Inside the Factory: The Alchemy of Patina

Solid brass is one of our favorite materials to work with, in part because the finish options are so attractively diverse. For example, many of our signature brass finishes—like Natural Brass, Matte Bronze, and True Black—are achieved by adding a rich patina to the fixtures’ parts before they are assembled. Adding the patina in-house is one of the many old-school but character-building finishing processes that are part of the Schoolhouse repertoire.

“Patina can be a messy, finicky process that a lot of people don’t want to deal with,” says Schoolhouse Production Manager Andrew Bohl. “But sending parts to a third party ties up resources and requires downtime for shipping and receiving. As a company that often manages the entire life of the product under one roof, we want to have that extra degree of control in both the finish and flexibility of production.”

The application of patina, a process known as patination, has existed in some form or another for centuries. It was originally created as an aesthetic improvement for bronze sculptures meant to mimic the natural patina that develops on the metal over time. Giorgio Vasari, the Italian painter and pioneer art historian, mentioned patination as early as the mid-16th century. Writing about the bronze sculptures of his era, Vasari says, “Some turn it black with oil, and others with vinegar make it green, and others with varnish give it the color of black so that everyone makes it as he likes best.” 



The application process has changed over the years as scientists have figured out what actually causes these effects, but the goal hasn’t. Patina adds a beautiful depth of character to metals that helps keep them looking good for years to come.

So how exactly does patination work? As it occurs on the fourth floor of our factory, the process appears to be as simple as dipping parts in a series of chemical baths. But what happens on a chemical level at each stage is more complex. 
The parts being patinated come directly from the sandblasting or buffing rooms which causes them to have a thin film of buffing compound or dust. To clean the parts, the “cooks” (our term for people working at the patina station) start by submerging the parts in hot soapy water. Large racks of parts all get washed together for efficiency and to ensure the parts have as similar of a finish as possible. After the hot soapy water, the parts take a quick dip in clean water to remove the soap.

Next, they’re dunked in the “pickle,” a very weak acid which helps to neutralize the pH of the surface of the part. This step doesn’t change the metal at all—it just helps make sure no soapy, alkaline residue follows the parts to the next stage. Once again, they’re rinsed in clean water. 
After these parts have gone through these preparatory steps, they take their most important bath: the patina bath. Patina isn’t like paint or even powder coating because it’s not something that sits on the surface of the metal. It’s something that changes the metal itself.

Brass is an alloy, meaning it is a mixture of multiple metals (in this case those metals are copper and zinc.) The patina solution is composed of multiple chemicals, some of which bond with the copper and create new compounds. The longer the part is left in the solution, the more compounds will build up, and the darker the part will become. 
The parts are usually left in the patina bath for anywhere from a few seconds to several minutes. Once the desired color is achieved—warm gold for Natural Brass, chocolatey brown for Matte Bronze, and a dark gunmetal color for True Black—the parts take one final rinse in clean water before they are dried.

The complete process requires an unseen degree of skill from each of the workers. 
“They use timers for each set of parts, but it’s not as simple as that,” says Assistant Production Manager Jensyn LaDuke. “They have to adjust their timing due to many variables. For example, a cast brass piece will take on patina at a different rate than a spun brass part. At the beginning of the day after engineers have added fresh chemicals to the solution, the patina bath is ‘hot,’ meaning more concentrated, and parts develop patina faster.”


Once the parts are out of the bath, it’s a race to get each part dry as quickly as possible.
“The drying process is especially difficult,” says Jensyn. “They move their hands quickly and use the compressed air to blast out of every crease and joint in the metal so keep it from holding moisture. If they don’t move quickly, the patina will be uneven.”

When the patina process is complete, the parts head to the lacquer station where they are given a clear coating to protect the surface of the brass. The parts need to be lacquered within an hour or two because even exposure to air and light for a short period of time without protection can affect the color. After this step is complete, however, the parts are ready to head downstairs to the second floor, where they will be assembled into your favorite lamps and light fixtures.

In-house patination is something that many lighting companies don’t bother with because it’s difficult to perfect at scale. But commitment to details like this is what sets our brass lighting, clocks, and home decor apart from the rest.

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