is staining below the surface:

              a.   Mix 1 part hydrochloric acid with 9 to 19
                   parts of water.

                   -OR-

                   Mix 1 part phosphoric acid in 9 parts of
                   water.

              b.   Wash the surface with the solution using a
                   stiff (non-metallic) bristle brush.

              c.   Thoroughly rinse the surface with clean, clear
                   water and allow to dry.

    D.   To Remove More Difficult Coatings (such as old, dried
         paint):

         1.   Remove as much of loose coating as possible by
              brushing with a stiff non-metallic bristle brush.

         2.   Mix 1 part concentrated muriatic acid, 4 parts
              water and 1 part detergent.

         3.   Apply mixture to the surface and scrub with a stiff
              (non-metallic) bristle brush.

         4.   Thoroughly rinse the surface with clean, clear
              water and allow to dry.

         5.   Repeat as necessary to achieve the desired level of
              cleanliness.

                         END OF SECTION