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Historic Preservation - Technical Procedures

Spectitle:
Removing Bitumen From Granite

Procedure code:
0446514R

Source:
National Captiol Region Specifications

Division:
Masonry

Section:
Granite

Last Modified:
02/24/2012

Details:
Removing Bitumen From Granite



REMOVING BITUMEN FROM GRANITE


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

1.01 SUMMARY

    A.   This procedure includes guidance on cleaning and removing
         localized bitumen residue from granite surfaces using a
         combination of methods, including dry ice, poulticing or
         abrasive cleaning.  For guidance on the general cleaning
         of surface dirt on granite, see 04465-08-R.

    B.   A poultice is usually made by adding a solvent or
         chemical cleaning agent to water and blended with an
         inert filler to make a smooth paste.  

         1.   The paste is applied over the stain using a trowel
              or spatula.

         2.   The liquid portion of the paste migrates into the
              stone where it dissolves some of the staining
              material.  

         3.   Then the liquid gradually moves back beyond the
              stone surface and into the poultice, from which it
              evaporates, leaving its burden of dissolved
              staining material in the poultice.

         4.   When the poultice has dried, it is scraped and
              brushed away.

    C.   Wet abrasive cleaning of stone masonry involves using a
         combination of air, water and abrasive applied to the
         stone surface using a "wet-head" gun with single or
         multiple jets.  

         1.   Wet abrasive methods are preferred over dry
              abrasive methods because they tend to be less harsh
              on the stone surface.  HOWEVER, ABRASIVE CLEANING
              SHOULD ALWAYS BE UNDERTAKEN USING CAUTION, AS IT
              CAN BE HARMFUL TO BOTH THE STONE AND THE OPERATOR
              IF THE OPERATING TECHNIQUES ARE NOT CAREFULLY
              EVALUATED PRIOR TO COMMENCING WORK.  

         2.   Factors that should be considered include air/water
              pressure, nozzle size and type, type of abrasive,
              amount of abrasive, skill of the operator, and
              supervision of the work.

         3.   For guidance regarding the dangers of using
              abrasive cleaning on historic buildings, see 04510-
              05-S.  For guidelines on using high-pressure
              cleaning equipment on masonry, see 04510-04-S.

    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.   For Polished Granite:

         1.   Carbon dioxide or dry ice

         2.   Solvent such as any of the following:

              Naphtha

              -OR-

              Mineral Spirits:

              a.   Petroleum distillate that is used especially
                   as a paint or varnish thinner.

              b.   Other chemical or common names include Benzine*(not Benzene); Naphtha*;
Petroleum spirits*;
                   Solvent naphtha*.

              c.   Potential Hazards:  TOXIC AND FLAMMABLE.

              d.   Safety Precautions:

                   1)   AVOID REPEATED OR PROLONGED SKIN CONTACT.

                   2)   ALWAYS wear rubber gloves when handling
                        mineral spirits.

                   3)   If any chemical is splashed onto the
                        skin, wash immediately with soap and
                        water.

              e.   Available from construction specialties
                   distributor, hardware store, paint store, or
                   printer's supply distributor.

              -OR-

              Methylene Chloride:

              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.

              a.   Other chemical or common names include
                   Dichloromethane; Methylene bichloride;
                   Methylene dichloride.

              b.   Potential Hazards:  TOXIC.

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

              -OR-

              Perchloroethylene

              -OR-

              Ethyl Alcohol (C2H5OH):

              a.   Other chemical or common names include
                   Ethanol; Ethyl hydroxide; Ethylic alcohol;
                   Methyl carbinol; Cologne spirits*; Fermentation
                   alcohol*; Grain alcohol*; proof spirit*;
                   Rectified spirit*; Spirits of wine*.

              b.   Potential Hazards:  FLAMMABLE.

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

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

              -OR-

              Acetone (C3H6O):

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

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

              c.   Potential Hazards:  VOLATILE AND FLAMMABLE
                   SOLVENT

              d.   Available from chemical supply house or
                   hardware store.

              -OR-

              Ethyl Acetate

              -OR-

              Amyl Acetate:

              a.   Other chemical or common names include Amyl
                   acetic ester; 1-pentanol acetate; Banana oil*;
                   Pear oil*.

              b.   Potential Hazards:  FLAMMABLE.

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

              -OR-

              Toluene(C7H8):

              a.   A liquid, aromatic hydrocarbon that resembles
                   benzene but is less volatile, flammable and
                   toxic; Is produced commercially from light
                   oils from coke-oven gas and coal tar and from
                   petroleum, and is used as a solvent, in
                   organic synthesis and an antiknock agent for
                   gasoline.

              b.   Other chemical or common names include Toluol.

              c.   Potential Hazards:  TOXIC AND FLAMMABLE.

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

              -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.

              -OR-

              Trichlorethylene:

              CAUTION:  TRICHLOROETHYLENE IS HIGHLY TOXIC AND MAY
              REACT WITH STRONG ALKALIS SUCH AS FRESH CONCRETE TO
              FORM DANGEROUS GASES.

              a.   Other chemical or common names include Ethinyl
                   trichloride.

              b.   Potential Hazards:  TOXIC.

              c.   Available from automotive supply distributor,
                   chemical supply house (both commercial and
                   scientific), dry cleaning supply distributor,
                   paint store, photographic supply distributor
                   (not camera shop), or printer's supply
                   distributor.

         3.   White absorbent material (molding plaster,
              untreated white flour, white tissue, paper towels,
              powdered chalk, talc, fullers earth or laundry
              whiting).

         4.   Mineral water

         5.   Plastic sheeting

         6.   Clean dry towels for blotting the area after
              treatment

    B.   For Rough-Surfaced Granite:

         1.   Clean, potable water

         2.   Dry-grit and wet-grit blast, Black Beauty Slag No.
              8-10.

         3.   Plastic sheeting

         4.   Clean dry towels for blotting the area after
              treatment

2.02 EQUIPMENT

    A.   For Polished Granite:

         1.   Soft fiber-bristle brushes

         2.   Wood or plastic spatula

         3.   Glass or ceramic container for mixing the solution

         4.   Wooden utensil for stirring the ingredients

         5.   Masking tape

         6.   Putty knife

         7.   Hammer

    B.   For Rough-Surfaced Granite:

         1.   Soft fiber-bristle brushes

         2.   Wood or plastic spatula

         3.   Pressure water rinsing equipment (measuring between
              100 and 400 psi for low-pressure; between 400 and
              800 psi for medium pressure).

         4.   Fan-type spray tips (15 degree fan spray)


PART 3---EXECUTION

3.01 ERECTION, INSTALLATION, APPLICATION

    NOTE:  BEGIN CLEANING BY USING THE GENTLEST METHOD POSSIBLE.
    TEST CLEAN A SMALL AREA BEFORE ATTEMPTING TO CLEAN LARGE AREAS
    TO DETERMINE APPROPRIATE DWELL TIMES AND NUMBER OF
    APPLICATIONS NECESSARY TO ADEQUATELY REMOVE THE STAIN.

    A.   For Polished Granite:  

         1.   Scrape off bulk of residue without damaging stone
              surface, using a wood or plastic spatula.

         2.   Spray the bitumen with carbon dioxide or apply dry
              ice to make the material brittle.  CAUTION: DO NOT
              USE THIS PROCEDURE ON WET MASONRY.

         3.   Loosen the bitumen by tapping it with a small
              hammer.

         4.   Using a putty knife, pry the bitumen from the
              granite surface.

         5.   Remove any remaining residue by applying a poultice
              containing a solvent, tested for its suitability on
              granite.  

              a.   Thoroughly rinse the area to be treated with
                   mineral water.

              b.   Mix the liquid solution to be used in a glass
                   or ceramic bowl.

              c.   Thoroughly moisten the stained surface with
                   this liquid.  Be sure to dampen well beyond
                   the stain.

              d.   Mix the remaining liquid with the white
                   absorbent material to form a paste the
                   consistency of oatmeal or cake icing.
                   (Approximately one pound of paste is needed
                   for every square foot of surface area to be
                   treated).

              e.   Using a wooden or plastic spatula, apply the
                   paste to the stained surface in layers no more
                   than 1/4 inch thick.  The poultice should
                   extend well beyond the stain to prevent
                   forcing the stain into previously clean stone.

              f.   Check the coating for air pockets or voids.

              g.   Cover the poultice with plastic sheeting and
                   seal with masking tape.

              e.   Let set for 48 hours (unless otherwise
                   specified).

              f.   After set period, dampen the poultice with
                   mineral water.

              g.   Remove the poultice with a wooden or plastic
                   spatula to avoid scratching the surface.

              h.   Again, thoroughly rinse the cleaned area with
                   mineral water, blot with clean towels and
                   allow the surface to dry.

              i.   Once the surface has dried completely, check
                   for remaining residue and repeat the treatment
                   if necessary.

    B.   For Rough-Surfaced Granite:

         1.   Scrape off bulk of residue without damaging stone
              surface, using a wood or plastic spatula.

         2.   Rinse granite surface using pressure-rinsing
              equipment.  Maximum 1,000 PSI, 5-10 GPM, 25  fan
              angle, not less than 6" from surface, at an angle
              of 45  to 90  from wall surface.

         3.   Wet-grit blast at 400 PSI.  Provide sand-bag dams
              to collect run-off grit and dirt.

         4.   Remove remaining residue by applying a poultice
              containing a solvent, tested for its suitability on
              granite.  See 3.01 A.5.a. through A.5.i. above for
              guidance.

         NOTE: ABRASIVE CLEANING TO REMOVE BITUMEN MAY BE
         ACCEPTABLE FOR USE ON ROUGH-SURFACED GRANITE ONLY - NEVER
         ON POLISHED GRANITE.  APPROVAL FROM THE RHPO IS
         RECOMMENDED BEFORE USING ABRASIVE CLEANING TECHNIQUES ON
         MASONRY MATERIALS.

                         END OF SECTION