Is Verdigris on Coins Toxic?

If you just found a coin with green crust on it and you’re wondering if it’s dangerous, you’re not alone. That green stuff is called verdigris, and it shows up on a lot of older pennies and copper coins.

The short answer: it’s not deadly, but you shouldn’t eat it. Verdigris can be mildly toxic if ingested, especially in larger amounts. Touching it isn’t usually harmful, but you should wash your hands and keep it away from your mouth, your food, and your kids.

This post breaks down what verdigris is, why it shows up on coins, whether it’s dangerous, and how to deal with it safely.

What Is Verdigris?

Verdigris is a green or bluish buildup that forms when copper reacts with moisture, oxygen, and acids. You’ll see it most often on older coins, especially those made of bronze or copper like Indian Head cents or early Lincoln pennies. It’s not mold, and it’s not always a sign that the coin is ruined, though it can cause damage over time.

This reaction can happen naturally over decades in the ground or inside old albums. It can also show up faster in damp storage conditions or when coins are stored in PVC flips. The surface starts to break down, and copper salts begin to build up, forming the green crust that gets called verdigris.

Some collectors confuse it with corrosion or mistake it for a sign of cleaning, but it’s really just a chemical reaction from exposure to the wrong environment.

Is Verdigris Dangerous to Touch or Breathe In?

For most people, verdigris on a coin isn’t something to panic about. It’s not radioactive, it’s not mold, and you’re not going to get sick from holding a coin with it. That said, verdigris is made up of copper salts, and those can be irritating if they get into your eyes, mouth, or open cuts.

You don’t need gloves to handle a coin with verdigris, but it’s smart to wash your hands afterward. If a kid puts a coin like that in their mouth, the risk isn’t just the verdigris. There’s also the choking hazard, not to mention the general grime that comes with old coins. You don’t know where that penny’s been, and there’s a good chance it’s been in worse places than your kid’s mouth.

In rare cases, if someone is grinding, scraping, or chemically removing verdigris in a poorly ventilated space, it could cause irritation. But for regular collectors just sorting through coins or flipping through an album, the risk is basically zero. Common sense handling goes a long way.

Should You Clean Verdigris Off Your Coins?

If the coin is valuable, probably not. Any attempt to remove verdigris risks damaging the surface underneath. That can destroy original luster, leave visible scratches, or even change the coin’s color. For anything with collector value, leave it alone or consult a professional conservator.

For lower-value coins or ones you don’t want turning green in storage, you can try to stop it from getting worse. Verdigris thrives in humid environments, so dry storage with desiccant packs can help. Some collectors use acetone soaks to remove organics, but that won’t dissolve verdigris. Anything stronger than that, like commercial metal cleaners or acids, is risky and should be used with extreme caution, if at all.

If you decide to experiment on common coins, document the process and be prepared for less-than-perfect results. Once you start scraping or scrubbing, there’s no going back.

How to Store Coins with Verdigris

If you’re not removing the verdigris, the best move is to isolate the affected coin. Keep it away from others so it doesn’t spread contamination. Use a non-PVC flip or an acid-free envelope, and add a silica gel packet nearby to control humidity. Airtight containers help, but even basic dry storage goes a long way.

Final Thoughts

Verdigris isn’t something to panic about, but it’s not something to ignore either. While it’s not highly toxic in small doses, it’s still a form of copper corrosion, and corrosion spreads. Whether you’re a collector, a seller, or just someone who found a green coin in the junk drawer, the smart move is to keep your hands clean, store the coin safely, and avoid letting it come into contact with others.