50080

Why is copper roof brown, not green?

September 16, 2008

We installed a copper roof on our dome home, about 20 years ago. Except on a spot where wall boarders urinated on it, it has not turned green. It has the color of an old penny. Aside from aesthetics, is there any advantage in turning it green?

Cliff Skelton
- Mount Vernon, WA

Probably local climate is too dry and relative humidity is low(under 40% )-in that case formation of natural patina is much longer.Hope it helps and good luck!

Goran Budija
- Zagreb, Croatia

Cliff,
As you know, the Washington State climate is far from dry, so low humidity does not apply here. If my geography is correct, Mount Vernon is close to Similk Beach, so the air should contain an adequate amount of salt. You may want to look up the roofing material specs, or contact the mfg to see if there was protective coating applied to the copper. Taking in consideration of the locale, the roof should have turned a greenish color by now.

Mark Baker
Process Engineer - Syracuse, New York

Mark...I'm not so sure high humidity/ocean proximity will cause green corrsion products on copper.

I know of condomiums right on the beach at Hilton Head Island which have copper clad Mansard roofs, and are at least thirty years old. They are 95% chocolate brown with only a few green streaks.

Jeffrey Holmes, CEF - Spartanburg, SC, USA

The USEPA put a copper roof on a new building a few years back and is less than one block from the Pensacola Bay and less than 1 mile from the Gulf of Mexico. In about one year, the roof turned a nice chocolate brown color except for the areas where they soldered it and got excess flux on the roof.
Most of the roofs at UWF turned a green (built about 1964).
I think that it has more to do with the alloy of copper than anything else.
Check with the original metal MFG.

James Watts
- Navarre, Florida

I remember watching a documentary on copper, copper will turn brown for 20 -100 years. At which case the green color will start to appear as the patina ages and starts to increase the copper.

Their are commercial products that can speed up this process and create a natural patina within minutes.

Memento Mori
- Silver Spring, MD, USA

Hi, Memento. Thanks for that theory; it sounds feasible to me because there is an awful lot of old green stuff out there.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Well, to create a nice Patina-Layer it needs more then just chloride.....what you can try to do is: Make a 10% Ammoniumsulfate-Solution, apply on the your roof (consider pre-treatment) and let it dry on air and observe what will happen.

Dominik Michalek - Mexico City, Mexico

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