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Historic Preservation - Technical Procedures

Spectitle:
Removing Paint-Based Graffiti From Concrete

Procedure code:
0371021R

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

Division:
Concrete

Section:
Concrete Cleaning

Last Modified:
02/24/2012

Details:
Removing Paint-Based Graffiti From Concrete



REMOVING PAINT-BASED GRAFFITI 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-based
         graffiti from concrete by scrubbing with proprietary
         cleaners or chemical solvents.  For guidance on removing
         ink-based graffiti or stains, see 03710-24-R.

    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.

         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 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.   Denatured Alcohol:

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

         2.   Potential hazards:  TOXIC AND FLAMMABLE.

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

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

    B.   Dichloromethane:  This is one of the best nonproprietary
         cleaners because it can be washed off with water.

         NOTE:  METHYLENE CHLORIDE IS BANNED IN SOME STATES.
         REGULATORY INFORMATION AS WELL AS ALTERNATIVE OR
         EQUIVALENT CHEMICALS MAY BE REQUESTED FROM THE
         ENVIRONMENTAL PROTECTION AGENCY (EPA) REGIONAL OFFICE
         AND/OR THE STATE OFFICE OF ENVIRONMENTAL QUALITY.

         1.   Other chemical or common names include Methylene
              bichloride; Methylene chloride; Methylene
              dichloride.

         2.   Potential Hazards:  TOXIC.

         3.   Available from chemical supply house, dry cleaning
              supply distributor, paint store, photographic
              supply distributor (not camera shop), or printer's
              supply distributor.

    C.   Oxalic Acid (COOH)2 or (H2C2O4):

         1.   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.

         2.   Other chemical or common names include Ethanedioic
              acid.

         3.   Potential Hazards:  TOXIC; CORROSIVE TO CONCRETE,
              STEEL, WOOD OR GLASS.

         4.   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.)

    D.   Hydrogen Peroxide (H202):

         1.   An unstable compound used especially as an
              oxidizing and bleaching agent, an antiseptic, and a
              propellant.

         2.   Other chemical or common names include Peroxide of
              hydrogen*; Solution of hydrogen dioxide*;
              Superoxol*; (hydrogen peroxide is commonly sold as
              a 3% solution; Superoxol is a 30% solution;
              Superoxol causes flesh burns; 3% hydrogen peroxide
              does not).

         3.   Potential Hazards:  TOXIC (when concentrated);
              CORROSIVE TO FLESH (gasoline, kerosene and mineral
              spirits are each a mixture of compounds from
              petroleum, all of which fall within a specified
              range of properties); FLAMMABLE (in high
              concentration).

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

    E.   Anti-graffiti coating for concrete

    F.   Clean, potable water

    G.   Accessible source of water, soap and towels for washing
         and rinsing in case of emergencies associated with the
         use of chemicals.

    H.   Alternative Materials for Stain Removal:

         1.   Solvents:

              Methyl Ethyl Ketone:

              a.   Other chemical or common names include 2-butanone; MEK*.

              b.   Potential Hazards:  TOXIC AND FLAMMABLE.

              c.   Available from chemical supply house, hardware
                   store or paint store.

              -OR-

              Methyl Isobutyl Ketone:

              a.   Other chemical or common names include
                   Asymmetric ethyl methyl acetone; 3-methyl-2-pentanone;
                   Secondary butylmethyl ketone; MIBK*.

              b.   Potential Hazards:  TOXIC AND FLAMMABLE.

              c.   Available from chemical supply house, hardware
                   store or paint store.

              -OR-

              Xylene (C8H10):

              a.   Any of three toxic, flammable, oily, isomeric,
                   aromatic hydrocarbons that are di-methyl
                   homologues of benzene and are obtained from
                   wood tar, coal tar, or petroleum distillates;
                   Also a mixture of xylenes and ethyl-benzene
                   used chiefly as a solvent.

              b.   Other chemical or common names include Xylol;
                   P-xylene; 1,4-dimethyl benzene.

              c.   Potential Hazards:  TOXIC AND FLAMMABLE.

              d.   Available from chemical supply house, hardware
                   store, paint store or printer's supply
                   distributor.

         2.   Proprietary cleaners containing combinations of
              materials such as sodium hydroxide or other alkali,
              dichloromethane or other solvent, and detergent.

2.02 EQUIPMENT

    A.   Stiff bristle brushes (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.   Using a stiff bristle brush, scrub dichloromethane into
         the concrete surface.

    B.   Wait about 2 minutes and rinse thoroughly with clean,
         clear water.  Use a scrub brush to work the water into
         the concrete pores.  If any solution gets on the skin,
         rinse off with soap and water immediately.

    C.   Bleach any remaining paint pigment using a concentrated
         solution of oxalic acid or a strong solution of hydrogen
         peroxide.

         1.   Test the bleach on a small area to be sure it does
              not excessively or unevenly lighten the surface.

         2.   If the test is satisfactory, apply the solution
              liberally to the surface.  Work the solution
              vigorously into the concrete pores using a stiff
              bristle brush and allow to sit for 10 to 15
              minutes.

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

         NOTE:  Other nonproprietary solvents may be tested for
         their effectiveness in stain removal (see Section 2.01
         H.1. for alternatives).

    -OR-

    D.   Use a proprietary cleaning agent (see Section 2.01 H.2
         for alternatives).  Follow the manufacturer's
         instructions for application requirements and
         precautions.  Success will be dependent upon the type of
         cleaner selected and the level of experience or skill of
         the operator.

    F.   When the graffiti has been sufficiently removed, apply an
         anti-graffiti coating from which any new graffiti can be
         easily removed.  Use only anti-graffiti coatings which do
         not change the color of the surface.

                         END OF SECTION