Patina green copper cage4/25/2023 ![]() Etched texture is possible on copper alloys with ammonia and vinegar. Again, contact points are the focus of action, an example being the polka dots produced by hamster cage cedar shavings. Damp (not wet) wood shavings or other porous materials work well for differential patination/etching of surfaces. A combination of salt and ammonia fumes makes for fast results but adhesion is not as good as with the cupric nitrate patina. Salt functions as a direct corrosive agent. Ammonia and vinegar produce good results as fumes. Patination agents included in this paper are clear household ammonia, vinegar, table salt and cupric nitrate. Burial in alkaline or acidic earths has also been used to create patinas and may be considered a kind of paste application. Diet and physical condition would add minerals, salts and chemical compounds to the solution and subtly affect metal surfaces. I have heard of a Korean metalsmith who had over 40 dated jars of aged urine in his workshop, the older ones being more prized. Works have been buried in manure, coated with pastes containing urine or sealed in urine atmospheres. The oldest traditional method of obtaining green patinas on copper alloy surfaces was to expose them to urine, often aged to developed a stronger ammonia content. The best durability, color control and speed of application are produced using solutions and patinas that rarely occur in nature. All of them can be produced faster with chemical treatments. ![]() These patinas take four to 30 years to develop well, depending on the location. Varying conditions produce combinations of these and others. Industrial environments tend to produce a copper sulfate base, the ocean a copper chloride base and the mountains a copper carbonate base. Natural patinas formed on copper alloys vary with the environment. They must adhere well to the metal and be properly sealed. When used in jewelry, patinas should be isolated from all surfaces in skin contact. The irresponsible use of patinations in the fashion industry is likely to lead to a backlash when the first major skin reactions occur in customers. They must be used if the object will be in body contact. Protective sealers are often used with patinas. Many patinas are toxic if ingested and may cause skin irritation in close or constant skin contact. Patinated surfaces should not be worn in contact with the skin or used in anything connected with food. ![]() Pin, copper, silver fused to surface acting as resist to ammonia fumes 24k gold, tsavorite, Walrus ivory, 7cm d., 1986 As this paper is intended as an introduction to metal coloring, basic procedures are emphasized. Since there are thousands of solutions, pastes and atmospheres that affect metal surfaces, there is often more than one method of achieving the same or similar color on a specific metal. This abbreviated paper addresses the need for simple, less toxic solutions for small-scale studio use.
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