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Author Topic: Sad experience  (Read 1742 times)

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Offline Numerianus

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Sad experience
« on: April 16, 2006, 04:08:30 pm »
Taking into account that the hole annihilates the value of this Elagabal denarius, I made an attempt to clean
it using ammoniac. The result is negative. The chemical  processes transformed silver into some black stuff which
was dissolved by ammoniac revealing rather irregular surface. Moreover, some parts of  remains black because ammoniac
did not react properly  everywhere...

Offline Jochen

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Re: Sad experience
« Reply #1 on: April 16, 2006, 04:26:50 pm »
It was a nice coin before!

Offline Robert_Brenchley

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Re: Sad experience
« Reply #2 on: April 16, 2006, 07:03:29 pm »
What's the precise substance you used? The term 'ammoniac' isn't current on this side of the Atlantic; the nearest I can get is sal ammoniac, which is ammonium chloride.
Robert Brenchley

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Offline Numerianus

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Re: Sad experience
« Reply #3 on: April 17, 2006, 04:28:46 pm »
French stuff: 20.5% ammonia.
 
After this experiment  I arrived to a conclusion that miserable silver coins,
apparently, suffered from a harsh cleaning, which are  sold in mass by Bulgarian dealers, also
were nice before...

Offline Robert_Brenchley

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Re: Sad experience
« Reply #4 on: April 17, 2006, 06:45:48 pm »
A great many silver coins have been harshly cleaned, but don't despair of them. As long as there's no mechanical damage, they will tone in time. I have a Severus Alexander den which I harshly cleaned myself three years ago this month, to get rid of some irritating greenies. It's now developing the beginnings of cabinet toning, just from sitting in it's flip. Other coins may take a lot longer, but they will get there in the end.
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Offline Numerianus

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Re: Sad experience
« Reply #5 on: April 18, 2006, 02:41:48 am »
The problem is not with the toning (tarniching). The substance removed covered the surface regularly and  id of the shape
of the coin at the moment  when it stop circulation. The remaining
metal has ugly pitting and iregularities.  I had another negative experience just by frotting a nice silvered follis.
The silvering  was transformed by the temp in a black substance which was like a thin powder. After removing it the coin
becamme much flatter  and lost its charm.

Offline Robert_Brenchley

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Re: Sad experience
« Reply #6 on: April 18, 2006, 06:06:18 pm »
I can see it's corroded, but that was probably there in the first place. I think I might have left it as it was, but I didn't have it in hand, so it's hard to judge.
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bruce61813

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Re: Sad experience
« Reply #7 on: April 21, 2006, 06:03:39 pm »
  I believe Robert has it correct. The rough surface ansd the pitting were there, just filled in with the dirt and copper oxide. A true silver coin vs a slivered broze coin are two different things. A true silver coin is rarely bothered by acids or ammonia. But a silvered broncze coin is very different. There is offten a corrosion layer, oxidized copper, thet runs under the silver, and when the coin is cleaned, that layer is disloved, there is then nothing to bond the silver to the bronze or copper base, so it flakes away. There may be other reations also, so you must take into account the possible metal vs cleaner reactions. That is one reason for not using most acids on bronze, but you can use the same acid on silver.

Bruce

 

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