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Nero denarius - horn silver?


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Hello all. I recently purchased a Nero denarius that to me looked partially uncleaned, thinking the dark areas were hardened junk I could remove. Well, after a few soaks in ammonia+water, as well as some soaks in lime juice, I've made little to no improvement on the coin. I looked at it a little closer and the bluish-dark grey areas I was trying to remove have some somewhat rough areas to it, and seems to be a layer on top of the original surface, as evidenced by the edges where it there is a clear line of where it ends and it looks "taller" than the normal grey silver surface on the edge. My guess now is that it is some form of horn silver. What do you think? Any recommendations to cleaning it or at least making the darker patches lighter? If I remember correctly, at least a couple of members here have had success in removing horn silver ( @Roerbakmix?)


Edited by ValiantKnight
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Thiosulphate did the trick for horn silver but I've had a few issues sometimes, even when I was successful: 1. the coin changed the color to dull gray and I was not able to clean it completely 2. (this shouldn't be your case) - the horn silver layer masked some pretty advanced corrosion. 

Before and after 






Especially on the  2nd coin, I think cleaning it was not a correct decision. 


Yours should not show pitting underneath, but just telling for future references. 

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Yeah that looks like horn silver, maybe treat it with sodium thiosulfate, you might lose significant portion of the weight but the details could pop up nicely, below coin was probably cleaned a similar way before i even bought it.


Edited by JayAg47
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Thanks for all the helpful posts, really appreciate it and glad to have confirmation on what it is (well, glad in knowing what it is, not that its horn silver lol). 

16 hours ago, Roerbakmix said:

Anhydrous sodium thiosulphate will do the trick. I suspect this coin will not improve though; this type of horn silver (thin layer, no clear demarcation) usually covers a putter surface.

I may decide to leave it for now, at least until I get an upgrade. I know next to nothing about sodium thiosulphate (I do know though that it comes in crystalline form), so are there any safety precautions I should take (apart from the obvious like not ingesting, not getting it in the eyes, etc.)? 

The normal gray silver/non-horn silver areas don’t have any major pitting, so could this be a positive sign that the surface under the horn silver also lacks pitting?

Also, by any chance might you have some before and after photos of similar coins to mine that you have treated? So I can get a further idea of how it could come out? 

Thanks for your help!

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Ok so I’ll admit curiosity got the better of me and I ended up buying sodium thiosulphate and gave the coin a very hot bath of it. Left it in for some time, took it out, picked at it, and it seems promising. A few small areas of the horn silver on the obverse (neck area), not much, I was able to remove, and the silver surface that was uncovered looks good, no signs of pitting. Negligible progress on the reverse, but I chalk that up due to the coin being obverse side up (the side I’m most interested in). Since it’s an extensive case of horn silver I’m going to continue giving it the baths, and I’ll post the denarius once I feel that I’m done and I’m satisfied with the results.

Edited by ValiantKnight
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