I am debating about using Verdi-care or maybe mineral oil on this coin. Does it look like it is worth the trouble? Would I see a good improvement in it?
Verdi care would stop the green moss on it. And most likely help remove it. But the surfaces will always be porous
It appears that porosity and environmental damage are very common on these old coppers especially early matron heads. I wonder if the TPGs hold them to a different standard because of this.
Will Verdi-Care get some of the green stuff off ? Yes. Will it get all of it off ? Probably not. Would that be a good improvement ? Only you can say. As far as stopping or preventing future growth of verdigris, Verdi-Care will help with that, but only if you store the coin properly.
IMO the serious damage has already occurred. Ergo I can't see Verdi-Care causing much more. But I'd start off with acetone. And consider olive oil rather than mineral oil.
Couldn't hurt that one much. I would say it is a good candidate to experiment upon. I, over the years, have experimented with various ways to improve damaged coins. After all that I still further ruin about as many as I help. Copper is almost impossible to improve. Always use coins who's value wouldn't be lowered by much if the experiment fails.
That coin will be 200 years old next month and it looks like it. I'm a big fan of Verdi-care, but it is not a magic wand. It will likely enable you to remove the green, but the effected areas will likely be pretty dark.
I had some green coins. I rinsed them in acetone, then xylene. Then soaked them in Verdi-Care for a few hours until the green stuff was able to come off when I poked it with a toothpick. If you use Verdi-Care, follow the directions exactly. I was happy with the results.
I don't use acetone on coppers since it can turn coppers funky colors. Distilled water and Verdi-care is the only thing I have seen improvements. Yes something to consider, most have developed some sort of damage it seems in that time period. When I see a matron head with nice surfaces at a low price, I grab them.
Acetone can affect copper, but you have to help it by using it in bright light and high humidity, and you need to wait a bit for the reaction to develop enough acid to attack the coin. Under normal usage, you'll never approach that condition. Obviously caution for the coin is the highest priority when we contemplate a conservation, but I don't consider this potential reaction to be an impediment. I simply don't allow the conditions for it to exist, which is in harmony with normal workflow anyway.
The light to moderate verdigris will be improved but that thick, heavy verdigris on the reverse is there to stay IMO. Typically, the only way to remove corrosion that thick is with acids. However, acid will really destroy the patina and probably reveal more pitting. Recommend at 24-48 hour soak, then toothpick method (under fluid!), and finally towel method. Let it dry for a week or two, then put it into a 2x2 or ait-tite.
I think people use oils on coins for two reasons; first, with a long soak, the oil can penetrate some of the corrosion on a coin and loosen it up; second, the oil will add a sheen to the coin and improve the appearance.
Olive oil is an ester of some fatty acids. Not saying that these would be destructive, but that is what it is. Mineral oil is simply a hydrocarbon, unlikely to do anything except to add some sheen or gloss to a surface until it evaporates.