Why does copper turn green?

 

Have you ever wondered why copper does copper turn green?  When left outdoors to the elements, copper transforms from a bright, shiny new penny shade, to a burnished brown, and finally to a distinct green color and makes it such a great choices for products such as copper awnings.


This unique characteristic of copper is completely natural and is often referred to as the “patina” – which referrers to the way copper changes color and turns green as it ages.  This natural process actually preserves the copper and protects it from the outside elements.


Copper Patina Color Chart


Why Copper Turns Green - Copper Patina Color Chart


Over time copper will naturally change colors – transforming from a shiny brown color to darker browns, then blues and finally greens after a number of years.  When exposed to the natural elements such as wind and rain, copper develops this “patina” which actually protects and preserves the metal underneath.


 

Natural Oxidation


Just like rust develops on iron, patina develops on copper when the copper sulphate on the surface interacts with oxygen in the environment.  Importantly, unlike rust which corrodes iron, patina actually protects and preserves the copper underneath.  


 

Copper Care


The patina process of copper is completely natural and one of the big draws for people who like its look.  However, some people prefer the newer look of copper and this can be restored with the help of products and a little “elbow grease.”


Buffing is a big part of the cleaning process.  There are also many commercial products as well as homemade concoctions, including those made with vinegar and lemon juice. You should always start by washing the copper with warm water and gentle soap. Avoid using abrasive cleansers or cloths, as they may scratch the copper.