I'm quite shocked that this happened but if you say that this is cleaned, 10 out of 10 will say so. But if I said I was conserving this coin by putting it in olive oil for about a week or so, would you believe me? This was what it was originally It's a rather scarce coin and thought if I could get rid of the verdigris, it would be better. But not when it looks cleaned. I didn't do anything special to the coin - just took it out from the container that had olive oil and washed it with water. But when I pat it dry - patina just stripped off. Came as a shock to me. It's not the first time I've conserved copper coins - I have some coins that have been in olive oil for more than 1 month and one up to almost a year and I have changed the oil regularly. This one took me as a big surprise - it shouldn't have happened but it CAN happen. I guess the moral of the story is to look at your coins a bit more often if you are conserving. It's a shame, this is one coin that I cannot upgrade easily or even downgrade to start out with.
There are acids in olive oil which do react as pointed out; ever notice that bitter aftertaste with olive oil on your salad? Possibly the ultra-refined olive oil would be better or less reactive oils; baby oil? Too bad, I only remove film and other junk from low end coins like silver dollars if they are gross and unsaleable even as culls.
When I was into metal detecting I read somewere that you should never use Olive Oil as it has acid. You should use motor oil " I cant remember the name " but the one with no added cemilcals. The basic old fashion oil. But then again NEVER CLEAN COINS !
From the wikipedia entry for Olive Oil. Fats and oils in general are the glyceride esters of fatty acids. Remember triglycerides.[TABLE="class: infobox, width: 23"] [/TABLE] [TABLE="class: MsoNormalTable, width: 276"] [TD="bgcolor: transparent, colspan: 2"]Fat composition [/TD] [TD="bgcolor: transparent"] Saturated fats[/TD] [TD="bgcolor: transparent"] Palmitic acid: 7.5–20.0% Stearic acid: 0.5–5.0% Arachidic acid: <0.6% Behenic acid: <0.3% Myristic acid: <0.05% Lignoceric acid: <0.2%[/TD] [TD="bgcolor: transparent"] Unsaturated fats[/TD] [TD="bgcolor: transparent"] yes[/TD] [TD="bgcolor: transparent"] Monounsaturated fats[/TD] [TD="bgcolor: transparent"] Oleic acid: 55.0–83.0% Palmitoleic acid: 0.3–3.5%[/TD] [TD="bgcolor: transparent"] Polyunsaturated fats[/TD] [TD="bgcolor: transparent"] Linoleic acid: 3.5–21.0 % α-Linolenic acid: <1.0%[/TD] [/TABLE] [TABLE="class: infobox, width: 23"] [/TABLE]
This is the part that catches my interest. Verdigris should not come off like that. If it was due to a chemical reaction, it would have been in solution. I have never had an instance of an ancient coin doing this, but a modern coin that had been treated with a darkener wax did, as the oil loosened the waxy base. I wonder if this coin had been cleaned in the past and darkened to hide such area? Just doesn't seem likely otherwise. IMO~Speculative. Jim
The coin might have been boinked prior to your treatment of it and the treatment might have removed the old layer of manipulation.
It's definitely extra virgin olive oil if you are wondering. I don't have the brand handy but it's definitely the case as I only buy extra virgin. Some would debate why clean coins but I would prefer to call it "preserving" as if you let copper coins sit as it is, the verdigris will eat the coin up over time. As some have suspected, it could be the case of artificial patina. I had another coin using the same batch of olive oil and it turned out to be ok. This is another example This turned out to be ok, didn't it? It was full of verdigris on one side as you could tell from the pit marks. Nevertheless, an interesting lesson learned. Least I know that this coin isn't full of verdigris damage which would have happened if I let it sit over many years.
I've experienced something similar, it was a cheaply bought Roman follis, the coin itself looked good on the pictures what I didn't like was the way the surface felt (soft). I put it into olive oil for an hour and after removing and patting the coin, the "patina" came partly off and hidden damage could be seen. The coin had been treated with strong acid, and the patina was eaten away, the coin was tooled and someone tried to hide the damage of a failed cleaning job.
I agree completely. I have never seen olive oil do something like that unless the coin had an artificial patina to begin with. Problem with cleaning coins is many times what is underneath is worst than what you started with.
