What Leads to the Formation of Patina in Copper?
What is copper?
Copper is a reddish brown chemical element closely related to gold and silver. Copper is a malleable metal and thus is used for making coins, utensils, etc. It is also highly conductive in nature and conducts heat and energy equally well. It is also one of the oldest metals to be discovered and utilized by the human race.
What is the reason for copper turning green?
It is due to the oxidation process of copper that it turns green. When left exposed to air and water, it leads to the formation of a thin, green layer on the surface of the metal. This green substance is known as copper carbonate. But unlike iron which gets weakened when rusted, the green patina doesn't affect the quality of the metal. In fact, some people say that the green substance protects the surface of the metal. Oxidation is a slow process and takes time and before turning green the copper may turn dark brown and black. The green material is also called patina.
What is the use of patina?
It may seem useless, but the patina too has some uses. During the past years, the Greek artists used to use this green patina in their artwork. It was called 'verdigris' which means "green of Greece". It was considered to be the brightest green pigment available but due its poor durability it was abandoned by the artists during the late 1800's. Another use of this patina was to date objects. It was popular in the antique trade business where it was thought to preserve the integrity of the object. Patina is also utilized in some functions of the electrical engineering as well.
Common examples of patina
One of the most famous examples of copper patina is the well known Statue of Liberty. Not many people know that this world known landmark is made of copper. It has been known for its light green color which is nothing but patina. This happened when the copper material of which the statue is made reacted with the water and air and oxidized over a span of years. Old cooking pots and firearms also develop patina on their surface as they age. For some people it adds to the character and value of the product. The best part is that it can easily be cleaned with little bit of effort.
How to get rid of the patina?
Keeping copper utensils in direct sunlight will help with the prevention of the formation of the green patina. It is the oxygen which leads to the formation of the green layer and thus preventing the oxygen come in contact with the metal will stop the patina formation. A great way to get rid of the patina is by using a solution of salt and vinegar. After the patina has been cleaned the surface of the item should be wiped off from the surface to avoid water marks.