I'm interested in a bronze As but noticed this small spot of "something", and I'm wondering if it's the infamous bronze disease. It's the only spot of this green on the coin, and it's very small, so not a huge concern. Is it something that would need attention, and would that be a very involved process?
I would leave it alone (that's just me). But you may want to quarantine it from your other bronze coins to prevent spreading.
That will come right off. If you want the coin and the price is right, buy it. PS It looks as if the coin has been painted to hide its surface. I collect these bronze pieces and most of them have problems. They are ancient!
See if you can remove most of it with a toothpick. Then let the coin sit out exposed to air and keep an eye on it for a few weeks. If it is easily removed, and a greenish power comes back and starts to build up at that spot, then it is bronze disease, and you will need to treat the coin. If the green spot is hard, and nothing comes off when you scratch it with a toothpick, then it is not bronze disease.
I don't know. Keeping coins six feet apart seems excessive. Are coins in a particular collection considered family? I mean, they do live in the same household, right?
I keep all my coins in binders. All the coins in the same binder I let mingle. I keep all my binders at least 6 feet apart from each other. Every now and then I will let the coins in one binder visit with those of a different binder via Zoom. The tricky part is the surgical masks. They tend to fall off. I'm still working on this.
I found something similar (if not the same) on one of my coins I had forgotten about and left sitting in the same batch of distilled water (from a dehumidifier) for months without changing. The stuff is surprisingly hard, and I'm pretty sure its not bronze disease. Bronze disease is supposed to be a powdery substance that brushes/scrapes off easily. This particular coin is still undergoing treatment and I am yet to completely remove it. It almost looks like some kind of algae? Perhaps grew from being in distilled water that wasn't properly distilled? p.s. this image is from under a microscope, the green formation covers an area similar to the coin you posted.
