What is a Patina or, Patination?
Patination is the process of changing the appearance of metal - particularly, copper, brass or bronze. A patina develops on these metals as a layer of protection from corrosion.
While it usually refers to a chemical process, a patina can also mean any aging process that causes natural discoloration or fading, including extreme temperature changes.
As you may know, copper metal is usually a reddish/brown colour, bronze is almost identical and brass is a gleaming gold.
Changes to these colours can be achieved by atmospheric oxidation; where the metal is exposed to the elements to promote ageing.
A real-life example of this can be seen on the Statue of Liberty which was originally a reddish/brown colour due to being primarily copper. Through many years of exposure to salt water, wind, rain, snow, temperature changes and other atmospheric conditions the Statue of Liberty is now mostly green, also known as Verdigris.
In a clean, natural environment, it can take up to 30 years to achieve the iconic green "verdigris" patina that copper is known for. Similar results can be achieved through forced/controlled patination in as little as a few days, with deeper and more colourful patinas taking longer.
Forced patination, is a process where one purposefully aims to change the appearance of a metal. Natural products or chemicals are applied to the metals in a controlled environment. Alternatively, we may expose the metal to extreme temperature changes to create a patina. Both of these methods are forced which speeds up the patination process.
Due to these metals creating their own barrier against corrosion, the resulting colours and patterns are always unique and impossible to replicate - In a way, you could say they themselves decide, how the patina will look.
Some of the most colourful patinas can be created using simple household products such as salt or vinegar. Others are much more complex and require multiple processes and many days, weeks or months to achieve.
Because of patina's aesthetically pleasing appearance, copper and copper alloys, including bronze and brass, are often used in architectural projects.