Why does copper change colors with age?
As one of the oldest roofing materials, copper is a non-precious metal known for its durability and versatility. Used in everything from art to appliances to roofing, copper is celebrated for its natural aging process, which slowly develops over time as the metal oxidizes.
Copper ore is mined from all over the world. The US is the second-largest producer of copper, following closely behind Chile. Copper is considered a native metal – meaning it is usable in its original, earth-mined form. However, advancements in refining and strengthening copper mean today’s copper goes through multiple phases before made available for use. Pure copper is orange-red, and darkens when exposed to air.
Once extracted from pit mines, copper goes through a refining process which includes smelting, slag removal, and casting. Because copper occurs naturally, the initial material mined from the earth contains impurities (typically other metals). Smelting is the process through which raw copper becomes metal; the ore is heated to separate it from impurities and inclusions.
Alloys are metal compounds created to enhance certain properties of the primary metal. Copper alloys, for example, have copper as the principal material, combined with metals like zinc or tin. Zinc and copper create brass, while tin and copper create bronze. The addition of other metals to copper changes the way the metal looks and ages.
When fabricated into market-ready products and materials, copper is a rose-tinted, warm metal. It can either have a brushed or polished finish, meaning it either is matte (brushed) or high shine (polished). Even if the product is a copper alloy, it will still have the same tone / tint typical of natural copper.
Changes take place as copper oxidizes – or is exposed to oxygen. Oxidation occurs naturally. Particularly when applied as a roofing or gutter material, copper’s aging process begins with exposure. Though it doesn’t change the strength of the metal itself, the copper will begin to take on a different hue altogether.
Patina is the new finish mature copper takes on. It is a natural aging process that occurs over time. Depending on the compound, copper patina can range from dark sea-green to a light turquoise. The spectrum of color changes is related to the presence of different metals; for example, a darker patina reflects the presence of malachite, azurite and brochantite.
The rate at which patina develops stems from several environmental factors, or what the copper comes in direct contact with. For interior copper pieces, everything from the amount of ventilation to heat from appliances can affect the process. For copper roofing and exterior home accents with direct environmental exposure, the climate, level of precipitation / humidity, and even air pollution can impact the way patina develops.
All in all, copper is a durable, incredibly versatile material, and can be fabricated to suit any home project. Guy Roofing’s in-house metal fabrication shop custom-crafts each copper piece we install, and our coppersmiths can create everything from mailboxes to weathervanes!
For more on our metal shop, click here.