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Definition Of "Patina"

 
 
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Valued Member
United States
206 Posts
 Posted 11/26/2007  9:52 pm Show Profile   Bookmark this topic Add Gold Certificates to your friends list Get a Link to this Message
I have seen this word Patina used a few times. Could you please explain the meaning of it, and why it is so valuable?

Also can you get Patina on gold? If so, how do you get it?

-Ben
Pillar of the Community
Australia
1252 Posts
 Posted 11/26/2007  10:13 pm  Show Profile   Bookmark this reply Add humpybong to your friends list Get a Link to this Reply

PATINA: natural colouring aquired by a coin, token or medal with the passing of time. It might also be the result of oxidation produced by certain soils, moisture or impurities in the atmosphere.
Valued Member
United States
206 Posts
 Posted 11/26/2007  10:19 pm  Show Profile   Bookmark this reply Add Gold Certificates to your friends list Get a Link to this Reply
"IMPURITIES in the atmosphere."

Is patina a bad thing?
Moderator
Learn More...
Australia
13138 Posts
 Posted 11/27/2007  02:02 am  Show Profile   Bookmark this reply Add Sap to your friends list Get a Link to this Reply
Being bright and shiny is not the natural state for most of the metals your coins are made up of. The formation of a patina is the natural consequence when a piece of refined metal (such as a coin) is kept in an oxygenated environment (like the open air) for a prolonged period.
quote:
Gold Certificates asked:
Is patina a bad thing?

That depends on what kind of coin we're talking about.

On modern proof and uncirculated coins, patina shouldn't have had time to form yet, especially if the coins have been stored properly. On such coins, "patina" would be regarded as a sign of poor storage, environmental damage (such as water or fire) or an attempt at creating artificial toning.

On older coins and coins from circulation, patina is considered normal and natural, and it's removal (by "cleaning") is generally frowned upon by coin collectors.

On ancient coins, patina is inevitable, and depending on the composition of the coin, the patina can be quite thick. All ancient coins need to be cleaned after they're dug out of the ground, but an ancient coin which has had it's patina completely stripped away to reveal the bare metal underneath is considered to have been overcleaned, and not as desirable as a coin with it's patina intact.
quote:
Gold Certificates also asked:
Also can you get Patina on gold? If so, how do you get it?

Gold is one of the few metals which is naturally resistant to oxidation at normal atmospheric temperature and pressure. Indeed, it is quite resistant to most kinds of chemical attack. As a result, pure gold doesn't form a patina. Slightly diluted gold, such as the .900 fine alloy used for American circulating gold coins, can discolour slightly because the copper in the alloy can form a patina. Gold so impure that a "real patina" readily forms has rarely been used as a coinage metal.

It probably is possible to create an "artificial patina" on a pure gold coin, but you'd need (a) some pretty noxious chemicals, (b) some high-tech gear, and/or (c) a lot of very expensive trial and error.
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
Bedrock of the Community
United States
18443 Posts
 Posted 11/27/2007  09:24 am  Show Profile   Bookmark this reply Add just carl to your friends list Get a Link to this Reply
It probably is possible to create an "artificial patina" on a pure gold coin, but you'd need (a) some pretty noxious chemicals, (b) some high-tech gear, and/or (c) a lot of very expensive trial and error.


Not completely true. Gold reacts with Sulfur fairly readily to form Ag2S and is usually noted as a Br/Bk discoloration on Gold. This is common in some areas of the country where high Sulfur Coal is burned such as the steel mills in Indiana. Mostly gone now. Other reactions that are normal are the formation of AuCl3 or AuCl4 where excessive Chlorine is present. And I thought everyone knew about Aqua-Regia and Gold to form 3HCl+1HNO3 or NOCl+Cl2+H OH pending temperatures, quantities and solution strength. And Gold can even be found in Organic Compounds such as [Au{CH2}2P{C6H5}2]2Cl2.
Patina is also very commonly mixed up with the word Verdigris found on Copper coinage. This is due to the common habit of picking up terminology loosely without investigation. In the case of Patina on Copper it is due to the normal Oxydation process forming Cu2O. However, this is the brownish tone to Copper first observed. Then further reactions with moisture and Carbon Dioxide form Copper Carbonate [CuCO3-Cu(OH}21] and that is the so called Greenish Patina on copper coins.
just carl
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