Cleaning a drachm of Menander I

[Frank M]

I posted something similar in the cleaning forum, but noticed some comments on there about how it had died off. Sorry, I apologize for the cross-post. It may be more appropriate to put this here.

I have worked on this coin a good deal. The encrustation on it is resistant to solvents, acids and bases that I normally use to clean coins. It is also resistant to electrolysis. The gunk feels like it is somewhere between thick creosote and soft lead.

I can get it to flake of and even come up in patches with a probe.

Here are photos close up on the an area where you can see a trench I've made in the gunk and a flake of it on the top of the coin. I have worked it off some of the inscription and there is a well-struck coin under this stuff.

Thoughts?

[Joe Sermarini]

It is horn silver. There is little benefit to removing it. It is made up of silver from the coin and is likely as attractive or more attractive than what would remain underneath.

[Frank M]

Thanks.

It did come off cleanly in some areas, show as nice strike underneath. You can see it most clearly if you look at the last Z in basileos and the first Z in soter. I am posting the original listing photo form Ebay where it is clearest.

Bummer

[djmacdo]

Common household ammonia will clean off horn silver, though it may well leave a corroded surface beneath.  If the process seems to stall completely, the horn silver is likely mixed with lime, which vinegar will remove.  Do not try the two solutions together--that would be disastrous.  After the vinegar, you could go back to ammonia.  But, again, you never know what sort of surface you might reveal underneath.  I have had some great results and some complete ruins.

[Frank M]

Common household ammonia will clean off horn silver, though it may well leave a corroded surface beneath.  If the process seems to stall completely, the horn silver is likely mixed with lime, which vinegar will remove.  Do not try the two solutions together--that would be disastrous.  After the vinegar, you could go back to ammonia.  But, again, you never know what sort of surface you might reveal underneath.  I have had some great results and some complete ruins.

Thanks! That's exactly the information I needed.

[Frank M]

I got it down to the metal and got all of the horn silver out through the use of an aluminum foil galvanization set-up and then white vinegar. I did the galvanization soak twice (with boiling water and baking soda)

I learned a lot!

This coin was never going to be perfect, and I know some people will disagree, but I like it brought down to the silver, if my other option is having nodules of horn silver on the coin.

[djmacdo]

I hate the foil technique.  Frequently it just turns the upper layer of the horn silver to silver and leaves the rest of it lumped up below and now makes it virtually impossible to clean by any other method. 

[Frank M]

I hate the foil technique.  Frequently it just turns the upper layer of the horn silver to silver and leaves the rest of it lumped up below and now makes it virtually impossible to clean by any other method. 

Thanks for the warning. I will keep and eye out for that when I have to clean horn silver in the future.

If I am understanding you correctly, I don't think I ran into this problem, but it is good to know about.

[Dino]

Nice job cleaning the coin.  I like to use CLR on silver coins.  Works well.  I have also used the foil method with some success as well. 

[Frank M]

Thanks! What is CLR?

[Dino]

Calcium Line and Rust remover.  Tip given to me by one of the large auction houses.  They use it on silver coins as well.  Don't use it on anything where you want to preserve a patina.  It will strip it right off.

[Frank M]

Calcium Line and Rust remover.  Tip given to me by one of the large auction houses.  They use it on silver coins as well.  Don't use it on anything where you want to preserve a patina.  It will strip it right off.

Better living through chemistry! Much appreciated

[djmacdo]

Around here we can find CLR in the grocery stores.  It is very strong--I generall prefer weaker solutions I can control better.  CLR will take things down to the bare metal.