Copper Q&A with Thompson
Mar. 29, 2016 Product News

Copper has been used by humans for thousands of years. How much do you know about copper sinks from Thompson?

What are our sinks made from?
Thompson copper sinks are made from commercially pure copper (99.9% copper). While trace amounts of oxygen and phosphorous are present in the remaining 1/10th of a percent, these elements don’t have any effect on strength or its corrosion resistance.

Are our sinks hand-hammered?
Masterful, meticulous, deliberate—these three words describe Thompson coppersmiths. Each maker is a master craftsman in Santa Clara del Cobre, Mexico, a historic coppersmithing region. And, each copper vessel is hand-hammered, creating a unique product that celebrates the area’s legacy, expertise and artistry. Our coppersmiths dedicate hours, days and sometimes weeks to create one-of-a-kind vessels and finishes. Each stroke of our craftsman’s hammer yields a unique piece of art guaranteeing no two products are identical. The hammering process varies depending on the vessel. For example, the Lucca farmhouse sink requires approximately 15,000 strokes in order to attain the final appearance. Read more Thompson’ process by walking through the creation of the Black Copper Alder bath sink.

Where does a copper sink get its strength?
Copper is about as strong as the steel that is used for automotive sheet metal. Like automotive sheet metal, when copper is formed, it gets stiffer and stronger making it harder and more wear-resistant. Copper sinks get their strength from their shape and the thickness of the metal. While our sinks are made from copper that is only 0.060 inches thick, our sinks are drawn to form smooth, rounded corners that make cleaning easy.

Also, because the sink is box-like in shape, it is very rigid, resisting bending and flexing in service.  While our sinks are hot-formed to achieve their general shape the forming temperature is not hot enough to soften the copper. Further, our sinks are hammered after forming, and hammering cold-forms the copper, hardening its surface making it damage-resistant in the same manner as cold rolling does on sinks made from cold rolled copper. One benefit of hammering to harden the copper is that cold rolled copper softens significantly when it is welded, so weld lines on a welded sink will be much softer than seamless hammered sinks.

Is copper safe to use in sinks?
One of the benefits of copper sinks is that copper is a biocide for microbes and bacteria.  Copper alloys are the only solid surfaces that are registered with the U.S. Environmental Protection Agency as antimicrobial.

How should I care for my sink?
Copper sinks grow in beauty with age, maintaining their distinct finish or developing a rich patina over time. It’s what makes each Thompson sink unique. Nurturing copper’s natural beauty is low maintenance, and with care, sinks can last for generations. Find out more here.

Will my sink turn green?
Copper does not turn green in normal household environments, although soaps can contain mild acids and salts that may create an oxide that is other than brown. While the Statue of Liberty skin is pure copper just like our sinks, it is constantly exposed to ocean salt spray which contains chloride salts, resulting in a green-blue patina of copper chloride rather than the medium-brown copper oxide that is formed on the surface of a penny. Normal copper oxide colors develop from deep red at the first stages of oxidation to reddish brown as the oxide layer builds up to old-penny brown when the oxide layer is fully formed. Occasional exposure to household bleach, soap and similar cleaning agents will not cause copper to turn green provided it is not allowed to remain on the surface too long, and if unwanted discoloration occurs, it is normally easy to remove with finger nails or a nylon scraper.