There are at least two schools of thought on the origins of this habit. One is that your coffee tastes richer from the coffee coated inside. We have proof that the other comes from military tradition.
Of his amusing story about ‘Navy Coffee’ on the Naval Historical Foundation site, one man explains how he discovered “old coffee in a cup signifies seniority and stature in the military, particularly on deployment.” He makes it clear that “You may not be able to embrace your loved ones while you are gone, but at least you can still taste the same coffee you drank the day you left.”
You can read more on this here.
If you don’t think it’s gross and you’re willing to give it a shot, here are two tips, so you do it right.
First, don’t share your coffee mug. “It’s safe to refill your dirty cup as long as you’re not sharing it with others", according to infectious disease expert Jeffrey Starke.
Second, it’s not advisable to drink from uncleaned mugs if you mix sugar or cream in your coffee. “If you leave cream or sugar in your mug over the weekend, that can certainly cause mold to grow,” says Starke, a pediatrics professor at Baylor College of Medicine.
Is your coffee mug seasoned? Share your story of your many ringed cup with us and post a pic!