FREE COIN GONE

I personally prefer my ancients to be coated with green.. it's a good sign of authenticity and antiquity.. my top favorite would be the Jade Green and cobalt blue verdigris...

 

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Curious: What feature would not meet their approval? The coin (it is Christian, they are not) or the fact that you got it from online contacts? Both are perfectly reasonable objections. The first might be correctable with a coin that is not overtly Christian. The second will just require you to hold on to that desire until you are older and then come back and remind us we should send you a coin.

 

Not sure if I would call the green patina verdigris. Verdigris will spread and eat up the coin, but AFAIK the green patina won't. Perhaps @BadThad can enlighten us on that.

 

We have a terminology difference here. Verdigris is what we get on the surfaces of copper that protects it from the elements. There is a fine difference between it and bronze disease which is destructive.
https://en.wikipedia.org/wiki/Bronze_disease particularly under Description

 

Not sure if I totally agree with the wikipedia article, especially when the same article recommends (and I quote):
"Internal treatment[edit]
If chloride ions have penetrated beyond the surface more rigorous treatment is required.
This typically involves soaking in acetone to displace any water in the specimen. Then soaking in a benzotriazole (BTA)–ethanol solution to chelate the copper and make it unreactive. Pits and holes may be filled with zinc powder which is then painted over with shellac coloured to look like the specimen."

 

The proper treatment for the Statue of Liberty or a roof will be coarser than allowable for a coin. We see this on million dollar paintings that are cleaned, repaired and overpainted as part of normal conservation. A million dollar coin with filler putty and painted surface stop being valuable very quickly.

 

I agree with you, that is why I would like to see what @BadThad has to say about the matter.

 

Verdigris is ANY type of copper corrosion. I hate the term "bronze disease", it's not a disease, it's copper corrosion and, therefore, verdigris. The reason the term BD even exists is due to ignorance by the non-scientific populace. Verdigris and BD are one in the same.

Verdigris is a very complicated mixture often dominated in composition by the anionic element most prevalent in the environment it was exposed to (i.e. chloride, sulfate, acetate, etc). Also, time, temperature, pressure and other external influences alter the composition - as we see with ancient coins. Often, the verdigris can be converted into a hard, crystalline mineral with a high Mohs index, as someone else pointed out in this thread. At that point, it should no longer be referred to as verdigris, it is not, it is technically mineral.

As far as verdigris forming a protective layer, it is true. Once an object is completely covered, the reactive copper sites become essentially inaccessible to fresh anion attack. However, the corrosion process is still active on a micro-scale as it is dynamic depending on many environmental factors (i.e. temperature, humidity, etc). Verdigris is quite complicated on a electrochemical scale! This is most evident with chloride ion where a somewhat self-perpetuating reaction occurs with the constant formation of fresh hydrochloric acid.

 

Reminds me somewhat of calcium carbonate which we now as crumbly chalk or as flaky limestone, but which is also marble.

 

If you think bronze disease is the same as other forms of copper corrosion, you have never seen bronze disease. Show an example of a coin cured by your product that actually had what you call self-perpetuating corrosion.

 

Whatever we want to call it, isn't it safe to say that if it's rock hard, you're good. If it comes off with a fingernail scrape...no good. So the stuff on the byzantine coin is sent off is ok, if you want to call it verdigris or a mineral.

this stuff, is not good whatever you want to call it (it's always BD in my mind). came off as a powdery residue with a fingernail scrape.



it appeared in months are was already eating into the surface of the coin (see the pitting where it was?). I did treat this with distilled water soaking, then baking followed by Verdi-care. for a year, its been like this (I got it out and checked it again right before this post..check your coins regularly!).

 

One would assume you are talking to @BadThad.

 

That makes me want to scratch!!! Myself that is...not the coin.

 

I would categorize BD as a malignant form of corrosion. Whilst verdigris is a former or chemical encrustation and change on a coins surface, as long as it does not continously or aggressively destroy a coin then that's good by me. Ultimately it boils down to eye appeal, condition and safety of the coin from a preservative perspective.