Copper Guide Part 3: Dirty Penny™ — Zahner’s Premium Iridescent Copper Patina Surface

Dirty Penny Characteristics and Applications

Well suited for exterior and interior surfaces, Dirty Penny is applied to copper or alloys of copper with high copper content. Creating this patina is similar to creating a red patina and is most often used for copper alloy tabletops, ceilings, and wall panels.

The rich array of colors that emerge from the reddish brown surface (a positive consequence of the cuprous oxide) range from orange to yellow, and even darker hues of purple. These tones are all mottled together and initially have a slight iridescence.

This light interference is possible because the finish is applied unevenly. The glow of the copper shines through at varying degrees. However, the level of iridescence does not remain constant if left untreated. It will eventually darken out in exterior projects as the tonal refraction fades with thickening oxides.

The longer the exposure time to the atmosphere, the greater the bonds between the base metal and the oxide. You can see this phenomenon at 15 Renwick in New York City. At the three-year point, the Dirty Penny finish maintains its clouded contrast. However, the iridescence becomes slightly muted.

Dirty Penny In Zahner Projects

Well-received after its first debut at the University of Wyoming, Dirty Penny now appears on several significant architectural projects. Continuing his legacy in the application of Dirty Penny, Antoine Predock chose this finish for the facade of The Robert Hoag Rawlings Public Library in Pueblo, Colorado.

Collaborating with Zahner on the interior and exterior copper metalwork, the darkened Dirty Penny evokes the Colorado landscape. The library’s exterior blends into the background marvelously.

Related Project

Pueblo Library

Built on the site of the original library, the design by Predock rises five stories to allow view of surrounding mountains and the Arkansas Valley. The building incorporates portions of the existing library and spans across Bates Lane to additional property to the South.

The recently renovated Festival of Arts in Laguna Beach is also clad in the Dirty Penny finish. Unlike a coating of paint or anodization, which will begin to deteriorate, this custom patina will strengthen as the surface oxidizes.

Keen on the words of philosopher Lucius Seneca, “All art is but an imitation of nature,” the architects sought an aged and natural appearance for the perforated copper wall. As a finish, Dirty Penny became the obvious choice.

More Examples of Dirty Penny in Zahner Projects

• Livermore Outlets in San Francisco
• Waipolu Gallery
• John Olver Transit Center

When preparing the commercially pure copper surface for Dirty Penny, Zahner manufacturers get the surface impeccably clean. It must be free of all grease, oil, fingerprints, moisture, and other organic substances.

It also needs to be clean of all oxides. Copper alloys react rapidly with their surroundings, and any oxidation on the surface can render the alloy unreactive. For patinas to be effective, the surface must want to react with the chemistry of the new localized environment.

When working with patinas, exercise caution. The chemicals used in statuary finishes often contain mild acids or strong bases that can be hazardous to a person’s health and the environment. It is critical to work with companies that have established environmental procedures and follow safety protocols.

Keeping in step with Zahner’s sustainability mission, all of our metal patinas are developed in the company’s EPA-certified facility. Practicing clean operations at this award-winning facility ensures safe water waste disposal, preserving the integrity of the community water supply.