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FORVM`s Classical Numismatics Discussion Board  |  Numismatic and History Discussions  |  Coin Photography, Conservation and Storage (Moderator: bruce61813)  |  Topic: What does this J Caesar denarius suffer from? 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: What does this J Caesar denarius suffer from?  (Read 2401 times)
Anders
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« on: July 13, 2006, 06:08:06 am »

Hi!

Maybe someone at this forum can tell me little about "the surface disease" this J Caesar denarius suffers from?
The pictures are caught through Google from heritageauctions.com at their auction 410, lot 12088

/  Anders
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bruce61813
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« Reply #1 on: July 14, 2006, 11:41:12 am »

Since this is silver, one of the possibilities is "horn silver" , that is a chloride attack on the silver alloy, similar to bronze disease. One of the possible treatments is using  photograhic fixer -
the thiosulfate, it will break down the sliver chloride, but there is a caution, it will dislove elemental silver, so the recommended proceedure is to work with it diluted as recommended for photography. It won't hurt the solid silver, but the chloride for will be dissolved.

Bruce
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peterpil19
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« Reply #2 on: July 14, 2006, 09:48:22 pm »

Since this is silver, one of the possibilities is "horn silver" , that is a chloride attack on the silver alloy, similar to bronze disease. One of the possible treatments is using photograhic fixer -
the thiosulfate, it will break down the sliver chloride, but there is a caution, it will dislove elemental silver, so the recommended proceedure is to work with it diluted as recommended for photography. It won't hurt the solid silver, but the chloride for will be dissolved.

Bruce

Hi Bruce,

One thing I've been curious about horn silver: what is the rate of reaction compared to bronze disease (under same conditions)? I assume it would be much slower, but is it slow enough to warrant leaving the coin be? Or is treatment essential?

--Peter
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bruce61813
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« Reply #3 on: July 18, 2006, 07:24:50 pm »

I really don't know. there has not been anything really written about it. People talk about it on occasion, but nothing seems to be really put forward. I think it is is slower, but just as damaging. the use of hypo would not further damage the coin, it would remove the AgCl and pobably allow for the coin to be soaked in distilled/demineralized water to remove the rest of the salts.

Bruce
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Aamil Q
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« Reply #4 on: November 06, 2006, 09:28:15 pm »

Would a lemon juice soak work?
Aamil.
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bruce61813
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« Reply #5 on: November 15, 2006, 09:18:42 am »

Would a lemon juice soak work?
Aamil.
Lemon juice would not work if it is horn silver, the lemon juice is generally good only for normal oxidation.

bruce
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curtislclay
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« Reply #6 on: November 15, 2006, 09:37:20 am »

Your denarius looks lightly corroded and cleaned.  It looks stable to me, rather than actively deteriorating.
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Curtis Clay
Aamil Q
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« Reply #7 on: December 18, 2006, 12:25:32 pm »

Does anyone know where I can find some of this hypo stuff Bruce mentioned? Can I order it online, and is it cheap or expensive?
Aamil.
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bruce61813
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« Reply #8 on: December 18, 2006, 12:53:42 pm »

Does anyone know where I can find some of this hypo stuff Bruce mentioned? Can I order it online, and is it cheap or expensive?
Aamil.
You can buy it on line, if you are in europe, check any photograhic chemical supplier, but here is one source of many http://www.photoformulary.com/DesktopModules/StoreProductDetails.aspx?productID=141&tabid=9&tabindex=2&categoryid=3&selection=0&langId=0
 or the tiny url http://tinyurl.com/y5pv7v. this makes a liter, whickh will last a very long time as it doesn't spoil. I would soak the coin for 5 minutes, then lightly scrub it, ad try another 5 minutes. This solution will not harm pure metalic silver, but will disolve silver chloride.



bruce
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Carolus Magnus
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« Reply #9 on: December 18, 2006, 07:19:22 pm »

Could this be a case of porosity?(sic) I would think the weight of the coin would be helpfull. If this is true, I doubt that any chemical bath would help, and may actually damage the coin further. Just a thought, I must defer to the experts on this idea....................CT
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bruce61813
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« Reply #10 on: December 19, 2006, 01:07:15 pm »

Quote from: Carolus Magnus on December 18, 2006, 07:19:22 pm
Could this be a case of porosity?(sic) I would think the weight of the coin would be helpfull. If this is true, I doubt that any chemical bath would help, and may actually damage the coin further. Just a thought, I must defer to the experts on this idea....................CT
I don't think porosity applies in this case. It generally applies to bronze coins that have been almost totally eaten by BD, the tin is removed from the bronzr matris and repaced by something else, hence the porosity. These silver coins are generally attacked onthe surface, and are etched, so the treatment would stop the surface damage, nothing will replace the damage, but if it isn't stopped, the damage continues.

Bruce
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Carolus Magnus
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« Reply #11 on: December 19, 2006, 03:01:09 pm »

But what of the silver coins that are underweight? I always assumed porosity. maybe crystalization? I guess I am trying to understand what causes a silver coin to weigh less than it should. Assuming it is silver, and of an average flan size.
                                                                          Chuck T
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Howard Cole
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« Reply #12 on: December 19, 2006, 03:19:51 pm »

Porosity does happen to silver coins because they are not pure silver.  The copper or other alloying material is slowly dissolved out.  It is very common in sea salvaged coins.

There are also other reasons for a coin to be underweight.  So of these are clipping (removing some of the silver from the edge of the coin using clipper or shears), filing (filing off some of the silver from the edge of the coin), and sweating (putting a bunch of silver coins in a box or leather bag and agitating them until a little silver is scraped off of each coin).  Also the coin may have come from the mint slightly underweight. 

Not every coin was weighed to make sure they were at the correct weight.  Usually a small sample from a batch was weighed.  If their weight was good, the whole batch was released from the mint.  The mint was given a certain amount of metal and they had to make a certain number of coins from the given amount.  So if a few coins were overweight, some would also have to be underweight to make the specified number of coins.
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FORVM`s Classical Numismatics Discussion Board  |  Numismatic and History Discussions  |  Coin Photography, Conservation and Storage (Moderator: bruce61813)  |  Topic: What does this J Caesar denarius suffer from? « previous next »
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