Applying Hot Wax To Outdoor 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 applying a hot wax sacrificial coating to outdoor bronze. This barrier helps prevent harmful atmospheric pollutants from contacting and reacting with the surface. The application of hot wax to a heated surface, followed by sacrificial coatings of cold paste wax should provide the maximum bonding and protection.
  2.  Apply as needed to restore maximum protection following the removal of older wax coatings.
  3. For general information on the characteristics, uses and problems associated with bronze, see 05010-03-S.



  1. (search engine for the chemical industry)
  2. Museum Services Corporation (MSC)
  3. Conservation Support Systems (CSS)


NOTE: The wax product selected should be a synthetic microcrystalline wax including natural carnauba wax forming a blend.

  1. Outdoor Sculpture Wax (MSC), or approved equal
  2. Sculpture Wax (CSS), or approved equal.
  3. Cosmolloid 80 H (if needed per manufacturer's product guidance)
  4. Benzotriazole (BTA) corrosion inhibitor (MSC or CSS), or approved equal (if needed per manufacturer's product guidance)
    NOTE: BTA has been identified as a chemical with health hazards; following manufacturer's Material Data Safety Sheet for guidance for safe use.
  5. 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.
    5. Available from construction specialties distributor, hardware store, paint store, or printer's supply distributor.
  6. Rags, clean soft, lint free, unsized, (such as old T-shirts or toweling)
  7. Paper towels, lint free, such as Kimwipes (Fisher Scientific Company), or approved equal.


  1. Portable, hand-held propane torches
  2. Hogshair brushes



  1. Protection:
    1. General: Comply with recommendations of manufacturers of waxes and coatings for protecting building surfaces against damage from exposure to their products.
    2. Protect adjacent surfaces from contact with run-off from hot oily waxes by covering them with liquid strippable masking agent or polyethylene film and waterproof masking tape. Apply masking agent to comply with manufacturer's recommendations. Do not apply liquid masking agent to porous surfaces.
    3. Rags should be used to intercept any oily wax run- off, so it does not come in contact with adjacent materials.


  1. For the wax product chosen, follow the manufacturer's product guidance in its use.
  2. Heat the wax until dissolved into a liquid.
  3. Add BTA, if needed according to the manufacturer's guidance, to make 3% solution (97% wax to 3% BTA).
  4.  Add mineral spirits to wax solution as it cools to make a creamy, paste wax mixture.
  5. Heat the surface of the bronze evenly with the portable propane torches.
  6. Brush the wax onto the heated surface, thoroughly coating the surface. Take necessary precautions to contain all drips with clean rags or paper towels to prevent the hot oily wax from coming in contact with adjacent materials.
  7. Allow to cool and dry thoroughly.
  8. Apply two coats of paste wax (see 05010-06-P "Applying Cold Microcrystalline Wax to Bronze Sculpture").