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Why Copper?
Materials: Copper Gutters

Why is it that copper gutters change color over time and eventually turn green? Maybe it’s because they are envious of the house they are attached to. Or maybe they are feeling sick from a upset stomach. Okay, maybe these humorous quips are really not that funny but it does really make us wonder at the science behind this.


A good demonstration of the oxidation that takes place on a gutter. Eventually the darker color will turn green when the patina effect begins.

This is where we are in luck. In gathering information for another informative piece we are constructing, the discovery to this became apparent. It can be quite fascinating. For instance, the greening effect can take 20 years or more to develop and it protects the metal. Copper also shares a few traits with Gold.

Copper is an elemental metal with a high corrosion resistance. Depending on the environment that copper is in, it will either turn green slower or faster. The closer it is to pollutants like urban air or salt-water, the faster it turns green. It turns green because of the reaction to the elements that form on its surface.

When copper is exposed to the atmosphere, it reacts with carbon dioxide, oxygen, moisture and pollutants. Where moisture and oxygen come into contact with copper, it oxidizes the two elements. This will eventually lead to giving the copper a tarnished tan appearance. After a few years, the tarnish will darken into a brown or black.

The copper starts to green when a patina develops on the copper. The patina can form from varying elements in the environment. The copper initially darkens from contact with oxygen to form copper oxide. When there is contact with carbon dioxide and copper, a copper carbonate forms. When either of these reacts to acidic rain or sulfur, the patina begins to form. The patina acts as a protective layer against farther corrosion.

Remember seeing those diving expeditions in search of a missing ship or boat and we see the green copper pipes among the remains? Because of copper’s ability to resist corrosion, it is employed in many structures. Saltwater is highly corrosive to most metals and even alloys. Because copper develops the green patina, it is better protected against the corrosion and is the metal of choice in many applications.


Maybe the reason that Kraken attacked ships long ago is because they contained precious gold. Now all they mostly contain is copper. Can’t buy the little Kraken very much with just pennies.

Although copper is resistant to corrosion, it produces a highly corrosive runoff. The runoff will stain and even corrode surrounding stone and alloys. When we install copper gutters into aluminum downspouts, we have to make sure there is an insulator or the copper would destroy the aluminum. It is less corrosive to tin, lead and galvanized steel.

There is even a process to speed up the patina process in order to add an antique look to a particular item. To do this, chemicals are used to make the copper react faster. The patina is also sought after by people looking to restore an antique piece where something may have broken off.

Maybe one day, someone’s green gutters will make you green with envy. Although we don’t have any process to speed up the greening effect of gutters, we do indeed install copper gutters. If you are ever interested in seeing how copper gutters look on a house, head over to our houzz page. We have a lot of pictures there and be sure to call us at 845-223-6111 or contact us through our website if you are interested in a quote.

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