The Crucial Reason Navy Sailors Don't Clean Their Grimy Coffee Cups

Boats and kitchens are similar spaces in some ways. Captains and (many) home cooks ideally keep both ship-shape, with their pantries ordered just like Ina Garten and everything in its place. But surely even the most laid-back of kitchen owners would grimace at using the same utensil over and over again without washing it. Yet that's how some higher-ranking members of the United States Navy reportedly roll when it comes to their personal coffee cups. Traditionally, it's an unwritten rule that you don't wash your own mug and you never, ever wash someone else's — particularly if they're a senior member of the crew.

A coffee cup with a blackened interior is a visible symbol of the owner's service and the memories associated with their time aboard. We think that's quite a romantic notion for a group of hardened sailors, but there are even deeper layers to the grimy coffee cup tradition. While there are utensils and crockery shared by everyone on board a ship, individual sailors tend to have their own mugs. In an environment where everything is so regimented — a literal tight ship — washing a coffee cup has sometimes been seen as a break in that rhythm to the point of being unlucky. So, almost by unspoken agreement, it wasn't done. The third reason some sailors don't wash their coffee cups: They claim it tastes better because the mug has been seasoned like a skillet. This common condiment might clean their mugs as well as it does cast iron, but a superstitious or sentimental sailor is unlikely to give it a whirl.

We know how pirates cooked their food back in the day, but the seagoing tradition of drinking grog (watered-down rum) in the U.S. Navy ended in 1914, thanks to an order banning it courtesy of then-Secretary of the Navy Josephus Daniels. The "cup of joe" nickname is said to have originated there, but there's no definitive proof. What we can say is that the American military drinks a lot of coffee. Over 950,000 gallons (that's roughly 7.6 million cups) of the stuff was consumed during the six-week Operation Epic Fury campaign, according to the Joint Chiefs of Staff (via CBS News).

Historically, sailors took their coffee as they do now: black, strong, and in large quantities. Sugar and milk, with their shorter shelf lives, were often ditched, so whatever went into the reused mugs always tasted the same — at least to the sailors who drank it. Luckily for those who continue to stick with this tradition, there's little chance that their dirty coffee cup will make them sick. Dr. Jeffrey Starke, former director of infection control at Texas Children's Hospital, told the Wall Street Journal in 2016 that, "Of all the things people have to worry about, getting sick from an old coffee mug is at the bottom."