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Removing Painted Graffiti From Sandstone
REMOVING PAINTED GRAFFITI FROM SANDSTONE
THE CLEANING OR REMOVAL OF STAINS FROM STONE MAY INVOLVE THE USE
OF LIQUIDS, DETERGENTS OR SOLVENTS WHICH MAY RUN OFF ON ADJACENT
MATERIAL, DISCOLOR THE STONE OR DRIVE THE STAINS DEEPER INTO
POROUS STONES. USE THE PRODUCTS AND TECHNIQUES DESCRIBED HERE
ONLY FOR THE COMBINATIONS OF DIRT/STAIN AND STONE SPECIFIED.
PART 1---GENERAL
A. This procedure includes guidance on the removal of
paint-based graffiti from sandstone using a chemical
paint stripper or poultice. For additional information
and/or alternative methods of removing graffiti from
sandstone, see 04200-01-S.
B. Latex paints tend to remain primarily on the surface of
stone materials as opposed to oil based paints, which
tend to penetrate into the stone and remain there.
C. Historic Structures Precautions:
1. Do not use acids or flame tools to strip paint
from stone, as it will damage the surface.
2. Do not use steel or metal spatulas or tools to
scrape stone because of the likelihood of
scratching, chipping, gouging, or otherwise
marring the surface.
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).
E. For general information on the characteristics, uses
and problems associated with sandstone, see 04470-01-S.
PART 2---PRODUCTS
2.01 MANUFACTURERS
A. ProSoCo, Inc.
www.prosoco.com
2.02 MATERIALS
A. 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.), or
approved equal.
NOTE: AVOID COMMERCIAL STRIPPERS WHICH CONTAIN WAX,
CHOOSING INSTEAD THE "WASHABLE IN WATER" TYPES.
B. Clean, potable water
C. Clean, natural fiber rags for drying
D. Solvents such as acetone or denatured alcohol:
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.
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 should be a satisfactory
substitute for ethyl alcohol for stain removing
purposes.
E. 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).
2.03 EQUIPMENT
A. Garden hose and nozzle
B. Wood or plastic spatulas
C. Stiff fiber or jute bristle brushes (No Metallic)
PART 3---EXECUTION
3.01 EXAMINATION
A. Examine the sandstone surface CAREFULLY to determine
the cause of staining before proceeding with any
cleaning operation.
B. Identify the substance used to create the graffiti.
C. 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
NOTE: SANDBLASTING OR OTHER ABRASIVE TECHNIQUES TO REMOVE
PAINT SHOULD BE AVOIDED. INSTEAD SMALL TEST PATCHES SHOULD
BE TRIED USING SUCH SOLVENTS AS ACETONE, DENATURED ALCOHOL,
AND COMMERCIAL PAINT STRIPPERS.
A. Thoroughly rinse the stained area with clean, clear
water, while carefully removing loose paint using a
wooden scraper. Allow surface to thoroughly dry.
B. Brush apply a coat of commercial paint stripper over
the surface (approximately 1/8" thick), and allow to
dwell until paint is lifted from the surface; follow
manufacturer's instructions.
-OR-
Brush apply a solvent such as acetone or detatured
alcohol.
C. Scrape off softened paint with a wooden spatula.
D. Thoroughly rinse the surface with clean, clear water
and allow to dry.
E. Repeat the process as necessary to sufficiently remove
the stain.
F. For stubborn paint stains, poulticing may be required.
1. Create a poultice by mixing an appropriate solvent
with a filler material.
2. 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 masonry where
it will dissolve some of the staining material.
Then the liquid will gradually move back beyond
the masonry surface and into the poultice, where
it will evaporate, leaving the dissolved staining
material in the poultice.
3. Allow poultice to dwell, keeping it moist until
the stain has lifted. Secure a polyethylene sheet
over the poultice to reduce evaporation. Exact
length of dwell time will vary and will require
periodic inspection of the substrate.
4. 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.
5. The poultice should fall off naturally as it
dries. Remove remaining material with a wooden
spatula and natural bristle brush.
6. Rinse the surface thoroughly with clean, clear
water and allow to dry.
7. Repeated applications of poultice may be required.
3.03 ADJUSTING/CLEANING
A. Upon completion of the masonry cleaning work, clean
window glass and spattered adjacent surfaces.
END OF SECTION
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