These potential shortcomings should be considered when attempting to artificially duplicate a weathering process which may take from five to seven years in coastal or industrial environments, longer in rural areas, and may perhaps never develop in some climates and atmospheres.Īrtificial patinas for architectural applications such as copper roofs, grilles, and statues have an inherent requirement which dictates that the solution has to be one which can be brushed or sprayed because of the large surface areas normally involved. In artificially producing or accelerating the formation of a patina, success seems to depend on the manner in which the solutions are applied, the weather conditions under which the treatment is carried out, and perhaps most important, on the climate to which the treated surfaces are exposed.īecause of the number of variables involved, chemically induced patinas are prone to lack of adhesion, excessive staining of adjacent materials or inability to achieve reasonable color uniformity over large surface areas. The basic chloride salts of copper are not only fairly soluble, but photosensitive as well. In seacoast locations, chloride salts may form an essential part of the patina film. Carbonate and chloride salts of copper may also be present in varying concentrations. In natural patination the major coloring agent in the film is basic copper sulfate. Because of the time required to achieve this, much research has been done on artificial patination, with varying success. The much admired natural protective coating of a blue-green patina characterizes older copper roofs, including ancient cathedrals as well as bronze statues and other copper metal surfaces exposed to the weather.
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