I know that it's a resounding NO on moderns, but what about ancients? As I look through ancient coin websites, it appears that lots of cleaning is goin' on. If it's acceptable, what's the best method?
I don't collect or remotely know anything about ancient coin collecting, but I think what your referring to is "dipping", which is market acceptable.
It depends largely on what it is that you're cleaning. Every ancient coin needs some level of cleaning at some point, as they are pulling form the ground covered in dirt, but there's definitely a point of overcleaning, where you remove the patina and leave something shiny. You don't want to go that far. Anyway, if you're buying coins listed as "uncleaned", then you almost always want to clean then (I've managed to get a couple that had rather nice desert patinas that I didn't want to touch), but you usually don't want to clean coins not listed as that unless you know what you're doing, since they're usually already cleaned to a decent level. If you have some coins that you're curious about, post some pictures, and we can tell you whether it would make sense to try to clean them.
There are known and acceptable methods for cleaning ancients. In order to know what to recommend, we have to see the coins now. Generally, you want to do as little as necessary to the coin. If it has dirt soil earth ground in it, then dish soap and warm water are fine to remove that. NEVER EVER scrub a coin. (See exceptions below.) Abrasion removes the surface and the surface cannot be put back. Pat it dry, do not rub it dry. Stealer is wrong: do not "dip" an ancient coin. Jeweler's dip is an acid. Americans use it to remove sulphur toning from their Mint State coins. It is not appropriate for ancients. First of all, the metals, while nominally "silver" are different. Ancient silver crystalizes. Ancient silver was struck hot, not cold like modern silver. With ancients, especially those recovered directly from the ground, you get "hornblend" and other silver compounds that are not easily washed away with an acid rinse. With ancient copper coins, there are people who use BRASS brushes on the theory that brass is softer than bronze and copper. Myself, I have never done that. Also with copper, some people prefer to soak the coin in olive oil for 30 days. (You waited 2000 years: what's another month?) Then wash the coin in mild soap and water. More could be said, but we would need to know more about your coin(s).
Thanks for the info mmarotta. What kind of "cleaning" is market acceptable in ancient coins? I know dipping is market acceptable for moderns (Morgans, Seated coins etc) :too-funny: Personally I don't like dipped coins.
Ground rule #1: ALL ancient coins have been cleaned. Uncleaned coins with an inch of dirt on them used to have two inches of dirt. Ground rule #2: If you can look at the coin and tell what was done to clean it, the cleaning could have been done better and could detract from market value. If the coin looks natural, it will be OK in the market. Ground rule #3: Many ancients are scarce enough that there are not enough pristine, natural looking examples to meet demand. These have market acceptance in well scrubbed condition. Other coins exist in such numbers that collectors turn their nose up at any imperfection including less than professional cleaning. Ground rule #4: Cleaning ancients is an art some of us never master. If you only ruin half of the coins you touch, you are at least average if not better.
A good start is soaking them for several months in distilled water (not tap water, not mineral water). Change the water a few times along the way to freshen it up and get rid of the dirt that's coming off easily. Given enough time, a lot of the muck should loosen up. It won't be enough for most of the coins, but you'll be able to better tell if you're dealing with unidentifiable slugs or something with potential. Try gently brushing with an old toothbrush to see what crud will flake off without much help. An olive oil soak for a similar amount of time should be the next (messier) step. Only after exhausting these gentlest of techniques would I up the stakes for more stubborn coins, with electrolysis being the last resort for some ancient coin cleaners. There are dozens of ways to torture the dirt off of ancient coins, and plenty of articles on the subject that can be quickly goggled. Read up on it before you do damage to an encrusted coin that might have otherwise turned out to be an interesting collectible.
Lots of websites to help, and most of the good advice has already been given here. Slow and gentle is best, you may get some good coins. You will get a lot of slugs regardless of how you go and coins you buy though. Its ok for a hobby if you enjoy the effort, if you enjoy coins I would say you are better off buying cleaned ones. Easier and usually cheaper overall.
This weekend I went to a show and bought 20 cleaned and common late Romans from two different dealers for prices ranging from $5 to $7 per coin. One would grade EF but most were F-VF and had legible mintmarks allowing full ID. The question here is whether your thrill of the hunt is satisfied by the search for coins like I bought or whether you have to remove the dirt and be the first person to see the coin. Certainly uncleaned coins offer a one in a million chance of getting a really rare coin and the chance of my getting one is considerably less. Obviously what I bought were not rarities. How many slugs you tolerate for that additional hope of a special coin is a matter for us each to decide. I prefer coins cleaned before I get them. You may have a different hobby. I might add that the difference between the $5 and the $7 coins was the dealer more than the coins. There were other dealers there with similar coins for $20 but I did not buy them. At some point you will probably have enough of the common types that you stop buying $7 cleaned or $2 uncleaned coins and have to raise your price point to get different things. As it was, I accidentally bought a couple duplicates. Out of a hundred uncleaned coins, how many are duplicates?
Another point to consider with uncleaned coins is that by and large they have been checked. Trust me, the diggers and subsequent wholesale buyer are much more adept than we are at spotting rarities, even under the dirt. This is their living that they do everyday. I have met one person who buys from the field in Eastern Europe and he can tell you almost every coin type even covered with dirt. Basically, you cannot buy unsearched uncleaned coin, the best you can hope for is horribly covered mess might have something good underneath, but in my experience you will get a very high cull rate, lots of common, low grade coins, and a chance at something better. Effectively most uncleaned coins are culls not worth cleaning, but for some reason Americans love buying them. If the OP still wants to buy them, PM me and I will give you a couple of good pointers that will up your success rate, as I know I am talking bad about them here, but I have made some money buying certain types.
With regard to advise to let experts do the cleaning of Ancient coins, I don't know about that I was reading an article about a year ago where at an archeological site they had found a bunch of coins and the Graduate Student in charge of cleaning them lest them in a solution accidentally overnight just to come back and find that all the coins had dissolved into a lovely blue solution I'll see if I can find that article or blog. Ruben
Archeologists are horrible coin collectors and cleaners for the most part. Archeologists stand on the backs of coin collectors who have dated the material they use to date their finds. This is why it is so frustrating the current anomosity between the two groups.
That doesn't surprise me, but a professionalization of Numismatics, which is not necessarily the same as coin collecting, with University Programs as a subsection of archeology might go a long way to smoothing over this problem. I don't know how feasible that is, but it is the path I'd chose for the community.
While I have known several really well educated academics that were a hundred times smarter than I am the fact remains that the subject of ancient coins is huge and the number of school trained paid professionals available to numismatic projects pretty much guarantees that most of the coin in the ground will rot there if they wait for 'proper' academic investigation. That is why it hurts so much to see the attitude that coins would be better melted down than allowed in the hands of uneducated scum like me. Certainly there are many academics that maintain a good relationship with collectors but just try to find a scholarly journal that will publish new studies by someone who has devoted his life to that study but did not devote half a dozen years to obtaining an advanced degree. Today the advent of self publishing has allowed more books on more subjects so some of us have a chance of learning something from someone else who was merely interested in the subject. I'm a bit glad I know nothing worth publishing since I suspect it is more frustrating to know truth and not be believed than it is to seek it and not be able to find it published as of yet.
