Cleaning of copper alloy objects

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 judgment 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.

Part 1 – General

1.01 Description

1. This specification provides guidance for cleaning and applying protective coatings to copper alloy (brass and bronze) objects.
   1. This specification has been developed for use on historic properties (defined as any district, site, building, structure, or object that is listed in or eligible for listing in the National Register of Historic Places) and provides an overview of accepted practices. Site-specific specifications, when appropriate, will be provided by the Architect.
   2. All work described herein and related work must conform to the Secretary of the Interior’s Standards for the Treatment of Historic Properties.
   3. The Contractor shall provide all labor, material, equipment, and operations required to complete the rehabilitation work indicated herein.
   4. All work described herein and related work must have the approval of a Cultural Resources Manager, Conservator, Historic Architect, or other professional who meets the standards outlined in the Secretary of the Interior’s Standards – Professional Qualifications Standards pursuant to 36 CFR.

1.02 Section includes

1. General cleaning of copper alloy objects
2. Application of a clear coating to brass or bronze

1.03 Related sections

1. Section 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections and should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from GSA Historic Preservation:
   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)
   9. Historic Building Treatment Procedures

1.04 Quality assurance

1. The contractor performing the work described in this Section shall have a minimum of five years experience in brass and bronze cleaning and restoration and shall have successfully completed at least three projects of similar scope within the previous five years. He/she shall demonstrate a working knowledge of The Secretary of the Interior’s Standards for the Treatment of Historic Properties with Guidelines for Preserving, Rehabilitating, Restoring & Reconstructing Historic Buildings.

1.05 Submittals

1. The contractor shall submit to the Architect or GSA Approving Official:
   1. A detailed description and schedule of the areas to be treated, including an assessment of the problem surfaces, any necessary testing, and proposed general cleaning techniques, waxing procedures, etc., for approval once cleaning test areas are completed and approved.
   2. The manufacturer’s product literature for all proprietary products. If a custom wax formula is used, all ingredients must be documented and submitted for approval as with proprietary formulas. Product literature shall include specification data, Safety Data Sheets (SDS), and instructions for storage, handling, and use.
   3. A project safety plan to include at minimum: any personal protective equipment to be used by the contractor’s staff such as disposable clothing, gloves and safety glasses, procedures for emergencies and accidents, documentation of staff training in use of equipment and/or chemical products as required by the manufacturers.

1.06 Testing and mockups

1. Contractor, at inconspicuous locations designated by the Project Team and GSA HP, shall perform small test patches (no larger than 6 inches by 6 inches) for all products to be used. Testing will determine the best method(s) to perform the work and ensure that the chosen products do not cause harm. The “best method” shall be defined as that which successfully cleans and provides a protective coating with no, or minimal, damage to the brass or bronze substrate.
2. Following testing, mockup panels shall be created (mockup panels may incorporate successful test patches) using the chosen methods. Size and location of mockup panels shall be determined by the project Team and GSA Historic Preservation.
3. The methods used, their application, etc. shall be in accordance with manufacturer’s instructions and shall duplicate those procedures proposed for the overall brass or bronze cleaning and protective coating process. GSA Historic Preservation shall conduct a thorough evaluation of each method after work is complete to determine the best method for the overall work.
4. The mockup shall include an evaluation of the materials and techniques proposed for the protection of surrounding areas from the chemicals used to clean and coat the bronze. Evaluation must include an evaluation of the method to be used to collect the cleaning effluent.
5. For proprietary cleaning systems, a representative of the cleaning materials manufacturer(s) shall be present during the preparation and application of the test areas.
6. Approved mockups shall become part of the work and shall serve as the quality standard for all similar work.
7. Any testing, demonstrations, or mockup that is rejected by the project team shall be removed in its entirety without damage to the surrounding masonry and a new demonstration/mockup shall be performed for the project team’s review.

1.07 Delivery, storage, and handling (as applied to products and materials)

1. The Contractor Shall:
   1. Deliver restoration cleaning and testing materials and proprietary products to the project site in manufacturer’s or distributor’s packaging, undamaged, complete with application instructions and Safety Data Sheets (SDS)
   2. Transport and store cleaning agents, chemicals, and solvents within the temperature range recommended by the manufacturer and away from direct sunlight. Handle all materials according to manufacturer’s instructions.
   3. Collect and dispose of waste material, packaging, debris, and effluent associated with the work in accordance with local, state, and federal environmental regulations.

1.08 Safety

1. The contractor shall only use chemical products whose safety data sheets (SDS) have been reviewed and considered acceptable by the Government. Any project surfaces containing lead-based paint, as disclosed by the Government, shall be handled by the contractor in accordance with OSHA (29 CFR 1926.62), EPA (40 CFR 261) and State regulations. Any lead-based paint or coating that is removed in a project resulting from this scope shall undergo Toxicity Characteristic Leaching Procedure (TCLP) testing by the contractor. The contractor shall dispose of any lead-paint waste as hazardous if it fails the TCLP.
2. Any paint or coating required to be removed which has not been disclosed by the Government to contain lead, shall be tested for lead by the contractor. All paints or coatings testing positive shall be handled and disposed of as lead-based.
3. The contractor shall isolate the work area with cones, tape or similar means as possible for the duration of the project, to prevent unauthorized individuals from entering the immediate work area.
4. For any work required on elevated surfaces (4 feet or more above the ground) the contractor shall install and use any ladders, scaffolding or platforms in accordance with OSHA regulations (29 CFR Subpart M).

1.09 Project/site conditions

1. It is generally preferable that brass and bronze features be uninstalled prior to cleaning.
2. The work of this Section shall be executed when all areas of the brass or bronze are at a temperature within the product manufacturer’s recommended temperature range for application. If the copper alloy features can not be uninstalled for cleaning then any exterior work shall not commence when rain, snow, or below-freezing temperatures are expected within the next 24 hours. All surfaces shall be free of standing water, frost, and ice.
3. The contractor is responsible for protecting existing adjacent areas and materials during the execution of the work and shall provide all necessary protection and follow all necessary work procedures to avoid damage to existing material assemblies and vegetation not a part of the work of this Section.
4. At a minimum, the contractor shall:
   1. If work is to be performed in situ, contractor must protect woodwork, glass, metal, and any material adjacent to brass or bronze areas to be cleaned from overspray and possible chemical or water damage from cleaning operations. Cover all window openings with waterproof plastic to prevent leakage to the building interior.
   2. Protect surrounding vegetation from runoff during cleaning operations.
   3. Exterior work areas should be accessed from the exterior only. Under no circumstances are hoses to be run or equipment transported through the building during exterior cleaning operations.
5. If applicable, the contractor shall coordinate treatment operations with the other trades involved in exterior and interior restoration work, including but not limited to masonry restoration, sealing, and painting. Masonry cleaning is to be completed prior to restoration of windows, doors, and metalwork, and prior to any exterior painting in the affected areas.
6. All contractor personnel performing treatment operations shall be provided by the contractor with gloves, respirators, protective clothing and any other personal protective equipment (PPE) as recommended by the manufacturer of the products used during the work and required by local, state, and federal regulations.

Part 2 – Products

2.01 Cleaning of lighting fixtures

1. Erect a stable working platform, which will allow easy access to all elements of the lighting fixture and hangers. Support fixture so that no additional pressure will be placed on its hangers during the cleaning operation.
2. Remove all bulbs and removable glass elements. Clean with a mild soap and water. Rinse and dry thoroughly.
3. Clean glass elements which cannot be safely removed inside and out. Using a small nozzle, carefully vacuum dirt from the inside of the fixture and wash the glass with a mild soap and water, rinse thoroughly with clear water and dry with a clean, soft cloth.
4. Follow procedure for cleaning of copper alloy components

2.02 Cleaning of copper alloy objects

1. Investigation and methods selection
   1. Identification of substrate conditions, previous treatments, and any existing coatings. Testing may require additional technical expertise from a materials scientist, architectural conservator, microbiologist, and/or other technical expert. The contractor shall choose the gentlest method possible to clean the copper alloy, brass or bronze, and remove any existing coatings without damaging the substrate.
   2. The contractor shall conduct cleaning, coating removal, and protective coating application test patches, in unobtrusive locations on the surface to be cleaned. The purpose of the test patch is to determine the gentlest, most effective method to clean, strip and apply protective coatings to the brass or bronze. Several cleaning, stripping and coating methods are preferably tested side by side in small patches, size and location to be determined by GSA Historic Preservation and the project team.
   3. Damage to the brass or bronze, including its patina, cannot be addressed by cleaning, and is therefore not covered under this section.
   4. Existing conditions and processes must be documented before, during, and after work.
2. Cleaning Methods:
   1. Brush away all dirt and debris with dry, clean, soft bristle brushes. Wrap metal ferrules of brushes with duct tape to avoid scratching the brass or bronze. Use small natural bristle brushes and bamboo skewers to dislodge debris from crevices. Metal tools and dusting cloths shall not be used.
   2. Copper alloy objects are not to be submerged in water and liquid shall not penetrate rims, edges or hollow parts such as handles.
   3. Remove old polish residue, often found in recessed areas. Apply a few drops of dilute (in distilled water) clear, unscented dishwashing detergent, with a soft bristle brush or cotton swab, to the area. Agitate with a soft bristle and rinse with cotton swabs dampened with distilled water.
   4. Remove waxy or oily accretions, finger prints, and light tarnish, by wiping the surface with mineral spirits applied to cotton. Change cotton often. A rolling motion should be used, not rubbing.
   5. Copper Alloy objects should usually not be polished. Wipe the objects gently with clean flannel or cotton changed frequently to avoid scratching the surface.
      1. Light tarnish may be removed by wiping the surface with cotton moistened with denatured alcohol.
      2. If polishing is necessary the least abrasive method should be used. Start with a paste of precipitated calcium carbonate and denatured alcohol applied with a soft cloth. A jewelers’ cloth may also be used.
      3. Commercial cleaners may not be used.

2.03 Application of clear coat

1. WAX
   1. Cold Wax
      1. Microcrystalline paste wax should be applied with a soft, clean, dry cloth rubbed over the surface of the object. Use only a small amount of wax and ensure complete coverage. Allow the wax to dry and then buff the wax with a soft brush.
   2. Organic Resin Coating
      1. This may be applied by a qualified individual, such as a conservator, for longer lasting protection.

2.04 Final report

1. The Contractor Shall:
   1. Provide a final report of completed work, including all approved submittals and photographs of the objects that were taken before, during, and after the work.
   2. Provide a written summary of the project and results upon final inspection and approval. The summary shall include a discussion of steps taken or new findings not specified in the initial documentation. Summary should also include any applicable ongoing care and warranty requirements.