What Chemicals Cause Patina in Copper?
Patina is the greenish or bluish color that develops on copper and some other metals through exposure to natural elements over time. The natural patination process on copper can take many years, and it is brought about through exposure to carbonate, chloride salts and sulfate, though not necessarily all three at the same time. Patina can form when any one of these elements are present. Different colors, including brown, green and blue, will be produced, as will different intensities of those colors, depending on what concentration or combination of carbonate, chloride salts or sulfates are present. Patina occurs through oxidation, when oxygen starts a reaction with the chemicals present. It is the same process that produces rust.
Speeding up the Process
It is possible to create a patina by exposing copper to the same chemical elements rather than waiting for the process to take place naturally. Formulas vary, but ammonium chloride crystals, copper sulfate and ammonium sulfate can all be used to achieve the affect. The chemicals are usually mixed with concentrated ammonia and water to get the right results. A mixture of table salt, household ammonia and vinegar can also be used to create a patina. Just wipe the mixture on the copper with a lint-free cloth or spray it on in a fine mist.
Maria Magher has been working as a professional writer since 2001. She has worked as an ESL teacher, a freshman composition teacher and an education reporter, writing for regional newspapers and online publications. She has written about parenting for Pampers and other websites. She has a Master's degree in English and creative writing.