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: | 02/24/2012 |
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 bronze which suffers from dents, scratches, small holes or nicks. 1. For guidance on cleaning, polishing and removing corrosion from bronze, see 05010-01-P. 2. For general information on the characteristics, uses and problems associated with bronze, 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 SYSTEM DESCRIPTION A. The natural beauty of the bronze should be well preserved. The bronze should be intact, in good condition, without any signs of deterioration (corrosion by the action of the atmosphere and acids derived from organic growths, scaling, pitting, or severe rust). There should be no missing elements. 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 63-1500 Filler and Surfacer (a solventless catalyzed 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 bronze, first examine the surface(s) to determine the extent of the work required. 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 bronze 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 Bronze: 1. Clean the bronze 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. 6. If the bronze piece cannot be salvaged, it should be replaced with new bronze or other replacement material (bronze plated) of the same weight, configuration, and temper hardness. RHPO MUST APPROVE REPLACEMENT. D. Missing pieces: Missing pieces can be reproduced by casting. END OF SECTION |
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