Q. How do I give a copper fire pit an artificial green patina?
A. The tarnish that develops on copper over time is what makes the Statue of Liberty look green instead of brown, and it’s a popular look for many copper architectural elements. It takes a lot of time for copper to achieve the look naturally, so “artificial patination” is an attempt to speed up the process, although the procedure is known to vary greatly in success. According to the Copper Development Association, artificially accelerating the formation of a patina depends on the manner of solvent application, weather conditions and the climate. Because of the many variables, chemically induced patinas are prone to lack adhesion and have problems achieving uniform color over large surface areas. Professional processes for accelerated patina formation use either a sulfate solution of chloride salts.
However, for a small DIY project, you might try the following “home remedy” (untested by the EHT staff). Use liquid dish soap and water to clean the surface thoroughly, then rinse off. In a spray bottle, mix together white vinegar (2 parts), non-detergent ammonia (1-1/2 parts) and non-iodized salt (1/2 part). Spray on a light coating of Windex (don’t wipe off). Spray the vinegar/ammonia/salt mixture onto the copper and allow it to dry overnight. If you are in an arid climate, cover with plastic to keep in the moisture. You may need several coats of the patina mixture to achieve the desired effect.