Acetone never removes actual patina. It might remove "fake patina", i.e. crud and ectoplasm stuck to the coin, or even certain types of artificial toning. But it will never touch genuine patina.
And if an acetone soak is "adding color", then you're doing it wrong - it means you're leaving dirty acetone on the coin to dry out. Rinse off the dirty acetone with fresh acetone before it dries.
Now for the OP's questions.
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But does that idea really apply to a relatively new coin in circulation? The coin doesn't really have patina, it has dirt. Gray film, sometimes sticky gunk, often just fingerprints and haze from handling. Is it as deeply objectionable to remove that debris prior to sale?
Patina isn't merely "old dirt". Patina is oxidized metal, chemically bonded to the surface of the coin and cannot be removed without a chemical reaction harsh enough to dissolve some of the metal. Patina is, in essence, a form of corrosion, from a chemistry point of view - but it's corrosion that is relatively mild and in some cases even beneficial, so we've learned to like the appearance and prefer to keep it there rather than remove it.
You've listed several symptoms, some of which are "patina", some are not.
"Gray film" - not quite sure what this means, but it sure sounds like patina - a dark grey toning.
"Sticky gunk" is certainly some sort of "goo" that should come off in either water or acetone.
"Fingerprints" - here we have two different factors at play. Fresh fingerprints - for example, you have literally just touched the coin a minute ago - would qualify as "oil" that can be removed with acetone. The oil has not yet had time to react with the metal. An "old fingerprint", where the metal has changed colour because of chemical reaction with the oil, is unfortunately now part of the patina. You can use acetone to wash off the remnants of the fingerprint oil, but the print itself will remain. This should not be removed, as ugly and incriminating as it may appear.
"Haze from handling" - again, not quite sure what this refers to, but it sounds like plain old wear. Which again, is patina, not dirt.
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But if I acetone cleaned a 2009 nickel to a bright gleam, is that also wrong?
On the general topic of "dirty new coins", a 2009 nickel is 15 years old - that's starting to get old enough for "genuine patina" to develop. A 2019 nickel, on the other hand, is not. One then has to wonder how a coin that new ould get so "dirty" in such a short time. The answer is usually "environmental damage" - in other words, aggressive corrosion due to adverse chemical conditions. Tossed in a swimming pool and left there for a month or so, getting buried in acidic soil, even getting tossed into a fire, can all cause severe corrosion to develop even on a brand new coin. We call this "corrosion" rather than "patina", because it's ugly and we don't like it, but it's chemically not all that different to normal patina. Such coins are generally considered "beyond repair" - anything done to remove the corrosion is going to result in a "cleaned coin".
On the subject of disclosure: acetone cleaning need not be disclosed, since it does not chemically react with the coin or the patina. Anything that removes patina/corrosion - acids, electrolysis, silver dip, a brass brush - should be disclosed on sale, especially if such treatment is not otherwise evident in the sale listing.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
Posted 01/27/2024 2:58 pm
