In matter of color, blue and green are almost similar. That's the case of the Turquoise stone. While a majority consider natural turquoise blue, many others see the same stone as green . I think the reverse of your coin reads Nicopolitan in Greek. The exergue should tell us in which city or region this coin was struck. Personally, I noticed this blue patina only on many of my coins from Amisos Pontus.
Perhaps some members may wish to view some examples of bronze disease on the internet. @Nicholas Molinari argue with the CONSERVATION SPECIALISTS. As I wrote, it's all just corrosion to me. But what do I know?
Yes, very true. That's the principle reason many people cannot grade either. They don't distinguish shades of color well. It's all a personal thing - just like corrosion/patina/oxidation.
I know I'm not the brightest student in the class, especially chemistry, but it has been my understanding that bronze disease is a surface problem that can be corrected with the proper cure if caught in time before it destroys the surface of the coin. But, I can get my dunce cap and sit in the corner if this is not correct.
Bing, that is basically correct, though it can penetrate deep into a coin while leaving an outer shell of patina mostly intact. It can be treated effectively in most cases with sodium sesquicarbonate solution. I think Insider was just using the term loosely. For clarification, bronze disease, as opposed to other reactions, can spread very fast if not treated or if the conditions which prompted it are not alleviated. I don't know what chemical reaction caused the blue patina on the OP's coin, but it isn't bronze disease, properly speaking (unless a BD outbreak was covered up with a false patina). "Active corrosion" is more or less a euphemism for "bronze disease" in ancient terminology, so far as I understand.
OK, I understand (I think). BUT, if there is an intact outer shell of patina, how would the BD penetrate underneath? Again, just assume I'm the kid who rides the short bus.
I believe @Kentucky posted a link a while back to an excellent research paper about bronze disease and how to conserve ancients. I think it appeared in a thread "corrosion or patina" - something like that. I'm too chilled-out to go find it at the moment. My apologies.
The shell wouldn't be entirely intact in those cases, but I've seen some where it is nearly complete. It only takes a small breach in the shell, often through over zealous cleaning, to attract BD.
I see you know about conservation. I like your comments in post #26 and sorry to confuse the issue by using (the equivalent of) "rust" in my comments.
No problem. Telling someone his coin has BD is like a doctor saying you have aggressive cancer, and I'd hate to see the OP treat a coin that doesn't need it, which can be very harmful.
I also fall into the "not a chemist" category, or "not a metallurgist" either, for that matter. However, could the bluish patina be related to some impurity present in the metallic composition?
here's some BD. green and powder like flake, eats the coin, will rub off. green and other colors when hard is patina, will not rub off. OP coin has that hard green crust, will not rub off, real or not it will not rub off and isn't BD. just my opinion.
I think the statue has crabs and that is blue ointment... actually, it is rather decorative, but in order to keep it from consuming the coin, I would give it a quick soak in acetone to dry it out and then dry it with a hair dryer or put it into an oven on low heat for a few minutes before placing it in a flip.
OK and thanks! The distinction ancient collectors make is much clearer now. If it is green powder = BD = product of corrosion. If it is green hard encrustation = patina = product of corrosion. I can live with that. And...I should not heat the OP's coin as it is beautiful as is!
ahaha => dude, you sound like you may be slightly high (I like that about you) nasty green powder = active corrosion wonderful green hard crusties = non-active-awesome ancient patina Cheers, coin-bro ... oh, and I totally agree that it is a very cool OP-coin (sadly, it's just a wee bit above my pay-grade)
