Refinishing Bronze Features
- CSI Division:
- Division 5 - Metals
- Metal Materials
- Last Modified:
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.
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.
A. This procedure include guidance on stripping and refinishing bronze features. Two methods are described in Part 3 of this procedure.
B. 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
- 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).
A. Product Data:
- Submit manufacturer s product literature and instructions for use to Contracting Officer s Representative for all refinishing materials.
- Prior to commencing the refinishing operations, the Contractor shall submit to the Contracting Officer a written description of the entire methods and procedures proposed for refinishing the bronze including, but not limited to: method of application, dilution of application, temperature of application, length of time of surface contact, method of rinsing surface (temperature, pressure, and duration), repetition of procedures, etc.
- The Contractor shall clean and refinish sample areas on architectural bronze components included in the work of this section as directed and for approval by the Contracting Officer s Representative. Locations of sample panels to be selected by the Contracting Officer s Representative.
- Adjust the chemical concentrations and methodologies during test panel cleaning, as directed by the Contracting Officer s Representative.
- Sample areas shall be cleaned by the Contractor using methods and materials previously submitted and approved. Cleaning and refinishing sample areas shall be performed in the presence of the Contracting Officer s Representative.
- The Contractor shall obtain written approval from the Contracting Officer s Representative of bronze cleaning and refinishing methods, materials, equipment used and sample panels before proceeding with the work of this section. For this written approval purpose, the Contractor shall allow a minimum of seven calendar days after completion of sample cleaning to permit the Contracting Officer s Representative to study the sample panels for negative reactions. Approved sample panels shall be marked and left unaltered. They shall be used as the standard for similar work throughout the project.
A. ProSoCo, Inc
755 Minnesota Avenue
P.O. Box 1578
Kansas City, KS 66117
800/255-4255 or 913/281-2700
B. Industrial Soap Co.
2930 Market Street
St. Louis, MI 63103
C. McIntyre Metal Maintenance
1615 South Broadway
Los Angeles, California
D. 3M Consumer Products Group
P.O. Box 33053
St. Paul, MN 55133-3053
612/737-6501 or 800/364-3577
E. Stanley Chemical Company
401 Berlin St.
East Berlin, CT 06023
F. Mohawk Finishing Products, Inc.
N. Amsterdam, NY 12010
G. Birchwood Casey
7900 Fuller Road
Eden Prairie, MN 55344
A. Architectural Bronze Stripper: Architectural bronze stripper shall be a thixotropic solvent/alkaline paint stripper such as Sure Klean Heavy Duty Paint Stripper (ProSoCo, Inc.), or approved equal.
B. Non-ionic Detergent: A controlled suds, silicate buffered, non-ionic, rinseless-type synthetic detergent, containing no soap, alkali, solvents, abrasives, acids or caustics such as Zyfo cleaner concentrate (Industrial Soap Co.), or approved equal.
C. Solvent: 75% toluene + 24% acetone + 19% butal acetate.
D. Cleaner: Non-abrasive metal cleaner such as Nev-R-Dull (McIntyre) formulated for bronze.
E. Degreasing Agent: Degreasing agent shall be trichlorethylene or a similar solvent.
F. Patination Agent: Patination agent shall be a commercially available conversion coating containing Selenious Acid, Cupric Nitrate, Phosphoric Acid, Ammonium Hydrogen Fluoride, Polyoxyethylene (12) Tridecyl Alcohol, and Water, such as (Birchwood Casey), or approved equal. CONSULT A SPECIALIST TO DETERMINING THE MOST APPROPRIATE PATINATION FORMULA FOR THE METAL USED.
G. Abrasive: Abrasive shall be silicon carbide abrasive pads such as Scotch-Brite (3M Company), or approved equal.
H. Flattening Agent: Flattening agent for clear protective coating shall be commercially available polyethylene dispersion (Stan Chem Inc.), or approved equal.
I. Water shall be clean, potable, non-staining and free of materials detrimental to all surfaces to be cleaned.
J. Cloth: Clean, cotton waste.
A. Stiff bristle brushes
B. Wet vacuum
- Protect surrounding materials and buildings. Products used for metal refinishing may be harmful to masonry and glass. Any damage to materials caused by the refinishing process is unacceptable and shall be repaired to the satisfaction of the Contracting Officer s Representative at no cost to the Government.
- Provide protection from water damage to building, structure, or building contents as required.
- Protect trees and plants around the building from contamination or damage. The Contractor shall be responsible for replacing with new stock any trees, shrubbery or grass damaged by the cleaning operations.
B. Surface Preparation:
- All exterior stone that may come in contact with the cleaner shall be rinsed before, during and after cleaning in order to avoid staining the stone.
- Cleaning of exterior windows shall proceed from the top of the wall downward.
- On the interior, mask off adjacent stone and dissimilar metal surfaces.
3.02 ERECTION, INSTALLATION, APPLICATION
A. Remove copper sulfate from the surfaces. See 05010-23-R for guidance. When the finish cannot be restored by removal of sulfate formation, chemically strip to bare metal and repatinate.
NOTE: PRIOR TO CLEANING, CONSULT A SPECIALIST TO DETERMINE AND DOCUMENT THE TYPE OF PATINA USED AND HAVE SPECIFICATIONS DEVELOPED FOR REPATINATION.
B. Method A
- Apply cleaner with soft cloth rubbing along grain of metal.
- Using light to moderate uniform pressure, rub with abrasive pad and solvent to clean surface.
- Interior Components: Thoroughly sponge rinse all traces of chemicals and residue with cold water. Remove waste water as work progresses by wet vacuum or other appropriate means. Do not allow water to pond on floors.
- Exterior Components: Rinse with cold water to remove all traces of detergent and residue. Rinse water pressure shall not exceed 100 psi and shall be sprayed through nozzles fitted with 15-20 degree wide tips. Nozzles shall be held perpendicular to the surface at a working distance of 1.5 to 2.5 feet.
- Reapply as required to remove persistent oxidation and stains.
- Dry surface with clean, dry cloth.
B. Method B
- Apply a heavy coat of Architectural Bronze Stripper with a brush.
- Allow stripper to remain on the surface until oxidation and copper sulfate is lifted or dissolved. Using light to moderate uniform pressure, rub with abrasive pad to clean surface.
- Thoroughly sponge rinse all traces of stripper and residue with cold water on interior components. Remove waste water as work progresses by wet vacuum or other appropriate means. Do not allow water to pond on floors.
- For exterior components, thoroughly rinse all traces of stripper and residue with low pressure cold water rinse. Refer to rinse procedure specified in Section 3.02 B.3.b. above.
- Reapply as required to remove persistent oxidation and stains.
- Neutralize surface in accordance with manufacturer s instructions.
- Allow surface to dry thoroughly.
C. Select gentlest method - A or B which satisfactorily cleans bronze as determined by sample panels.
D. Apply patination agent according to specialist's specifications and in accordance with manufacturer s instructions. Adjust concentration and dwell time in preparation of sample panels to obtain acceptable match with original patina as approved by RHPO.
E. Neutralize surface in accordance with manufacturer s instructions.
F. Apply clear protective coating. See 05010-08-P.