CLEANING COINS! PLEASE HELP!

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How old was the roof you restored?

I can't really justify continuing a discussion where one may see a patina and another just corrosion (the "another" being wrong in my opinion). Meanwhile the corrosion rate can be less than 0.4 mm in 200 years (in some climates, fully exposed to the elements). That's 3 to 4 generations that have the opportunity to keep a green smooth patina on an old copper in an air tight and a plastic bag, preserving it's unpitted, uncorroded and undamaged appearance for possibly another 400+ years. By that time, green patina will be accepted worldwide as a patina.

Cheers, on a friendly note.

 

Yes, you can help yourself. Such postings are not acceptable. You imply you have higher ethical standards in previous postings in this thread, and then this post ( removed)!

 

I hope I didn't come across as high and mighty, that wasn't the intention. As for the deleted post and reprimand, my thoughts and arguments regarding the deleted example, remain valid, truthful and most importantly, correct.

Yes there is right and wrong in that. We'll just have to agree to disagree. Your fellow staffers have your back and most of my arguments will be deleted. This round goes to you and the bodyguards. Cheers!

 

No, no, no. I am calling BS on this Doug. A green patina has NOTHING AT ALL to do with verdigris or bronze disease. They are chemical completely different, and to infer they have ANYTHING in common is to confuse and mislead anyone reading.

A hard green patina on a coin is a very stable, (and in ancients very desirable and expensive), patina formed on copper coins. Verdigris is a chemical disease which will rot metal if left unattended. Yes, verdigris is corrosion, but a hard green patina, (which I have personally seen on US coins as little as 80 years old), is not.

Those are the facts, Doug.

 

NO, NO, NO, it's strawberry and vanilla. Kidding, enough said. Is there any way I can get the "Ignore" option for Staff Members added to my profile. It might make it easier to get away with writing "stuff". Take care, I'm moving on...

 

Oh darn!

Well, since I'm being watched anyway, are you aware of what this paragraph reads and sounds like? It's one step away from being an ad for that modern day little blue pill...

 

I have never heard this postulated by anyone. Verdigris, a powdery light green powder magically transforms into a blue, darkgreen, or black, (since all three of these colors are seen interchangably on coins by the same chemical reaction). I simply have nothing to say if this is your hypothesis. I simply hope someone like Doug Smith or Badthad, who would be in a better position to chemically refute this, reads this thread.

 

I always liked a brillo pad the harder the better , or a rock tumbler . But throw away the rounded rocks and use carbide cutters that have been whacked with a hammer . Oh I forgot hitting it with a hammer really loosens up any of that pesty dirt .

 

Nobodys' as old as Green , he was with Noah on the Ark . Sorry Ken , just telling the truth .

 

Perhaps the terminology ~ verdigris, bronze disease, patina, corrosion , adds to the confusion. Assuming we are speaking of copper alloy coins and not silver, they can all apply, and relate to the formation of a chemical compound of the copper and an anion that can vary from sulfide, carbonate, oxide, etc. Many of these compounds can be a different color if hydrated (water added), For example copper(II) sulfate is slight greenish white, but when each molecule is hydrated with 5 water molecules ( copper(II) sulfate penthydrate ) it is a deep blue which we recognize 'colloquially ' as Copper Sulfate. So you can have many color, many physical structures ( crystals) , many different reactions on these coins ( even the same coins) . For instant, Copper Carbonate is more green, copper sulfate more blue, copper oxide reddish, copper sulfide blackish.

But ( sorry Chris) they all involve the reaction with the copper of the coin, so is a % of corrosive action on the metal. Microscopic layers will be invisible, but the more the _______________( add any of the terms, in first line), the more damage to the coin.

Jim

 

I guess tarnish on silver is also a corrosive reaction. Now the whole discussion seems rather pointless. The only question that remains is, "Can you accept green in your collection?".

"Tarnish can be removed by using steel wool, sandpaper, emery paper, baking soda or a file to rub or polish the metal's dull surface"

They forgot to mention ash from a fire place, my personal favourite.

 

Don't be sorry Jim. My only question would be is the same chemical bonding that occurs during verdigris then same chemical bonds of hard green patina? I always thought verdigris was a chloride, but badthad knows this chemistry better than I. If its the same chemistry, how can badthad's verdicare remove verdigris and not touch in any way green toning?

 

Thanks all.

I have to go now.

I need to go buy some Brillo pads!

 

http://www.crescentcitycoinclub.org/seminars_and_programs/Bronze Disease.pdf

Here is a presentation by a chemist on bronze disease versus patina. A patina is a stable oxide, and bronze disease is a self perpetuating acidic reaction. This reaction will continue until the coin is consumed or the acid neutralized.

Another point I would make is Verdicare from Badthad I have had remove bronze disease on green, black, red, and brown patina coins. On not one of the coins did the verdicare affect the patina, even after soaks of over 2 days. However, the bronze disease was removed. So, are you trying to say a coin gets bronze disease over and over, and these layers of bronze disease somehow magically transform into layers of stable oxides instead of damaging acids?

Sorry, still not buying it unless someone shows me the chemistry. This subject has been discussed ad nauseum on ancient coin boards, and not once have I ever heard someone suggest bronze disease "builds up" stable patinas.

 

Asked to voice my opinion here....

No matter the name, verdigris, bronze disease, etc., it's all the essentially the same thing. Verdigris is corrosion that forms from the reaction of copper with an anion. The composition can vary widely and be VERY complicated. Nonetheless, the basics of initial formation is identical - water and air (feed materials) start the reaction. Ancient coins can be extremely complicated because you can form copper-based minerals - which are very, very hard. Again, it's a simple evolution of verdigris - it changes based on the feed materials, time, temperature and pressure.

As for a "protective patina", that is basically correct in that all of the copper surface becomes reacted leaving little room for new reactions to occur (the statue of Liberty is a good example). Nonetheless, the corrosive reaction will still continue on a slower scale. Unless all feed materials are removed from the equation you cannot completely stop the process unless you store your copper in a perfect vacuum.