Curious if this patina is artificial or natural. At first glance it seems to be some sort of varnish of some kind? If its natural I probably won't mess with it, but if artificial it's coming off. Thanks!
That's a tough one...the bronze showing at the ear might have been where some wore off during a cleaning, but that will happen with natural patina too (I think)
Because of the bare metal we can see, I would bet that it had an unsightly natural patina that was subjected to an overly harsh cleaning treatment, which has sadly made it worse. Good luck with whatever you decide!
Natural or unnatural, that coin looks quite hideous in its current state. I'd either do something about it (electrolysis, Verdi-Care, long-term soaking in olive oil, shorter-term soaking in white vinegar, etc.) or put it back in the ground and let it go.
I vote ugly natural active green corrosion - natural green patina. Here are a few questions. Why would someone corrode a coin on purpose? Isn't most natural patina a much darker green?
a few years ago a coin I had was painted with green paint that came off when I ran the coin under some water lol pic of coin with green paint
Counterfeiters of ancient cash coins out of China have been known to bury their coins in the ground and pee over them for months and sometimes years to age and essentially corrode them to make them look authentic. Here is a recently-discussed example of a Trade Dollar that some speculate could be fake and had intentional damage inflicted to it to conceal its potentially being counterfeit: https://www.cointalk.com/threads/a-coin-only-its-mother-could-love.372323/. So, there are reasons one would intentionally wish to corrode or otherwise damage a coin. The OP's coin I believe is natural but did not respond well to being in the ground and suffered at the hands of an unskilled attempt at cleaning that did not turn out well.
Fortunately I’m a master of my craft lol I’ll try my magic juice and see if it helps. I don’t think it would be possible to make it look any WORSE now
This coin came from the same lot as the below Maximinus. Both had a similar green blue “substance” over it all. Wonder what happened to both of them
Well, not to be a contrarian, but I think the OP looks pretty good. Sometimes a mottled green patina can give a coin a "camouflage" look that makes it hard to see. I prefer this to stripped. My bet is that it looks better in hand? Just my opinion, but I'd let it be. Along the same lines, here's a sad little, square Trebonianus Gallus sestertius with a mottled green patina. It's ugly, but the colors have grown on me, and the central devices aren't too bad. I have no plans on trying to improve it:
Whatever it is, I would not want it in my collection because I think that is active corrosion that will only get worse. This is one of the reasons why I have generally stayed away from ancient copper and bronze coins that had green corrosion on them, especially the bright green stuff.
You are confusing corrosion with bronze disease. Bronze disease will get worse and eventually destroy the coin if not treated. Corrosion, like that on the OP, is stable and won't get any worse once the coin is out of the ground.
I am not confused at all. I would not touch that coin. I guess ancient coins are different from U.S. coins. They are immune, according to you, once they are out of the ground. I place no trust in that concept at all.
Yes, but copper has been corroding for far longer that ancient coins have existed. Copper is copper and it corrodes. The concept is ageless.
It looks like honest original patina to me. And like others have stated, someone tried to clean the obverse. Sometimes this thick green patina can be, well, thick and hide details and fill in cracks over the original metal surface. For example, it originally might not have shown much detail of Gordian's laurel wreath and ear, but with patina removed you can see that there really is minimal wear underneath. The reverse appears mostly untouched... Maybe that's what the obverse looked like to begin with? Who knows, but the damage is done. The coin isn't entirely corroded though I see that it could've been on lower left and right of obverse and top of reverse, based on the muddled legends in that area. I personally think it could benefit from some type of work like you do. You have developed some great knowledge and have shown the appropriate level of constraint when you get to where you want to go with cleaning. I say have at it. It's too bad about the obverse cuz the reverse is pretty acceptable in my eyes. Here's a Hadrian that has a similar green patina with a few corrosion spots on reverse...
When I first started collecting ancient bronze coins, I found this site from Calgary Coins to be very helpful - I still refer to it: https://www.calgarycoin.com/reference/grading/patina.htm There is a lot of information on the web about patina, some of it probably wrong, but this is a good place to start. Here is a green Gordian III sestertius that resembles the OP - green but with some brassy highlights on the inscriptions and devices. The cleaning done on this one (not by me) was pretty successful, I think. It doesn't look stripped and it is easy to see (and photograph).
Very interesting post with varied opinions on, to clean or not to clean that is the question! Thanks everyone.