![]() ![]() Avoid cleaners which leave a coat of oxide on the copper surface.įollow cleaning with a thorough rinsing to remove all traces of the cleaning compound. Cleaners of the trisodium phosphate type should be satisfactory. However, it is always advisable, particularly if the coloring is to be done immediately after installation, to go over the surface with a commercial chemical metal cleaner. This involves removal of the residual film of oil left on copper and brass sheets from mill rolling operations, and fingerprints and dirt deposited on the surface during handling and installation.Ī few hard rainstorms may clean the surfaces sufficiently to start operations. The copper surfaces to be colored must be clean, as any dirt, oil or grease on the surface will interfere with the chemical action of the solution. 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 above remarks also contradict the beliefs that food, which proceeds from own horticulture by using copper soil-tilling machines, could be a danger in the nutrition of infants.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. Neither the concentration of possibly available acids by food composting nor the duration of the contact between the metal and these acids would facilitate the formation of poisonous verdigris. Verdigris develops due to longer effect of acids on copper. It is out of the question that the food remainders mentioned in the definition above, which can be found in the compost and also be regarded as possible source of organic acids, are the ones causing the verdigris in the practical horticulture. In reality a protecting patina layer forms on the devices this layer protects them and guarantees a long life span. Unfortunately these two terms are often confounded and that is why it is frequently said that poisonous verdigris might develop itself on copper garden-devices. Food remainders (fruit acid, acetic acid) as well as animal eliminations (urine acid) are included in the above-mentioned category. It develops as a result to longer influence of weak acids with mostly organic compounds. ![]() Is a mixture of basic green or blue copper acetates, which settles on copper or brass. In its salient green form the patina, dependent on rain quantity and water composition, appears after approximately 8 to 15 years on flat surfaces that are strongly exposed to rain. Patina protects copper against decomposition. ![]() This layer forms when in reaction with the carbon and sulfur dioxide contained in air. Is a grey-green surface layer on copper and copper alloys, which consists of basic carbonates and sulfates. ![]()
0 Comments
Leave a Reply. |