Patina (/ˈpætɨnə/ or /pəˈtiːnə/) is a tarnish that forms on the surface of copper, bronze and similar metals (produced by oxidation or other chemical processes); stone;[1] a sheen on wooden furniture produced by age, wear, and polishing; or any such acquired change of a surface through age and exposure.

I often receive questions from my Miami, Florida clients about the patina that forms on copper roofs. As with all copper, the patina forms over time and adds a greenish tarnish to the copper. This is due to the oxidization of the metal as a result of the elements interacting with the metal. This produces a coating of varying compounds such as copper chlorides, sulfides, sulfates and carbonates.

A solid patina layer on copper roofing takes many years to develop, but begins within the first few days after the copper is exposed to the elements. Typically, a copper roof that has a natural patina on it will last longer than one that has been stripped of the patina. This is due to the extra layers the patina adds to the copper which provides protection against erosion. Structures in damp coastal/marine environments like Miami, Florida will weather and develop patina layers faster than ones in dry inland areas, although there are ways to speed up the process.

Speeding up Nature

A patina is formed naturally and in order to speed up the process chemicals are needed to change the rate at which the copper roofing forms this layer. It is difficult to speed up nature yet have the results still look natural.

Ammonium Sulfate and chloride salts are used in some applications and need to be painted or sprayed on the roof in order to get good coverage on such a large area. The difficulty with this is that uniformity and color evenness are very difficult to achieve.

There are several chemicals that can be used to speed up your patina and it is always best to consult with an expert before applying anything to your copper roof.

Green be Gone?

Some of my Miami clients have disliked the look of the copper patina and wished it to be removed, I must say that if you do not like the look of the patina it is best to go with another material. There are many roofing materials that share the color and look of copper, but do not get the typical “green” patina.

Often the patina does not form evenly and the process needs to be restarted in those areas. This process can be viewed here.

As with all things, the copper patina is a matter of preference. Not everyone likes the rustic look of the patina and although it does add years to the longevity of the copper, it is simply not aesthetically pleasing to all people. This in mind, Istueta Roofing gives clients the option of many different roofing materials that will best suit the preferences of each individual to ensure that every Istueta client is a happy one.

Thanks for reading,

Frank Istueta