You may have noticed that over time, objects made of copper, brass, bronze, and various other related metals start to turn a different color.
This is most of the time caused by patina, which is a type of tarnish that forms on the surface of such materials.
In simple terms, patina is an aesthetically pleasing transformation that happens to bare metal when exposed to the elements. Much like how a freshly cut apple begins to turn reddish brown, oxidation occurs and produces an aging effect on the metal surface – it’s all chemistry.
Due to the chemical process that happens naturally, patina usually brings out rich colors in antiques, such as copper pots, creating an even more enchanting aesthetic experience.
But What’s the Purpose of a Patina?
And why are we discussing it here in the first place?
Well, the patina finish is not only visually pleasing; it also offers functional protection against corrosion.
The resulting surface coating is so beautiful that it has increased in popularity over the years and has become a trend in interior design. It can be found in hand tools, furniture, jewelry, and various other decorative items.
While the process was all-natural when Italians first used the term “patina” in the 17th century to refer to the green film that’s produced on the surface of copper, it is today used as an antiquing technique to create unique looks and add character to an object.
But remember, it is nearly impossible for imposters to replicate the exact beauty of the patina finish. Trying to produce one artificially is extremely challenging and usually leads to an inconsistent finish, which can be indicative of it being faked.
Is Patina the Same as Rust Formation?
Patina is formed when the metal is subjected to the environment, particularly weathering. In addition, patina can form through polishing, wear, and even age. The most apparent effect is that bronze, copper, or similar metal has altered in its coloring.
However, while patina is created through the process of oxidation and reduction, the result is not damaging to the metal itself. This means unlike rust, which damages the metal, patina is simply a tarnish that coats and protects the surface of the metal.
But because the patina coating is also created by oxidation, it is sometimes called “patina rust,” which protects the surface underneath without causing any harm to the metal itself.
The most common type of patina is found on coins that are made from copper, bronze, and similar materials. Archeologists have found patina-coated coins that date back many centuries.
It is believed that once a metal is covered in patina, it’s protected from the elements, such as being buried in the ground, and it can last for much longer.
Even a thin protective layer of faux patina, when put on metals like a carbon steel blade on a knife, can help prevent future oxidation (or rusting), providing a much longer life for the metal.
Verdigris vs. Patina – What’s the Difference?
While patina can form on the surface of metals (such as copper, bronze, or brass) along with certain types of stones and wooden furniture due to exposure to the elements, verdigris is a distinctive green pigment created when acetic acid reacts to copper.
You may have noticed green pigments on the Statue of Liberty, copper roofs, or structures that are near seawater. It’s because of the thin protective coating formed on the copper that gives it its distinctive emerald color. This type of patina is referred to as verdigris and can take many years to form.
What’s the Difference Between Tarnish and Patina?
Perhaps the most obvious difference between tarnish and patina is that patina is generally desired while tarnish is not. Tarnish tends to dull the appearance of an object, while patina is seen as an enhancement.
Patina creates either green or brown oxidation coatings, usually only seen in bronze and similar alloys after long periods outside. Tarnish, on the other hand, is more of a general term that can happen more quickly.
Tarnish is simply a type of corrosion that occurs on many metals due to the combination of oxidation and sulfur dioxide. When both elements form on the metal, the result is a slight deterioration to the surface, but the most obvious result is the change in color.
Another method by which tarnish is formed is through abrasion. Metal surfaces that are rubbed with some frequency against another surface may form a tarnish in that area.
Can Patina Formation on Metal be Removed or Stopped?
An antique patina finish is becoming one of the most desirable textures in this modern era. If you want to get an aged, distinctive look on your copper sinks, bathtubs, or pots, a patina is a way to go. The beautiful thing about patina is that it can be easily reversed if necessary.
This means you can remove patinas, if needed, by using commercial metal rust removers or some household items like vinegar, baking soda, and salt. Light rust, tarnish, and patina can also be removed with scrubbing using steel wool or other rough-textured cleaning tools.
To preserve the luxurious appearance and finish of copper pipes, sinks, taps, door handles, etc., many manufacturers also use a variety of exotic paint finishes and lacquer coatings that helps to stop the chemical reaction and hence the formation of unwanted green patina finish.
The Bottom Line
Based on the above, we can say there is no substantial difference between tarnish and patina because patina is also a form of tarnish. Both are also different from rust, even though they are created in a similar fashion.
Tarnish and patina form through the process of oxidation, which happens due to exposure to oxygen in the air, even in dry conditions. Rust takes that a step further because the presence of moisture is required. It is why metal objects in the desert tend to take far longer to form rust because of the lack of moisture.
Jack Luis is a semi-retired painter who loved painting his clients’ ideas on their walls.
He had worked as a painter for over a decade serving customers in areas such as Charleston, Mount Pleasant, Beaufort, and Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques implemented in his profession. You may read more about him here or get in touch with him here.