Copper has many uses and benefits, and on top of it all, it boasts a gleaming amber surface and a patriotic history. But being owners of copper wares, fully versed in its sensitive surface, we were really concerned with the best way to clean and take care of it.

Equal Parts Ketchup and Salt Make Smudged Copper Shiny.

Kaufmann Mercantile spoke with the erudite Mac Kohler, founder of Brooklyn Copper Cookware, the sole manufacturer of copper cookware in the United States, who explained.

KM: There are many formulas for polishing copper, with concoctions including lemon juice and ketchup as well as commercially available polishes. In your opinion and experience, what is the best way to clean copper?

MK: People misunderstand the patina on copper as damage or corrosion, but in fact it is simply the settling of molecules to a more stable order. The Statue of Liberty was initially sprayed with a vinegar solution in order for it to obtain its verdigris (the green pigment). Verdigris actually protects copper—once verdigris sets in, the copper will never corrode.

Natural patinas take years to build up and some chefs have wares that are envy-inducing.

The polishing process actually stirs up the molecules to a state of chaos. The sheen is derived from the prisms of the molecules.

My go-to recipe for polishing copper is equal parts kosher salt and ketchup. Squeeze out a big glob of ketchup and add salt in equal measure. Spread the solution on the copperware and work it with a soft cotton or hemp cloth—not polyester or synthetics, as that will scratch the surface. Buff it out with another natural soft cloth. If you have dark spots on your copper, it is likely a carbon stain from cooking something starchy, like pasta, The water has been taken out of the carbohydrates, creating just carbon, which is black. Carbon and copper bond easily and these spots require a stronger commercial solution. If they don’t come off, they need to be mechanically buffed, essentially breaking off the carbon on the copper surface. I’ve heard of people using a shoe buffer or an orbital sander with a buffing attachment.

Apply. Rub. Buff. Clean.

KM: While we’re talking about it, I was recently gifted a pair of vintage Moscow Mule mugs with the original Cock and Bull restaurant imprint from the 1940s. I’m so excited to use them but I notice they are no longer lined with anything. For example, all Brooklyn Copper Cookware is lined with tin. How important are the linings in copper cookware and is it dangerous if I drink out of my mugs in their current state?  

MK: Copper corrodes when exposed to acid, therefore copper cookware is always lined. You would have to ingest an exorbitant amount of copper for it to be dangerous, but it is better to play it safe and get your mugs relined. However, there is an exception when sugar is involved. The sugar from the ginger beer and simply syrup in a Moscow Mule will impede the copper from leaching into the drink. A good way to test the lining on your mugs or any other cookware is to apply a bit of tomato paste to the section of lining that you are concerned about. If it turns green in the morning, you know that the lining has been breached and your cookware will need to be relined.