How to Tell Verdigris from Patina on Coins
If you’ve ever pulled a green coin from a roll and thought, “That’s just aging,” you might have been wrong. Not every color shift on copper or bronze is a problem. But some are. Patina is what happens when metal ages well. Verdigris is what happens when it doesn’t.
This isn’t a minor detail. Misreading the surface can lead to trashed value, bad storage decisions, or a coin that keeps rotting in your safe. You don’t need special tools to tell them apart. You just need to know what to look for.
What Is Verdigris?
Verdigris is the green gunk that forms when copper reacts with moisture, oxygen, or certain chemicals. It’s corrosive. It eats into the surface of a coin and keeps going if you don’t stop it. It’s not just color, it’s damage.
You’ll usually see it as bright green crust, blue-green fuzz, or sticky green film. It can show up on copper, bronze, or brass coins, especially if they’ve been stored in PVC flips, humid air, or plastic holders that off-gas.
Verdigris isn’t toning. It’s not a look. It’s a chemical reaction that needs to be removed or neutralized. Left alone, it spreads.
What Is Patina?
Patina is the thin surface layer that forms on metal over time. On coins, it shows up as natural darkening or mellowing of the original color. Brown copper. Warm gold tones. Soft grays. It’s stable, protective, and usually a good sign.
Patina doesn’t flake off. It doesn’t spread. It won’t eat the coin. In fact, collectors often prefer coins with original patina intact because it shows the coin hasn’t been cleaned or messed with.
Where verdigris is active corrosion, patina is passive aging. One destroys the coin. The other tells its story.
How to Tell Verdigris from Patina
The easiest test is visual and textural. Verdigris looks alive. Patina doesn’t.
Verdigris:
- Bright green, blue-green, or turquoise
- Often fuzzy, crusty, or waxy
- Raised above the surface
- Can look wet or sticky
- Shows up in patches or clumps
- May spread over time
Patina:
- Brown, olive, gray, or charcoal
- Smooth and even
- Flat against the metal
- Feels dry, not tacky
- Covers the whole coin or settles into recesses
- Stays stable
If you’re not sure, tilt the coin in the light. Verdigris usually catches light differently. It can glisten or cast a shadow because it’s sitting on top. Patina doesn’t do that.
You can also use a toothpick, gently. Verdigris might flake or smear. Patina won’t budge.
Why It Matters for Value and Storage
Verdigris doesn’t just look bad. It kills value. A coin with active corrosion is a liability, not a collectible. If you’re buying or selling, verdigris drops the price fast. It hits copper coins the hardest, where the damage is most visible.
Even worse, it keeps going in storage. If you throw a coin with verdigris into a 2×2 or a flip and forget about it, you might come back to find the damage worse. Sometimes it even spreads to nearby coins. One green Lincoln can ruin a whole roll.
Patina is different. It protects the surface and shows the coin hasn’t been tampered with. If you strip it off, you risk making the coin look cleaned. That hurts value too, just in a different way.
If you’re unsure what you’re looking at, read What Is Verdigris on Coins? for a closer breakdown. And if you’re already dealing with it, check out How to Store Coins with Verdigris to keep it from getting worse.
Bottom Line
If it’s green and growing, it’s verdigris. If it’s dark and stable, it’s patina. One needs action. The other needs respect. Learn the difference, and your coins will thank you.