Copper and that oh-so-elusive patina

It's remarkably common to hear people ask about copper roof options and then at once ask if “it will go green.” The answer is yes - eventually.
When a new copper roof is first exposed to the elements, it usually has the appearance of a new penny – plus a few hand and foot prints! However, being a natural metal, copper will react to its environment. During the first few months of exposure, it will begin to darken, taking on a dirty gray-brown look that it will keep for a long time to come.

Copper goes green and turquoise after prolonged exposure to moisture. Without accelerating the process, it can take 20 years or more in dry climates for this “patina” to develop.

What is popular for people coveting that old copper roof appearance are artificial aging solutions for copper. These are concoctions of mild acids and other chemicals that dramatically age the copper in a short time – usually a day or two once applied. They can be applied before or after a copper roof is installed, and depending on the skill and experience of the applicator, they can immediately replicate the appearance of a copper roof with decades and decades of exposure.

Regardless, there’s nothing like the look of a real copper roof, and I’ve discovered that artificially aging copper roofs is as much art as science – and like any successful piece of art remarkably satisfying for all involved.

Check out our photos of natural aging ( the curved roof panels) and artificial aging (the shingles). Both of these were about two years old when the photos were taken. Could you tell if you weren’t told which was which?

More questions about copper and other metal roof materials? Download from our website a free copy of my booklet, “What Every Homeowner Needs to Know about Roof Replacement.