Steel wool? Abandon all hope, ye who enter. That will leave micro-scratches visible under a magnifying glass, instantly cratering any collector value. Same goes for metal polish, sandpaper, or your neighbor’s power sander. Also: never use white vinegar alone. That stuff is like acid for copper. I once left a penny in vinegar overnight as a science experiment, and the next morning, it looked like a zombie had chewed on it and then died of shame. The copper was literally green and flaking off.
And here’s a surprising fact that will blow your mind: Old pennies that look black and crusty can be incredibly valuable. In 2026, a 1943 copper penny (yes, copper, not steel—a mint error) sold for over $300,000. If someone had “cleaned” that coin with a wire brush back in the 1950s, it would be worth a fraction of that. So before you start scrubbing, ask yourself: “Is this penny 80 years old and do I have any idea what I’m doing?” If the answer to both is “no,” put down the ketchup and step away.
