Repairing a Scratched or Worn Incralac Coating on Bronze

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.



  1. This procedure includes guidance on selectively repairing damaged or worn areas of the protective acrylic resin coating (Incralac) on bronze.
  2. Incralac is designed to be applied by spray. Brush applied coatings are not recommended, as they tend to be thicker and contain flaws created by the movement of the brush hairs through the resin during application. Both factors reduce the durability of the coating. When a brush-applied coating begins to deteriorate, it will deteriorate first along the brush-hair excursions and thereby produce numerous crevices in the coating where corrosion can occur, visible as a fine network of green hairline striations.
  3. Perform repair work as needed when the Incralac coating is damaged or missing.
  4. For general information on the characteristics, uses and problems associated with bronze, see "Bronze: Characteristics, Uses and Problems".



  1. Stanley Chemical Co.
    East Berlin, CT 06023
  2. Conservation Materials
    Sparks, NV
  3. Maas & Waldstein Co.
    Carlstadt, NY
  4. Custom Aerosal Packaging
    Piqua, OH
  5. Fisher Scientific Company
    Pittsburgh, PA
  6. Procter & Gamble Co.
    Cincinnati, OH


NOTE: Chemical products are sometimes sold under a common name. This usually means that the substance is not as pure as the same chemical sold under its chemical name. The grade of purity of common name substances, however, is usually adequate for stain removal work, and these products should be purchased when available, as they tend to be less expensive. Common names are indicated below by an asterisk (*).

  1. Acrylic lacquer such as "Incralac" (Stanley Chemical Co.), (Conservation Materials), (Maas & Waldstein Co.), (Custom Aerosal Packaging), or approved equal. Available in spray cans or 5-gallon drums.
  2. Polyethylene dispersion, added to final Incralac coating to produce desired degree of matt/glossy appearance, (71X-202 polyethylene dispersion) (Stanley Chemical Co.), or approve equal.
  3. Mineral Spirits:
    1. A petroleum distillate that is used especially as a paint or varnish thinner.
    2. Other chemical or common names include Benzine* (not Benzene); Naphtha*; Petroleum spirits*; Solvent naphtha*.
    3. Potential Hazards: TOXIC AND FLAMMABLE.
    4. Safety Precautions:
      2. ALWAYS wear rubber gloves when handling mineral spirits.
      3. If any chemical is splashed onto the skin, wash immediately with soap and water.
  4. Available from construction specialties distributor, hardware store, paint store, or printer's supply distributor.
  5. Mild detergent such as "Ivory", "Joy" or "Thrill" (Procter & Gamble Co.), or approved equal. Available in supermarket or drugstore.
  6. Clean, potable water
  7. Sponges and soft towels or rags


  1. For large areas of coating deterioration, bulk application with power spray equipment is more effective. The following equipment is recommended
    1. Spray gun, Binks or DeVilbiss with accessories; for example, DeVilbiss bleeder, external mix gun with cup, or approved equal.
    2. Air compressor, small, portable, either gas (for exterior use) or electric (if electricity is accessible), or electric compressor powered by a portable generator.
    3. Accessories: air hoses adequate for reaching all parts of the metal, couplers, repair kit for spray gun, small moisture traps.
  2. Organic vapor masks, basic safety equipment to protect operator from breathing vapors or organic solvents during spray application.
  3. Goggles, to protect operator's eyes from organic solvent and Incralac.
  4. Gloves, neoprene rubber or polyethylene disposable gloves. Skin contact with solvent or Incralac should be avoided.



  1. If bronze has a protective wax coating over the Incralac, use mineral spirits or other appropriate solvent to remove wax from affected area.
  2. Wash area to be recoated to remove all surface dirt, grease and foreign matter including flaking Incralac coating.
    1. Wipe the surface with a clean cloth saturated in clean, clear water and mild detergent. DO NOT FLOOD ENTIRE SURFACE, SIMPLY WIPE AFFECTED AREA.
    2. Thoroughly rinse the surface with clean, clear water and allow to dry.
  3. Apply clear protective coating within 4 hours of cleaning operations. For small areas use Incralac in a spray can. Large areas will require the use of power spray application equipment.
    1. Apply first coat in a thin mist. Allow to dry.
    2. Apply two additional wet coats, allowing minimum thirty minutes drying time between each coat.
    3. Minimum thickness of Incralac coating shall be 1 mil.
  4. If Incralac coating has a protective wax finish, apply wax as directed in procedure "Applying Cold Microcrystalline Wax to Bronze".