U.S. General Services Administration
Technical Procedures Disclaimer
Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
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We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
TAKE SPECIAL CARE TO PROTECT ADJACENT MATERIALS FROM DAMAGE BY SPLASHING OR RUN OFF THAT MAY CONTAIN CLEANING OR STRIPPING PRODUCTS AS WELL AS PAINT, COAINGS AND SOILING REMOVED FROM TREATED SURFACES. DO NOT USE THIS PROCEDURE ON METALS OTHER THAN THOSE SPECIFIED. REVIEW MANUFACTURER’S CAUTIONS AND APPLICABLE FEDERAL, STATE AND LOCAL REGULATIONS GOVERNING PRODUCT USE AND CONTROL OF HAZARDOUS MATERIALS BEFORE UNDERTAKING WORK INVOLVING REMOVAL OF PAINTS AND COATINGS; ADJUST PRODUCT SELECTION AND METHODS ACCORDINGLY. TEST MILDEST, MOST ENVIRONMENTALLY BENIGN FORMULATIONS FIRST BEFORE PROCEDING TO STRONGER CHEMICALS AND HARSHER METHODS.
PART 1–GENERAL
1.01 SUMMARY
- This procedure includes guidance on removing paint from bronze features and refinishing using an oxidizing agent and oil.
- See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Submittals
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- 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).
- 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
- Leo Silfen, Inc. Industrial Chemical Division 136 Long Ridge Road Bedford, New York 914/234-9303
- Dumond Chemicals www.dumondchemicals.com
- Enthone Corporation New Haven, CT enthone.com
- Stanley Chemical East Berlin, CT 06023 www.stanchem-inc.com
- Dumond Chemicals www.dumondchemicals.com
2.01 MATERIALS
- Metal Cleaner: Suitable cleaners are:
- Marine Type Metal Polish Formula 90 (Industrial Chemical Division, Leo Silfen, Inc.), or approved equal.
- Standard Solvent:
- A mixture of 75% toluene, 24% acetone, and 1% butyl acetate. (Available from chemical supply firms.)
- 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).
- Inhibitor/Cleaner: 1% Benzotriazole solution in warm water (40 grams Benzotriazole/gallon of water).
- Paint/Lacquer Remover: Methylene chloride flush-awaytype remover, such as “S-26”, (Enthone Corporation), or approved equal. SAFER SUBSTITUTES include SmartStrip, SmartStripPro and Peel Away 1 (Dumond Co.), and “Aircraft Non-Methylene Chloride Paint Remover” (Klean-Strip.com)
- Mild Soap: Ivory or a mild detergent with pH of approximately 8.0.
- Clear Coating: Acrylic lacquer containing acrylic ester resins dissolved in toluene with benzotriazole as corrosion inhibitor, such as “Incralac”, (Stanley Chemical), or approved equal.
- 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.
- Oxidizing Agent: Aluminum chloride or liquid sulfur.
- Cloth: Clean cotton waste.
PART 3–EXECUTION
3.01 PREPARATION
- 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
- Remove old paint using paint remover applied with a cotton cloth wiped along the grain of the metal.
- 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.
- 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.
- 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.
- See 05010-08-P for guidance on lacquering bronze.
- See 05010-22-R for guidance on cleaning and oiling statuary bronze features.