Remove Lava From Coin?

I have soaked these for months, even years. I have several that are in olive oil I acquired nearly 3 years ago. I change the oil about every 4 or 5 months and they are starting to look fairly good. I don't have a tumbler and I would be scared t use a glass bead peening method. Good luck with those.

IMO olive oil is the best method, followed by distilled water. The object is to remove the caked on dirt but not hurt the coin or remove the patina. It's not as simple as it sounds, every coin is different depending on what type of soil it was burried in and it's exposure to the minerals in that soil. A long soaking in olive oil softens the dirt and allows it to be picked off without removing the patina. It takes practice and you will probably overclean some coins before you get the hang of it.

Thank you, Bensgemz. I know zip about ancient coins, but I did find that (almost) same image in Google Images, and I think you nailed it exactly.
I just bought ten more of these. There are times when olive oil and acetone just won't hack it. Some coins are so covered with ages of crud the details are obscured until they are "restored". I have an 1823 large cent that I got for a dollar at a flea market many years ago. It languished in a box of "unknowns", until I retired. A coating of hard tar-like, but insoluable, substance hid nearly all detail until I cleaned it last month. It came out with a readable date, and almost all lettering visible on the reverse.
However, before I get flamed, let me be clear that I'm not advocating EVER using a sand blaster on ANY coin. What I am doing here is just a personal experiment on coins so badly damaged as to have only their intristic metal value. I poke around with a metal detector, mostly for the exercise value, and most of the clad coins I find can not even be spent; they look that bad. After one or two sessions in the tumbler, even IHOP will take them. Thus, I get a "free" breakfast a couple times a year.

There is one key diference between a modern detector find and an ancient uncleaned coin: the nature of the surrounding "dirt", because not all of it's really "dirt".

The problem with using any harsh-but-quick cleaning method on an uncleaned ancient coin - be it acids, electrolysis, a rock polisher or a sandblaster - is stripping away too much patina, because on many surviving bronze coins it's in the patina rather than the metal itself that has most of the fine detail preserved.

A bronze coin that's been in the ground for 2000 years has begun to fossilize, with the copper slowly trying to turn back into the copper ore from which it was made. So the cross-section of an uncleaned bronze coin typically has three layers:



The goal with cleaning ancient bronzes is to remove the brown "dirt" layer while disturbing the green "patina" later as little as possible, because it's the outermost surface of this green layer that marks the original surface of the coin, and that's where the fine details are going to be preserved. Stripping both the brown and green layers away leaving just the orange metal core will result in a coin that's been "overcleaned", and typically looks pitted and fuzzy. Judging from the colour and appearance of the coin in your pic, I suspect that's what's happened to your coin.

Unfortunately, not all uncleaneds have a nice, sharp boundary between the "brown" and "green" layers. The "brown" layer can look quite greenish as copper leaches out into the surrounding soil, and minerals leach into the patina layer to replace it.

Thanks to all of you for all the information, and excellent tips and advice.
At my somewhat advanced age(In my youth, I could still find the occasional Indian Head cent in circulation, all the hint yer gonna get), I have neither time, nor patience to let the olive oil and DW to work their magic. I'm a retired tool & die maker. I worked nearly forty years for an excellent computer company before retiring over 13 years ago. I still dabble in the black arts, alchemy, trying to make gold from lead(Just kidding. Never take me too seriously). I do have a semi well equipted shop in the garage.
My current brain storm is to redesign my sand blaster into something more useful for cleaning coins; something more like the cosmetic surgeons use for dermabrasion, but without the $10K price tag. A small, ceramic nozzle, very fine grit(baking soda?), lower air pressure, and an adjustable grit feeding system. One of my friends used to cut heart stents for a living, using a laser, so there may be some merit to using that method as well.
Like Benzgemz, I use a stereo microscope to pick away at the coatings with a dental pick. It is a technique which now seems primative, tedious, and nearly fruitless, given the techno world I (we) now live in.
I 'spect I rambled on way too long for this thread to be relavent, but I would love to know what you think about the ideas.