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Historic Preservation - Technical Procedures

Spectitle:

Refinishing Bronze Features

Procedure code:

0501024R

Source:

National Capitol Region Specifications

Division:

Metals

Section:

Metal Materials

Last Modified:

02/24/2012

Details:

Refinishing Bronze Features



REFINISHING BRONZE FEATURES


PART 1---GENERAL

1.01     SUMMARY

        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:

             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).  

1.02     SUBMITTALS

        A.   Product Data:  
       
             1.   Submit manufacturer s product literature and
                  instructions for use to Contracting Officer s
                  Representative for all refinishing materials.
             
             2.   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.

        B.   Samples:
       
             1.   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.
                 
             2.   Adjust the chemical concentrations and
                  methodologies during test panel cleaning, as
                  directed by the Contracting Officer s
                  Representative.
                 
             3.   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.
                 
             4.   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.
                 
             
PART 2---PRODUCTS

2.01     MANUFACTURERS

        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
             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.
             Route 30 N.
             Amsterdam, NY  12010

        G.   Birchwood Casey
             7900 Fuller Road
             Eden Prairie, MN 55344

2.02     MATERIALS

        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.

2.03     EQUIPMENT

        A.   Stiff bristle brushes

        B.   Wet vacuum


PART 3---EXECUTION

3.01     PREPARATION

        A.   Protection:

             1.   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.
             
             2.   Provide protection from water damage to building,
                  structure, or building contents as required.
             
             3.   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:

             1.   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.
             
             2.   Cleaning of exterior windows shall proceed from the
                  top of the wall downward.
             
             3.   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
       
             1.   Apply cleaner with soft cloth rubbing along grain
                  of metal.
             
             2.   Using light to moderate uniform pressure, rub with
                  abrasive pad and solvent to clean surface.
             
             3.   Rinse
             
                  a.   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.
                 
                  b.   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.
                 
             4.   Reapply as required to remove persistent oxidation
                  and stains.
             
             5.   Dry surface with clean, dry cloth.
             
        B.   Method  B
             
             1.   Apply a heavy coat of Architectural Bronze Stripper
                  with a brush.
             
             2.   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.
             
             3.   Rinse:
             
                  a.   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.
                 
                  b.   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.
                 
             4.   Reapply as required to remove persistent oxidation
                  and stains.
             
             5.    Neutralize  surface in accordance with
                  manufacturer s instructions.
             
             6.   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.
       
                             END OF SECTION