Share my fun: describing and cleaning a small roman hoard

Found some time to clean another two, nrs 11 and 12:
Nr 11:

Unfortunately, the coin showed some roughness. Still, in hand, it's a nice coin. The copper deposit on the radiate crown took some time.

Nr 12:

This was really fun to clean. It took about 45 minutes.

 

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This is the best reason for cleaning uncleaned coins. If you enjoy the process ten times as much as the coin is worth, you are are real winner. If you are prone to stress and prefer to buy types of your choosing, you will be better off buying professionally cleaned coins or even castoffs from people who cleaned 1000 coins and have 100 each of several types. That is what makes the hobby fun - you can have it your way.

 

@dougsmit I agree. This small hoard of 15 coins gives me the opportunity to try out different cleaning techniques on heavily encrusted coins of roughly the same composition.

The remaining three coins will be posted later.

 

Great cleaning results!

Any updates on this group?

What happened to them after being returned to the owner?

John

 

The coins were returned to the owner. He found the coins a few months before this restoration project. Overall, I was not super happy with how it turned out, but he was very exited.

 

This is a very interesting thread. This is the first time I've heard of using oxalic acid or sodium thiosulfate (Wikipedia describes it as more of a medical product). I think your results are very creditable. Can you give us any tips about which product to use when? You seem to use oxalic acid first and then sodium thiosulfate. I imagine any kind of acid helps dissolve incrustations, though it should obviously be used sparingly, but what does sodium thiosulfate do? This was very informative. Most online advice is just "don't clean coins", but that's no help if you can't even make out what they are.

 

Hi, thanks. I've posted many guides on the restoration of silver ancient coins (which I regularly do). If you search my posting history, you'll find some examples, usually with an explanation of the procedure.

In short, you'll have to know what encrustations can be present on a coin, and then find a chemical that dissolves only those encrustations without harming the coin, or harming the patina. Coins of lower purity are difficult to clean for obvious reasons, and this little hoard was of low silver purity. I'm not a particular fan of oxalic acid, though it might have its merits on ferrous oxides (the brown deposits), which are terribly difficult to remove without harming the silver.

I just really love cleaning coins with horn silver. It's usually super easy and fun, provided you recognize those that benefit from cleaning beforehand (which requires experience).

 

Hi @Roerbakmix , really a great job! Can I ask you which percentage of sodium tiosulphate do you put in the solution for cleaning the horn silver? And how hot it should be?

 

Thanks! There is no 'one size fits all' answer. It depends on the deposits and the coin. Regarding the concentration: some thick deposits require higher concentrations (e.g. 5g / 30ml purified water) whereas others require more diluted concentrations (e.g. 1g / 30 ml purified water). Regarding the temperature: care should be taken to gradually increase the temperature. I usually heat the solution to c. 60 C and gently drop the coin, then after a minute or so, I create a new solution at c. 100 C.

Also, note that sodium thiosulphate is rather instable and will degrade in sulphur, amongst other. This may cause a thin yellow deposit on your coin, which you want to avoid. Hence, I don't use my solution for longer than 1-2 minutes.

 

Thank you very much! I have used sodium tiosulphate for removing horn silver with mixed results, sometimes it was immediately effective sometimes less. But I used so far a very lower concentration compared to yours and never hot water.

 

About the yellowish colour resulting after soaking the coin in s.t., I experienced that it can be easily removed wrapping the coin in a tinfoil (shiny side in) and soaking for a few minutes in simple boiling hot water.

 

I personally never use this method, as it will also remove the silver sulphate from the silver coin, thus resulting in a shiny silver coin.

 

I refer to cases like this, where you can hardly find a nice patina under the thick encrustation

 

This is exactly what I meant: you'll end up with a shiny coin.

You may actually find a nice silver sulphate patina beneath the horn silver depositions:



This coin was cleaned using sodium thiosulphate only for about 10 minutes, using (if I remember correctly) three to four new solutions at different concentration.

 

@Roerbakmix wonderful results! The next time I’ll use your method, preparing the different solution in advance (and hoping not mess it)