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Historic Preservation - Technical Procedures

Spectitle:

Repairing Minor Deterioration Of Brass Features

Procedure code:

0501002R

Source:

Hspg Prepared For Nps - Sero

Division:

Metals

Section:

Metal Materials

Last Modified:

01/10/2014

Details:

Repairing Minor Deterioration Of Brass Features



REPAIRING MINOR DETERIORATION OF BRONZE FEATURES


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on repairing metal
         which suffers from dents, scratches, small holes or
         nicks;and treating other minor damage on architectural metals commonly found in historic buildings. 

        Significant metal elements, sculptural bronze as example, require the care of a qualified conservator. 

         1.   For guidance on cleaning, polishing and removing
              corrosion from metal, see 05010-01-P.

         2.   For general information on the characteristics,
              uses and problems associated with metal, see
              05010-03-S.

    B.   Safety Precautions:

         1.   Workers should take precautions to prevent epoxies
              and their components from contacting the skin.

         2.   Provide protective clothing which must be worn and
              protective creams for exposed skin areas.
              Accidental contact with unprotected skin to these
              materials must be treated immediately by washing
              with soap and water, never with solvents.  

         3.   Exercise care to avoid skin contact to tool
              cleaning solvents and to provide adequate
              ventilation for clean-up operations.

    C.   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 SUMMARY DESCRIPTION

    A.   This procedure is for repair of minor surface weathering 
         or damange on otherwise sound architectural metals.
         

PART 2---PRODUCTS

2.01 MATERIALS

    A.   Epoxy such as one of the following:

         1.   Auto body putty - available from auto body stores,
              or from hardware stores.

         -OR-

         2.   Resin-impregnated fiberglass.  Fiberglass comes in
              mesh or strands (mesh is best for small holes) -
              available from marine supply stores.

         -OR-

         3.   Polyester or epoxy resin, such as Tnemec Series 215-Surfacing Epoxy.
              (a modiried polyamine epoxy), or approved equal - available in cans from
              marine supply stores.

    B.   Clean, soft wiping cloths

2.02 EQUIPMENT

    A.   Eye and skin protection

    B.   Gloves and protective gear

    C.   Stiff bristle brushes

    D.   Hammer


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Before proceeding with steps to repair the metal, first
         examine the surface(s) to determine the extent of the
         work required. Document with description and photos the existing conditions prior to treatment. Look for:

         1.   Wear - especially moving parts.

         2.   Broken, cracked, missing distorted, or loose parts.

        3.   Coating failures such as chips, peeling, checks,
              bubbling, and wear.

         4.   Rust corrosion - caused by moisture, deicing salts,
              acids, soils, gypsum plasters, magnesium
              oxychloride cements, ashes, clinkers, and sulfur
              compounds.  Determine the source of the moisture
              which causes the deterioration.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   For perforated spots and thinned surrounding areas:  Soft
         solder with a patch large enough, and cut appropriately,
         to cover the entire area.  See 05010-07-R for guidance on
         soldering.

    B.   For Dents and Scratches:

         1.   If the backside of metal feature is accessible and
              not too thick, gently hammer the dent back in
              place.  

         2.   For severely damaged sections, cut out, recast, and
              reattach by riveting or brazing.  Brazing is a form
              of soldering that uses a bronze or brass filler
              metal.

         3.   Buff scratches to match the original finish and
              texture.  See 05010-01-P.

    C.   For Small Holes, Nicks, and Minor Imperfections in
         Painted Metal:

         1.   Clean the metal surface of any dirt, grease or
              corrosion.  See 05010-01-P for guidance.

         2.   Prime metal before applying epoxy, and allow to
              dry.

         3.   Fill damaged areas with an epoxy patching compound.

              NOTE:  EPOXY USED SHOULD BE COMPATIBLE WITH ANY
              PAINTS, LACQUERS OR WAXES USED.

              a.   Mix and apply epoxy according to manufacturers
                   instructions.  

              b.   Allow to cure and dry thoroughly.  

              NOTE:  EPOXY SHOULD CURE TO A SMOOTH FINISH,
              REQUIRING NO FURTHER SANDING OR GRINDING.

         4.   Apply a second coat of primer.

         5.   Apply finish coat of paint to the epoxy patch area.

         6.   If the metal piece cannot be salvaged, it should
              be replaced with new similar metal or other inert replacement
              material (as example: bronze plated) of the same weight,
              configuration, and temper hardness.  RHPO MUST
              APPROVE REPLACEMENT.

    D.   Missing pieces:  Missing pieces can be reproduced by
         casting.

   E.   Project Closeout: Document the treatment results with description and photographs for building files.



                         END OF SECTION
 


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