Copper Guide Part 1: Copper Alloys—from the Stone Age to Modern Metal Marvels

While many metals have influenced society, not all can claim an entire age in their namesake. From the Sumerians and Chaldeans in Mesopotamia, across Egypt, to present-day Turkey and India, copper has captivated early civilizations dating back to 8000 BC.

The weight and malleable nature of copper was a pivotal discovery because its plasticity was like no other known material. Copper was no ordinary rock—it would not fracture yet yielded to blows and took a different shape.

When the nature of this material (with excellent ductility, high elasticity, and soft edges) was discovered and disseminated by our early ancestors, the Stone Age was over, and the Copper Age was upon civilization.

Let’s explore the fundamentals of copper and its alloys, the pivotal role it plays in modern civilization, and how time itself impacts this intriguing material.

Copper and its Alloys

Of all the metals, only copper and gold possess colors other than gray or silver in their natural forms. Additional elegant colors and tones take hold when copper combines with different elements (early humans were surely captured by the brightly colored ores of copper, malachite, and azurite).

In its commercially pure state, copper is a soft and malleable metal. However, when alloyed with certain other elements and strengthened by thermal and mechanical means, some alloys approach the strength of steel.

Over time, a vast array of alloys with select properties were created for specific environments and manufacturing processes. That’s the beauty of copper, a metal that has been a cultural mainstay for centuries.

Limitless endeavors were devised, and a vernacular all its own surrounds the metal. Names such as Admiralty Metal, Engravers Brass, Naval Brass, Jewelry Bronze, Gilding Metal, and Cartridge Brass were created by industries to describe a particular alloy (established for a specialized purpose).

Resisting (or Embracing) Oxygen’s Attraction

Capturing and maintaining the brightly polished surfaces of copper alloys is no easy task. Methods have been employed over the years to eliminate the powerful drive of the single valence electron of copper to combine with oxygen, the combination that results in the tarnish on the surface of copper alloys.

This is not an issue, however, with the aluminum–bronze alloys. The aluminum bronzes C61000 and C61500 are the most corrosive-resistant of the copper alloys. Still, constant polishing and cleaning are necessary to keep most copper alloys appearing bright and golden. They can be coated and waxed to reduce the frequency of the cleaning regimen.

Exterior roofing and thin copper wall cladding are rarely coated with protective coatings, even if given an artificially induced patina. It is better to allow them to react and change with the environment than to undertake the expensive and somewhat futile endeavor of maintaining their clear coatings.

For example, the de Young museum in Golden Gate Park, San Francisco, has walls and a roof composed of cold rolled copper sheets that are weathering naturally and beautifully.

Copper’s Contemporary Appeal

In contemporary life, copper offers the design community a material for creating timeless beauty. When properly installed and maintained, copper and copper alloys will age gracefully in exterior applications—or they can be frozen with clear protective coatings of lacquers specifically created to protect the copper.

The interiors of churches, synagogues, and mosques are adorned with ornamentation made from copper alloys that have been brightly polished to give a golden reflection, while many of their exteriors are clad in natural aging copper roofing.

Alloy C37700, a forging and machining alloy, was used on the artwork for the Museum of the Bible because it can handle extensive shaping and machining. A CNC Vertical Bridge Mill machine carved each line of text from the solid one-inch brass panels, often taking eight hours or more per piece to complete.

Copper Alloys For The Arts

Bronze has been a stalwart of artists and art collections for centuries. The most common form is cast bronze statuary. Techniques for casting bronze have been perfected by foundries over the years, with by far the most common being lost-wax casting. Usually, a patina is applied to the finished work.

While bronze sculpture is still one of the most common uses of copper in art, the metal lends itself to many other forms. The sheet material can be hammered and shaped and is a favorite metal for chasing and repose work.

Copper’s ability to elongate without cracking and to be softened by annealing makes it well-suited for shaping. Working with sheet copper alloys, artists can create significant and beautiful surfaces by patinating the surface.

The Colorful Potential of Patinas

“Patinas . . . at their best they create a bit of magic or poetry that sings off the form.” —Rungwee Kingdon

Of all the metals, copper and copper alloys offer the most intriguing, natural, and beautiful color possibilities. The copper salts all possess remarkable and intense colors that we refer to as patinas. The methods by which these patinas develop and the chemical compounds they form are extensive.

A Modern Solution: Artificial Green Patinas

With the quality of air today, copper will take a significantly longer time to develop the characteristic green patina of old. Deep green natural patinas, which used to take a decade or so to develop, now will take close to a century or more.

Because of this designers have sought to accelerate the process by utilizing prepatinated material to capture the color tones from the beginning. The process does not use paints or dyes but the actual chemical process that nature would create over years of exposure.

Is Copper Sustainable? Environmental Concerns and Opportunities

Sustainability involves striking a balance, an equilibrium in which the activities involved in producing and using a metal arrives at a workable and sustainable accord with the future.

This accord must consider the impact on the environment, the people working with the material, and the future generations affected. The continued enlightenment of the industry (to look beyond today and into the future) plays a relevant role in sustainability.

There is no question that mining practices in the last century have negatively impacted the environment. Thankfully, changes in thinking are occurring in many of the largest mining firms. Shortsightedness is being replaced with long term responsibility.

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Exploring Metal’s Role in Sustainable Architecture

Today mining reclamation programs are in place to remove, filter, and neutralize mining water and to release clean water back into the environment. Meanwhile, copper is extracted from the water via an iron filtering system. This process of dewatering tailing ponds and flooded sites while recovering copper is in place at many of the largest mining operations throughout the world.

This is just one example of the many improvements occurring across the industry. Modern innovation in sustainable practices will propel copper’s impressive legacy as an intriguing and valuable metal into the next century.

READ MORE: The Finishes, Patinas, and Textures of Copper

In our next installment of this series, we’ll explore the process of applying finishes, evoking a rainbow of patinas, and shaping texture into copper and copper alloys.

Read Part 2 in our series: The Finishes, Patinas, and Textures of Copper.