How to remove EXTREME encrustations?

Starting conservatively is excellent advice but after a very, very, very long soak, the coin may be ready to actually start removing something.

 

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So far I've tried the following with a couple of trashier coins to test.

1. Electrolysis. This did almost nothing, except remove patina from the high points and reveal shiny copper.

2. Lemon juice. Even leaving coins in the juice for about 6 hours did dislodge some green gunk, there was still little to no use. All it did was remove even more patina.

3. Apple cider vinegar. 6 hours later, absolutely no change.

Conclusion: none of the above methods have any impact on literal rock.

So, what dissolves granite and not metal?

 

I do not think it is granite or quartzsite and almost any strong chemical would attack the weakest chemical part ( metal coin) first. If you can physically chip off the material to satisfy you that is probably the only one. If the contaminant found a way in cracks or flakes on the coin, it has probably formed similar matrix inside.Archeologists also sometimes resorts to rotary dental burrs to remove matrix around fossils. One thing I find hard but necessary, is to give up on curiosity when it costs more time and money than it is worth. Good luck, Jim

 

I agree. There is a point that I move on, and use my time for other interests.

Personally, I just have no patience to clean coins. I never purchase uncleaned lots, and have only one coin that was cleaned. And that was cleaned by a friend wanting to prove his formula. For me, it is not a mystery, rather a frustration, so I just “pass” on buying uncleaned coins.

I do enjoy giving out coins. I had a bag of LRB folles that I have given out to my Grandkids, friends, etc. (would that be a redundancy using bag and folles in one sentence?)

 

I'm not married to the coins, and they cost only $0.81 each so it's not the end of the world.

What I'm really torn up about is the first coin in the initial post. it's large 28mm, and the underlying coin has SHARP detail.

With no other quick option (don't feel like soaking in olive oil for half a year), I'll sacrifice this one to the Lye Gods... I'm just WAY too curious to see what's underneath.

 

I have quite a few coins like this and ended up just leaving them be but will probably take another crack at them sometime. I imagine using a metal dental pick would just make things worse? If you're willing to play the slow game, leaving them to soak in distilled water and taking them out once a week or so to agitate the encrusted areas with a wooden toothpick and toothbrush may eventually produce results, although this could take up to several years. At that point, it obviously isn't worth it from a monetary view, but most of us that enjoy the cleaning and identification process are doing it because we love it.