FORVM`s Classical Numismatics Discussion Board
Numismatic and History Discussion Forums => Uncleaned Ancient Coin Discussion Forum => Topic started by: Numerianus 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...
-
It was a nice coin before!
-
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.
-
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...
-
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.
-
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.
-
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.
-
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