Over the years, the copper mug developed a life of its own, inspiring a fanclub of fervent supporters, who claim that the mug not only makes the drink look better but also makes it taste better. So, does it? We looked to an actual scientist to find out. Enter University of California, Santa Barbara, professor Matthew R. Begley, an expert in solid mechanics.
Here, Dr. Begley’s responses to the three most common copper mug claims.
Claim #1: “Copper mugs keep drinks colder.”
According to Dr. Begley, copper mugs do not keep drinks colder, longer. In fact, it’s exactly the opposite. “They may feel colder but that’s only an illusion,” Dr. Begley says. “Copper mugs actually absorb heat from the room faster than a glass.” Copper is an excellent thermal conductor, meaning it transfers heat from hot sources (like the room or your hand) to cold sources (like your drink) very efficiently.
For those of you who are already a couple of Moscow Mules in, Dr. Begley simplifies it even further: “A big question in grade school science is ‘Why do metals feel colder than wood?’ If you were to pick up a piece of metal and a piece of wood—both sitting at room temperature—you might feel like the metal was colder. The reason for that is the heat from your fingertips gets conducted into the metal.” It’s the same temperature as the wood, but our nerve endings are pulling a con job on our brains.
Claim #2: “Copper adds to the taste of a drink.”
You’ll often hear it described as a “tinny” quality—some sort of metallic essence in a Moscow Mule attributed to the copper mug. Dr. Begley’s response: “Taste is in the eye of the beholder.”
“My intuition is that if you were to give people a blind taste test on this matter—copper mug versus glass—they would turn out the way they usually do, which is blind,” he says. This may be a situation in which our hands, eyes and mouth are conspiring against us, manipulating our brains into sending a certain message. The look and feel of copper lead us to expect a coppery flavor, which our brains politely deliver.
Copper does have one quality, though, that could potentially change the flavor of a drink: It oxidizes, meaning it undergoes a chemical change when exposed to air and humidity. In the wine world, a controversial myth says that if you drop a pre-1982 copper penny (they’re now made of zinc) into a wine suffering from reduction—a lack of oxygen that can sometimes lead to a sulfurous, rotten egg aroma—the copper’s oxidative qualities will battle against those aromas and return wine to its naturally seductive nose.
Could such an oxidative quality make a difference in a Moscow Mule? Dr. Begley admits that this theory might have some traction. Because copper is oxidative, the metal will change the aroma of the drink, which is very much tied to our perception of taste. So, you could conclude that copper does have a tiny effect in the overall Moscow Mule sensory experience—but Dr. Begley reiterates that he does not believe the results would be all that noticeable in an observable lab setting.
Claim #3: “Copper is dangerous and nickel-lined mugs are much safer.”
More and more, Moscow Mule mugs are being crafted with nickel linings, which are supposedly safer for drinkers than 100-percent copper mugs. Dr. Begley’s take is that, unless you have a “bizarrely acidic” cocktail, the copper won’t leach into your drink. And even if it did, you’d have to drink out of that copper every day for years in order to significantly affect your copper intake.
But even if you do subscribe to the “better safe than sorry” approach, Dr. Begley explains that “nickel is no better.” In fact, nickel is currently being eliminated from biomedical implants due to long-term toxicity concerns. That said, Dr. Begley concluded that neither metal poses any significant risk when it comes to drinking vessels. Perhaps this nickel-lined trend is just “a good PR campaign by the Nickel Consortium,” he jokes. In other words, you’re in no danger of copper or nickel poisoning due to your love of Moscow Mules.
After speaking with an actual scientist, here’s what can we confidently say about the trendy vessel: Copper mugs may make a drink seem more appealing, but they don’t actually change its physical makeup.
However, our investigation did inspire a deeper philosophical question: If your brain doesn’t know any better, does it really matter? Are you the type who would take the red pill and unplug from the Matrix, or do you prefer the familiar, copper-tinged charm of the blue pill?
As for Dr. Begley, he admits that he’s not much of a copper mug man himself. He’d rather go for a good Sazerac—no trumped up glassware required.
Jason Booth is a sommelier and the creator of the “Wine for Sophisticated Homies” podcast. When he’s not selling wine and cocktails to rich hipsters, he’s telling bad jokes at late-night comedy clubs around Los Angeles. Follow him on Twitter at @WineHomies.