The peacock of metals: copper

It may be the bright shiny look right after installation, or one of the shades of brown that show up in the next few years, or the bluish-green look that evolves a decade or two later, but at some point during its aging process, a copper roofing material will hit on a color that appeals to everyone.
Copper has a rich architectural history — for more than 100 years, copper has served as roofing or as an accent on bay windows, dormers, domes, spires, or gutters. Its history can be linked to its durability and prestigious appearance. “For some, they love how it looks and for some it’s a status thing,” says Joe Chiovare of Custom-Bilt Metals. “I remember Donald Trump pointing out his favorite building in an episode of The Apprentice. They were flying over a building he owns and he said it was his favorite because it had a copper roof.”
That’s quite a testimonial and it’s deserved. Copper is the only roofing material ever specified by renowned architect Frank Lloyd Wright.
For years, copper was reserved for institutional applications — buildings that will serve the public or a congregation for generations. As early as the 1700s, those charged with making roofing material decisions for university buildings, government buildings, and churches had the foresight to choose copper. The life-cycle cost of copper can make it a bargain on institutional applications. The copper roof on Old Christ Church in Philadelphia was installed in 1742 and is believed to be the oldest copper roof in the United States. For many such structures, the copper roof is the most architecturally distinguishable feature, and it’s all about the look.
Copper is truly the metal of many colors. It’s easy to see just looking at a handful of pennies: new pennies are shiny and bright, while the older ones may be brown or even green. (Do you think pennies are Trump’s favorite coin because they’re made of copper?)
“People with money think copper is muy bitchin’ and they’re putting in on second homes, $2 million and $3 million homes,” says Drew Popson of Custom-Bilt. “It’s more bragging rights than anything else … you know, ‘I got a copper roof.’”
Customers who know copper as a roofing material accept and appreciate the graceful maturation. For some, that aging process is the attraction. Others want a specific shade of copper and want it now and forever, with no changes.

Patinating, pre-patinating
For those who lack the patience to wait for copper to reach the patina green it’s famous for, there are methods to speed up the process — or at least present the illusion the process has been accelerated.
According to the Copper Development Association, various chemical solutions can be applied to achieve a statuary finish (ammonium sulfide base or potassium sulfide base) or a green patina finish (ammonium sulfate base, ammonium chloride base, or cuprous chloride/hydrochloric acid base). The CDA also warns that results from these field patination applications can be influenced by humidity, temperature, time, and surface preparation.
Some manufacturers are offering pre-patinated copper as a part of their product line.
Revere Copper offers EverGreen pre-patinated architectural copper sheets. Dave Hunt, manager of architectural services at Revere Copper, says the pre-patinating process takes more than 50 days. In simplest terms, copper sheets are cleaned and treated with a proprietary solution and placed in an environmental chamber, where humidity, temperature, and airflow are all controlled. During the ensuing time period of 48 to 72 hours, the chemical reaction between the copper and the solution forms crystals on the sheets. Those sheets are removed and left undisturbed under ambient conditions for seven weeks, as the crystals grow and harden and the sheets develop a yellow-green cast.
“That’s how we ship them, as airtight as possible,” Hunt says. “When they arrive on the jobsite, the crystals have converted from a copper-chloride compound to a copper-chloride-hydroxide compound and have achieved the color that Mother Nature would have taken 15-20 years to achieve in Key West.”
Outokumpu Americas has Nordic Green Plus, available in pre-patinated coils. With this pre-patination method various surfaces are achievable, traditional green, and living 1, and living 2 surfaces. Nordic Brown has been developed to give architects another choice. The dark oxidized surface is equivalent to the degree of natural oxidation obtained before the development of a green patina can be observed. The chestnut brown surface may be allowed to remain, or, when a post-patinated surface is required it can provide the basis of the Nordic Green process, without the lengthy wait for natural oxidation.

Patina by painting
Copper demands patience. The aging process doesn’t happen overnight, unless you investigate some options.
The recent paint system technologies have allowed manufacturers to provide customers with painted steel and aluminum roofing to replicate the look of copper — in any number of stages. Some manufacturers offer five or six paint colors that replicate different stages of copper. “With our variety of colors designed to look like the different stages of aging copper, it’s difficult to discern if it’s painted metal or copper,” says Popson.
Copper is softer than steel or aluminum and it requires special care when being handled. Still, steel and aluminum panels coated in a Kynar 500 system must be handled with care as well, to prevent damage to the coating. Those used to working with painted steel and aluminum are able to offer the aesthetic benefit of a particular shade of copper without having to deal with special handling and installation requirements of copper.
“Some of those end users want the permanent look of copper right away, they want a look that will not change, and that works with steel and aluminum,” says Mike Petersen of Petersen Aluminum. “Right now, copper is so expensive, I believe it’s losing market share. Some of those metals, with prices driven by the London Exchange, are at historic prices.”
Despite the fact that aluminum has also risen dramatically in price during the last year, Petersen says the advantage painted steel and aluminum have over copper is a consistent look, which became more consistent with the evolution of the Kynar 500 coatings.
Petersen Aluminum’s market for copper is good in what Petersen calls “urban environments.” It sells in Washington D.C., in the New England states, and in the Chicago area. It’s popular as a flashing material and for a variety of institutional roofing applications.
In 2005, Revere Copper introduced a painted copper product, Patriot Green. The solid copper is mostly, but not completely, coated with a bluish-green coating, creating the authentic look of mottled copper. With environmental exposure, the uncoated areas will form natural patina; then, as the coating fades away, the entire surface will mature.

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