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Historic Preservation - Technical Procedures

Spectitle:

Poulticing Rust Stains From Limestone And Marble

Procedure code:

0440006R

Source:

Outdoor Sculpture Manual - Center For Public Buildings

Division:

Masonry

Section:

Stonework

Last Modified:

07/02/2012

Details:

Poulticing Rust Stains From Limestone And Marble



POULTICING RUST STAINS FROM LIMESTONE AND MARBLE


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 removing rust stains
         from limestone and marble by poulticing using different
         chemical solvents or by using a paste containing a
         commercial rust remover.  

         NOTE:  THIS PROCEDURE MAY ALSO BE USED FOR REMOVING RUST
         STAINS FROM BRICK MASONRY.

    B.  Metallic stains from iron or steel have the appearance of
         rust.  This type of staining is often caused by the run-off
         from flashing, gutters, statuary and fasteners. The source of the rusty runoff should be          determined and cause abated.  Cleaning should be undertaken after rectifying deficiencies          causing the rusting.  Following cleaning, the surfaces should be inspected after several          episodes of precipitation to confirm success of repairs or other treatments.

    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).

    D.   For additional information on poulticing, see 04455-02-R.

    E.   For general information on the characteristics, uses and
         problems associated with limestone, see 04460-01-S; for
         marble, see 04455-01-S.


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.  ProSoCo, Inc.
         www.prosoco.com
         
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 Normal Treatment:

         1.   Sodium Citrate (appears like enlarged salt
              granules):

              a.   Other chemical or common names include Citrate
                   of soda*.

              b.   Available from chemical supply house, rug
                   store or pharmaceutical supply distributor.

         2.   Glycerine:

              a.   Other chemical or common names include
                   Glycerol; Glyceryl hydroxide; Glycyl alcohol;
                   1,2,3-propanetriol; Propenyl alcohol.

              b.   Potential hazards:  FLAMMABLE.

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

    B.   For Light Stains:

         1.   Oxalic acid (COOH)2 or (H2C2O4):

              a.   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.

              b.   Other chemical or common names include
                   Ethanedioic acid.

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

              d.   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.)

    C.   For Stubborn Stains:

         1.   Sodium Hydrosulfite (NaHSO4):

              a.   Other chemical or common names include Sodium
                   Hyposulfite; Sodium Subsulfite; Sodium
                   Thiosulfate; Antichlor*; Hypo*; Hyposulfite of
                   soda*.

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

              c.   Available from chemical supply house, dry
                   cleaning supply distributor, drugstore or
                   pharmaceutical supply distributor,
                   photographic supply distributor (not camera
                   shop), stone dealer, or water and sanitation
                   supply distributor.

              -OR-

              Sodium Hypochlorite:

              a.   Other chemical or common names include
                   Bleaching solution*; Household bleach*;
                   Laundry bleach*; Solution of chlorinated
                   soda*.

              b.   Potential Hazards:  CORROSIVE TO FLESH.

              c.   Available from chemical supply house, grocery
                   store or supermarket, hardware store or
                   janitorial supply distributor.

              NOTE:  A POULTICE USING EITHER OF THESE CHEMICALS
              SHOULD ONLY BE LEFT ON THE SURFACE FOR 30 MINUTES
              PER APPLICATION AND AFTER THE REMOVAL, THE SURFACE
              SHOULD BE IMMEDIATELY FLUSHED WITH A SODIUM CITRATE
              SOLUTION.  (This treatment may cause some etching
              of polished surfaces but can be corrected by
              repolishing - see 04455-02-P "Repolishing Marble").

              -OR-

              Commercial rust remover, such as "Sure Klean
              Ferrous Stain Remover (ProSoCo, Inc.), or approved
              equal.

              NOTE:  THIS POULTICE APPLICATION SHOULD ONLY SET
              FOR 24 HOUR PERIODS AS OPPOSED TO TYPICAL 48 HOUR
              SET PERIOD.

    C.   White absorbent material (molding plaster, untreated
         white flour, white tissue, paper towels, powdered chalk,
         talc, fullers earth, acid-free paper pulp or laundry
         whiting).

    D.   Plastic sheeting

    E.   Mineral water

2.02 EQUIPMENT

    A.   Glass or ceramic container for mixing the solution

    B.   Wooden utensil for stirring the ingredients

    C.   Wood or plastic spatula

    D.   Clean dry towels for blotting the area after treatment

    E.   Stiff bristle brushes (non-metallic)

    F.   Garden hose and nozzle

    G.   Masking tape


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Examine the masonry surface CAREFULLY to determine the
         cause of staining before proceeding with any cleaning
         operation.

3.02 PROTECTION

    A.   Surface Preparation:

         1.   Before attempting the stain removal, clean attached
              or nearby metal items and coat them with a quick
              drying, clear coating such as varnish, shellac or a
              plastic spray-on/brush-on coating.  

         2.   If possible, remove the sources of moisture to
              prevent further oxidation of the metal.
              Where the source of the stain is an embedded
              anchor, tie, or other device, the only remedy is to
              eliminate the moisture at its source as coating
              would be impossible.

3.03 ERECTION, INSTALLATION, APPLICATION

    A.   Thoroughly rinse the area to be treated with mineral
         water to prevent too deep a penetration of the chemical
         cleaning agent.

    B.   For Light Stains:  

         1.   Brush or spray on a solution of oxalic acid based
              on 1 part acid powder to 10 parts water by weight.

              -OR-

              Mix chemicals with clay or acid-free paper pulp to
              form a thick paste.  

         2.   Follow poulticing instructions in Section 3.03 E.-L. below.

    C.   For Normal Treatment:

         1.   Mix 7 part glycerine, 1 part sodium citrate and 6
              parts warm water.

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

         3.   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).

         4.   Follow poulticing instructions in Section 3.03 E.-L. below.

    D.   For Stubborn Stains:

         1.   Wet the affected area with a solution of 1 part
              sodium citrate and 6 parts water.

         2.   Mix sodium hydrosulfite or sodium hypochlorite with
              filler material such as attapulgite clay to form a
              thick paste.

              NOTE:  THIS TREATMENT MAY CAUSE SOME ETCHING OF
              POLISHED SURFACES BUT CAN BE CORRECTED BY
              REPOLISHING - SEE 04455-02-P "REPOLISHING MARBLE".

         -OR-

         3.   Prepare a commercial rust remover poultice
              following manufacturer's instructions.

         4.   Follow poulticing instructions in Section 3.03 E.-L. below.

    E.   Using a wooden or plastic spatula, apply the poultice to
         the stained area 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 in order to prevent too quick of an
         evaporation.

    H.   Re-wet the poultice with clean water as needed and leave
         to dry (approximately 48 hours).

         1.   FOR SODIUM HYDROSULFITE POULTICE, LEAVE IN PLACE
              ONLY FOR 30 MINUTES PER APPLICATION.

         2.   FOR COMMERCIAL RUST REMOVER POULTICE, LEAVE IN
              PLACE ONLY FOR 24 HOURS.

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

    J.   FOR SODIUM HYDORSULFITE POULTICE, FLUSH SURFACE
         IMMEDIATELY WITH SODIUM CITRATE.

    K.   Rinse the cleaned area with mineral water, blot with
         clean towels and allow the surface to dry.

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

                         END OF SECTION
 


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