Mineral oil SHOULD contain only hydrocarbons...@BadThad disagrees and I'm not so cocky as to totally disregard him. Even so, it would evaporate over time and would leave the surface looking as before, which would be dull, which is the reason the oil was used in the first place. @BadThad is 100% correct about the olive oil. In addition to being a mixture of acids (weak, but acids nonetheless) the unsaturation could oxidize and crosslink to form a plastic coating or film...for example, if you mix a color pigment with linseed oil, you get a paint like was used on paintings hundreds of years ago.
This thread would be on fire if I posted all the "forbidden stuff " (such as in the M's: mineral oil, mineral spirits, ?, and ?) we use on coins around here! Best to get some junk coins and experiment for yourself.
Oh yes it does, I've detected those elements at trace levels in every oil I've run on our EDXRF. The lowest levels are in white oil, which is highly refined and purified, but there are still traces. The only "clean" oil I've seen is the analytical diluent stuff and that's by COA.....but since we use it as a diluent, I cannot find anything in it since it's part of the bkg.
I finally took some scans of the coin after I gave them a soak. the first two are what it looks like now and the last 2 are before and for comparison.
I know @BadThad disagreed with me about using oil (of any kind) on coins, but if you used VerdiCare on that coin, it would leave a coating that gives some "shine" to the coin while protecting it.
The first thing I would try is an acetone soak (also called nail polish remover). It has absolutely no effect on the coin itself and it might remove whatever is on the coin. I use it whenever a coin is in a flip that is not inert and leaves a residue on the coin or to remove the stickum if tape comes in contact with a coin. It doesn't remove toning and neither NGC or PCGS don't body bag a coin that's been treated with it.
Yes! This was the first step. He did olive oil and acetone. Hopefully all the conservation specialists here will see that is a very slow and not very effective treatment. I'll bet that NCS (or any coin doctor) would have had this coin finished and off to grading in less than ten minutes. On a bet, I could have fixed it in under a minute in a coin show bathroom, stuck it back in a 2X2, and sold it that day and I'm not a coin doctor - I just read a lot. IMO, the OP is going slowly, probably learning some things, and hopefully we'll see the results when he's done.
Sorry this was so long in coming, after trying various methods on similar coins I finally think I got my coin to look a little bit better. I will start with the start of the coin before I tried anything then the second and final photo's. Let me know what you think.
That's about what I expected it to look like. If you are satisfied, all is good. I wonder though, if you added a single cent to it's market value, if that was what you were aiming for.
I am happy with the results. I can see more of the details without the green. And as someone pointed out it is still a corroded coin. I had not really given much thought as to selling this and how much more money if any it would bring. But if it does and I decided to sell it then that would be great.