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Historic Preservation - Technical Procedures

Spectitle:
Removing Paint From Bronze

Procedure code:
0501019R

Source:
National Capitol Region Specifications

Division:
Metals

Section:
Metal Materials

Last Modified:
02/24/2012

Details:
Removing Paint From Bronze



REMOVING PAINT FROM BRONZE


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing paint from
         bronze features and refinishing using an oxidizing agent
         and oil.

    B.   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).

    C.   Cleaning and refinishing bronze is highly specialized and
         should be conducted under the supervision of a metals
         conservator.  All chemicals and their application should
         be approved prior to use by the metals conservator to
         ensure protection of historic metals.  

PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   Leo Silfen, Inc.
         Industrial Chemical Division
         525 Fourth Avenue
         Mt. Vernon, New York
         914/699-4800

    B.   McIntyre Metal Maintenance
         1615 South Broadway
         Los Angeles, California

    C.   Enthone Corporation
         New Haven, CT

    D.   Stanley Chemical
         401 Berlin Street
         East Berlin, CT 06023

2.01 MATERIALS

    A.   Metal Cleaner:  Suitable cleaners are:

         1.   Marine Type Metal Polish Formula 90 (Industrial
              Chemical Division, Leo Silfen, Inc.), or approved
              equal.

         2.   McIntyre Metal Cleaner (McIntyre Metal
              Maintenance), or approved equal.

    B.   Standard Solvent:

         1.   A mixture of 75% toluene, 24% acetone, and 1% butyl
              acetate.  (Available from chemical supply firms.)

         2.   As an alternate, solvents normally used for
              thinning nitro-cellulose lacquers, such as "DuPont
              Lacquer Solvent No. 3661-S" (for use in mid-
              temperature, 50  to 80 F).

    C.   Inhibitor/Cleaner:  1% Benzotriazole solution in warm
         water (40 grams Benzotriazole/gallon of water).

    D.   Paint/Lacquer Remover:  Methylene chloride flush-away
         type remover, such as "S-26", (Enthone Corporation), or
         approved equal.

    E.   Mild Soap:  Ivory or a mild detergent with pH of
         approximately 8.0.

    F.   Clear Coating:  Acrylic lacquer containing acrylic ester
         resins dissolved in toluene with benzotriazole as
         corrosion inhibitor, such as "Incralac", (Stanley
         Chemical), or approved equal.

    G.   Abrasive:  Silicon carbide abrasive pads, such as
         "Scotch-Brite", (3M Company), or standard commercially
         available pumice stone; or stainless steel wool.  DO NOT
         USE STEEL WOOL, WHICH MAY PROMOTE DISCOLORATION OF THE
         BRONZE.

    H.   Oxidizing Agent:  Aluminum chloride or liquid sulfur.

    I.   Cloth:  Clean cotton waste.


PART 3---EXECUTION

3.01 PREPARATION

    A.   Protection: Protect all masonry surfaces immediately
         adjacent to or below the area to be cleaned by covering
         with polyethylene sheeting.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   Remove old paint using paint remover applied with a
         cotton cloth wiped along the grain of the metal.

    B.   Allow the remover to stand on the paint for several
         minutes, then remove by wiping with a cotton cloth or by
         flushing with water.  Several applications of the
         stripper may be necessary in order to remove all traces
         of the paint from the metal.

    C.   Follow the stripping operation with an application of
         metal cleaner on a soft cloth, rubbing along the grain of
         the metal.  Clean surface dirt and grease only; do not
         rub down to bright metal.  Rinse thoroughly with clear
         water.

    D.   Persistent stains or badly corroded areas may be cleaned
         using an abrasive and standard solvent under the
         direction of a metals conservator.  All cleaner residue
         should be removed by washing the metal surface at least
         twice with a standard solvent.

    E.   See 05010-08-P for guidance on lacquering bronze.

    F.   See 05010-22-R for guidance on cleaning and oiling
         statuary bronze features.

                         END OF SECTION