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Historic Preservation - Technical Procedures

Spectitle:

Removing Painted Graffiti From Masonry

Procedure code:

0420005R

Source:

Developed For Hspg (Nps - Sero)

Division:

Masonry

Section:

Unit Masonry

Last Modified:

02/24/2012

Details:

Removing Painted Graffiti From Masonry



REMOVING PAINTED GRAFFITI FROM MASONRY


THE CLEANING OR REMOVAL OF STAINS FROM MASONRY MAY INVOLVE THE
USE OF LIQUIDS, DETERGENTS OR SOLVENTS WHICH MAY RUN OFF ON
ADJACENT MATERIAL, DISCOLOR THE MASONRY OR DRIVE THE STAINS DEEPER
INTO POROUS MASONRY.  USE THE PRODUCTS AND TECHNIQUES DESCRIBED
HERE ONLY FOR THE COMBINATIONS OF DIRT/STAIN AND MASONRY SPECIFIED.


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing painted
         graffiti from historic masonry (this includes spray paint
         and paint-based felt-tipped markers).

    B.   Successful removal of graffiti from masonry is dependent
         upon the type and surface texture of the masonry as well
         as the particular substance applied.

    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.   Union Carbide Corporation
         Old Ridgebury Road
         Danbury, CT  06817
         203/794-2000

    B.   Rohm & Haas
         Independence Mall West
         Philadelphia, PA  19105
         215/592-3000

    C.   GAF Corporation
         1361 Alps Road
         Wayne, NJ  07470
         201/628-4127

    D.   ProSoCo Inc.
         1601 Rock Mountain Blvd.
         Stone Mountain, GA  30083
         404/939-9890

         -OR-

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

    E.   Ashland Chemical
         4550 N. East Expressway
         Doraville, GA  30340
         404/448-7010

2.02 MATERIALS

    A.   Non-ionic detergent such as "Zyfo" or "Tergitol" (Union
         Carbide, or Ashland Chemical), "Triton" (Rohm & Haas),
         "Igepal" (GAF Corporation), or approved equal.

    B.   Trisodium Phosphate:

         NOTE:  THIS CHEMICAL IS BANNED IN SOME STATES SUCH AS
         CALIFORNIA.  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.   Strong base-type powdered cleaning material sold
              under brand names.

         2.   Other chemical or common names include Sodium
              Orthophosphate; Tribasic sodium phosphate;
              Trisodium orthophosphate; TSP*; Phosphate of soda*;
              (also sold under brand names such as).

         3.   Potential Hazards:  CORROSIVE TO FLESH.

         4.   Available from chemical supply house, grocery store
              or supermarket or hardware store.

    C.   Paint Stripper to remove multiple layers of paint
         coatings and graffiti from exterior masonry surfaces
         (remains active for up to 24 hours), such as "Sure Klean
         Heavy Duty Paint Stripper" (ProSoCo, Inc.)

    D.   Clean, natural fiber rags for drying

    E.   Solvents such as acetone, lacquer thinner, N-methy-2-pyrrolidone

         Acetone (C3H6O):

         1.   A volatile fragrant flammable liquid ketone used
              chiefly as a solvent and in organic synthesis and
              found abnormally in urine.

         2.   Other chemical or common names include Dimethyl
              ketone; Propanone

         3.   Potential Hazards:  VOLATILE AND FLAMMABLE SOLVENT

         4.   Available from chemical supply house or hardware
              store.

    F.   Filler material such as attapulgite clay, kaolin,
         fuller's earth, talc, chalk, cotton pads, acid-free
         paper.  (Do not use chalk or iron-containing clay with an
         acid solvent as their chemical reaction will cancel the
         effectiveness of the acid).

    G.   Clean, potable water

2.03 EQUIPMENT

    A.   Garden hose and nozzle

    B.   Non-metallic brushes (non-metallic)

    C.   Wood scrapers


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Identify the substance used to create the graffiti.

    B.   Examine the surrounding area for signs of what may have
         been used to create the graffiti (i.e. spray cans or
         other debris).

3.02 ERECTION/INSTALLATION/APPLICATION

    A.   Begin with the least harsh method of removing paint.

         1.   Wash the area with a solution of trisodium
              phosphate (TSP) and water.  Apply with a non-metallic brush.

         2.   When the paint has softened, scrape off as much as
              possible with a wooden scraper.

         3.   Wash the area again using a non-ionic detergent and
              water.

         4.   Thoroughly rinse the surface with clean, clear
              water.

    B.   If a stronger method is necessary:

         1.   Brush on a commercial paint remover (either a
              solvent such as lacquer thinner or acetone, or a
              methylene chloride-based remover may be used) with
              a non-metallic brush.  Follow manufacturers
              instructions for application and dwell time.  

         2.   When the paint has softened, scrape off as much as
              possible with a wooden scraper.

         3.   Wash the area again using a detergent and soapy
              water and rinse thoroughly with clean water.

    C.   For felt tip marks, use a poultice:

         1.   Pre-wet surface using denatured alcohol.

         2.   Saturate a soft cloth with a mixture of acetone,
              lacquer thinner and N-methy-2-pyrrolidone.  Test
              proportions to find the most effective mixture.

         3.   Gently rub the stain with the saturated cloth.

         4.   To remove remaining stain, prepare a poultice using
              the same solvent mixture as used in C.2. above
              mixed with a filler material such as attapulgite
              clay, kalin or fuller's earth (all clays), talc,
              chalk or whiting, shredded acid-free paper, or
              cotton pads.  Mix to form a thick paste.

         5.   Thoroughly wet the masonry surface to be treated
              with clean, clear water.

         6.   Apply the mixture to the stained area in a 1/4" to
              3/4 " thick layer using a wood or plastic spatula
              and allow to dry.  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.

         7.   Keep poultice moist until stain has lifted.  Exact
              length of time will vary and will require periodic
              inspection of the substrate.

         8.   Once it appears that the stain has lifted, allow
              the poultice to dry out.  As the poultice dries,
              the solvent is re-absorbed by the poultice material
              bringing with it the stain.

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

         10.  Using a stiff bristle brush, scrub the surface with
              scouring powder and clean water to remove any
              residual staining.

         11.  Wash all residue using a non-ionic detergent as in
              Section 3.02 A. above.

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

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

3.03 ADJUSTING/CLEANING

    A.   Upon completion of the masonry cleaning work, clean
         window glass and spattered adjacent surfaces.

                         END OF SECTION