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 includes guidance on protecting exterior and interior architectural yellow and white bronze components with an application of lacquer.
B. For additional guidance on cleaning, refinishing and protecting bronze features, see 05010-03-R, 05010-05-P, 05010-06-P, 05010-07-P, 05010-19-R, 05010-22-R, 05010-23- R, and 05010-24-R.
C. The refinishing and cleaning of bronze is highly specialized and should be conducted under the supervision of a metal conservator. The metals conservator should verify the use of all chemicals and treatments as a result of on-site testing to ensure protection of historic metals.
D. 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= ).
- All sample panels prepared by the Contractor should be based on an existing sample in the building which is considered by the metal conservator to be close to the original architectural bronze finish, as intended by the original Architect, and approved by the Contracting Officer or the designated representative. This existing sample, referred to as the control sample, shall act as the reference for all samples prepared by the Contractor.
- 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 or the designated representative and the metal conservator. Locations of sample panels to be selected by the Contracting Officer or the designated representative and the metal conservator= .
- Adjust the chemical concentrations and methodologies during test panel cleaning, as directed by the Contracting Officer or the designated representative and the metal conservator.
- 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 or the designated representative and the metal conservator.
- The Contractor shall obtain written approval from the Contracting Officer or the designated 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 or the designated representative and the metal conservator 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.
1.03 QUALITY ASSURANCE
A. Qualifications: The objectives of architectural bronze cleaning and refinishing are to remove dirt and grime without damaging the substrate and to give all architectural bronze a uniform appearance consistent with original finish, without blotches, streaks, runs, or any other kind of spotty appearance.
B. Certifications: An independent metal conservator should be appointed to identify locations for sample areas and to monitor and review the samples prepared by the Contractor.
C. Field Samples: Sample areas for every type of architectural bronze, as designated by the Contracting Officer or the designated representative, shall be prepared and shall establish a standard for architectural bronze refinishing of that particular architectural bronze type and fabrication.
A. Stanley Chemical, Inc.
401 Berlin Street
East Berlin, CT 06023
A. Clear Protective Coating: Clear coating shall be commercially available acrylic type reversible coating such as "Incralac&quo=t; (Stanley Chemical, Inc.), or approved equal.
B. Flattening Agent: Flattening agent for clear protective coating shall be commercially available polyethylene dispersion (Stan Chem Inc.), or approved equal.
C. Water shall be clean, potable, non-staining and free of materials detrimental to all surfaces to be cleaned.
D. Cloth: Clean, cotton waste.
A. Surface Preparation:
- Clean surfaces to which protective coating is to be applied. See 05010-09-P for guidance.
- Proceed with the following procedure within four hours of cleaning.
3.02 ERECTION, INSTALLATION, APPLICATION
THE METHOD FOR REFINISHING THE ARCHITECTURAL BRONZE WILL VARY DEPENDING ON THE TYPE OF ARCHITECTURAL BRONZE, AND THE METHOD DESCRIBED BELOW IS A PERFORMANCE SPECIFICATION FOR A TYPICAL REFINISHING PROCESS. THE EXACT PROCESS WILL BE DEPENDENT ON PREPARED SAMPLES AND MUST BE DESCRIBED BY THE CONTRACTOR PRIOR TO COMMENCING WORK. THE GENTLEST METHOD WHICH EFFECTIVELY CLEANS THE ARCHITECTURAL BRONZE SHOULD ALWAYS BE USED.
A. All superficial accretions, oils, and un-reacted chemicals must be thoroughly rinsed from the surfaces prior to coating application using a non-ionic detergent.
B. Surfaces being treated must be thoroughly dried.
C. Apply clear protective coating by spray in three successive =AB mil, even coatings for a total dry thickness of 1-AB mils, for interior finishes. The exterior architectural bronze should be covered with a minimum of 2 mil thickness of the clear protective coating.
NOTE: APPLICATION MUST FOLLOW THE CLEANING OPERATIONS WITHIN FOUR HOURS. ALLOW MINIMUM 20 MINUTES DRYING TIME BETWEEN COATS.
D. Brush-applying coating is not permitted. (Brush-applied coatings will not provide complete coverage of uniform thickness.)
E. Add the flattening agent to the final coating to match the sheen of the original rubbed finish, as shown on the control sample and approved by the Contracting Officer or the designated representative and metal conservator in the form of the Contractor's sample.
A. To be carried out by janitorial services, supervised by the Contracting Officer's representative. Anything beyond cleaning should be referred to the metal conservator for immediate repair.
- For regular monthly maintenance and cleaning of the architectural bronze, apply a non-ionic detergent to all surfaces using a sponge.
- Thoroughly rinse the surfaces with water and dry with a clean dry cloth.
- Protect all surrounding materials from water damage.