How to remove 'encrustation' from R.R. coin??

I inserted few pictures to have your opinion

thanks in advance

 

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that's a weird coin. Something looks off, I wonder if it's authentic.

If it is real, I don't know what really could be done. The globular encrustations appaer to be the same color, which often means that removal of them will absolutely destroy the patina and leave it pitted. Will stay tuned for other remarks

 

For me it was one of the characteristics of silver bromide those bubbles and I am not sure it is patina more a layer of Bromide. I am quite sure of authenticity though

let s see what the others will say thanks for your comment

 

Is the coin silver? If so, then the method that @Topcat7 described, using sodium thiosulfate, at the top of this thread might be worth a try. I would be very interested in hearing what you decide to do and what your results are.

 

Yes silver

 

Well, sodium thiosulfate certainly won’t HURT anything. You usually can’t fall foul of thiosulfate.

 

It's good this thread was revived as I saw the term "horn silver" but never understood exactly what does it mean and how to get read of it.
Would you say these 2 coins have horn silver too?

 

yes, certainly looks like it.

 

If genuine, a denarius of Claudius is a rather rare coin. If you need to ask for advice, you probably shouldn't attempt to clean it yourself.

 

I might give it a try with the thiosulfate, however I have no idea where to get this from.

Is this destructive for the coin (on a long term basis) or just aesthetically unpleasant?

 

do you know any specialist able to do it ?

 

you can get it on internet it is quite cheap

 

On holidays, so brief reply. Silver chlorides can be found in this granular form. In fact, I encounter them usually on coins of high silver content.

You can indeed immerse the coin in sodium thiosulphate, following the instructions outlined above in one of my earlier posts. Sodium thiosulphate will not harm silver in any way; there is however a risk of pitted surfaces below the deposits. In my experience though, this type of deposits clean up quite nicely.

 

Not sure if you mean my guide (since I mentioned creating a guide on horn silver removal)? It’s sort of finished, and it is available upon request per pm.

In the past two years since this thread I’ve mainly cleaned high-end coins, both of my own collection as well for clients. I’ve posted a few threads on chemical conservation of coins - see my post history.

 

I've just PM'ed you. I was curious about the Sasanian drachm that you said you were going to clean next. How did that turn out?

 

There appears to be some confusion. Topcat asked for help on his coins, and I provided the information. I did not clean his coins (at least, I don’t remember)

 

Oops. You're right. My mistake.

 

what is this sodium thiosulphate? I’m gamiliar now with purchasing sodium sesquicarbonate and using it as a 5% solution, but I know nothing about the chemical you cite. Could you elaborate on it’s safety profile, forms, where it can be bought, how expensive, etc? I’d appreciate it. And also, please let me know if you create a guide, and how to obtain it. Thanks, Joe

 

no downside here compared to the horror before. Very nice job!

 

Here's the one I got:
https://www.ebay.com/itm/391427730454?hash=item5b22e92c16:g:lOQAAOSwjdFei9~W

$7 a small jar.

Na2S3O4 x 5H2O

Whatever that means.