Restoration of Bronze and Copper Ornamental Metal Finishes
Historic Finishes for Architectural Bronze, Brass and Copper Restoration and Replication
Architects, conservators and restoration and preservation experts are often faced with the dilemma of bronze, brass or copper monuments or architectural elements that have had the surface patina and finish marred or discolored.
Historical BronzeWorks can help with the restoration of the finish to ornamental metalwork, as well as the replication and replacement of any missing elements. If your project involves restoration, reproduction or repair of historically significant metalwork or its finish, please contact us for assistance. We work with preservation architects and building conservators to assess the condition of the ornamental metals and help prepare recommendations for their treatment.
The first step is to understand the problems with the bronze monument or architectural elements. If the problems are minor, such as surface corrosion, we can assist with a proper cleaning and the reapplication of proper protective patinas. If there are major problems with the ornamental metals, such as missing pieces or extensive damage, we can assist with a complete scope, including determining the original metal, creating outline specifications, details and shop drawings, models, casting and installation.
Before work begins, a physical inspection is done of every section of the ornamental metal construction. The condition of the building or monument is recorded by drawings, photographs, and written descriptions. Once work begins, each step of the preservation, restoration and repair or replacement is documented.
The successful conservation of bronze and copper architectural elements and monuments depends on the accurate diagnosis of their condition and the selection of proper cleaning, repair and replacement processes. If your project needs the assistance of a company that specializes in quality architectural, artistic and historical bronze, copper, brass and ornamental metals restoration and replacement, please contact us. We are here to help.
Restoration of Brown Statuary Finishes
The statuary finish is a conversion coating. A conversion coating is a finish created by changing or converting the surface of the bronze, brass or copper to a protective oxide or sulphide of the metal, or by precipitating a surface film onto the metal.
Brown and black surfaces on architectural bronze, brass and copper are created by production of a sulphide coating. The coating is created by applying an alkaline sulfide solution to the bronze.
For historical bronze and copper a mixture of potassium polysulfides and thiosulfate (potassium sulfured) was used. Originally known as “liver of sulpher”, the compound should only be used on bronze or copper restoration by people experienced in its use. A small amount is dissolved in warm water and applied to the prepared bronze surface.
- The sulfur compound reacts with the surface of the bronze to produce light, medium or dark browns, grays and blacks.
- Color depends on the base metal alloy (copper, bronze, brass or other) the concentration of the sulphide coloring solution, the number of applications, surface preparation and the final buffing.
- The fumes and handling of the material can be somewhat dangerous and it should only be used with care by experienced applicators.
- The bronze finish can last indefinitely if protected by oiling, waxing or, more permanently, by a good top coat of clear lacquer.
- Sulfide films on ornamental metals often require preparation with a wet or dry scratch brushing.
- Color contrast in ornamental metals can be produced by buffing with a pumice paste or a polishing compound.
Restoration of Green Patina Finishes on Ornamental Metals
The blue-green patina which characterizes older bronze sculptures, monuments and architectural elements that have been exposed to the weather is copper sulphate.
When the natural patina is damaged, artificial patination can be applied to speed the process and recreate the finish.
- The major coloring agent in green patina is copper sulfate.
- In marine and seacoast environments, chloride salts often form an essential part of the patina.
- Patina results depend on proper application, weather conditions and the climate to the patina surfaces are exposed to.
- The bronze or other ornamental metal surfaces must first be cleaned before application of the patina.
- Proper bronze patina is both attractive and a self healing protective film.
Bronze architectural elements and ornaments are cast with natural materials and harmonize with other natural materials. Patinas are part of the beauty and classical appeal of the bronze. If your project needs the restoration and replacement of architectural bronze, copper or other ornamental metals in architecture, art or monuments, please contact us. We are here to assist you.