Confusion About What The Definition Of "Cleaning" Is...

Interseting read and food for thought.

Very complicated subject, and much to do with semantics. I think most collectors use the word "cleaned" to mean the fairly severe alteration of a coin's surface using some process or device to improve the appearance. I think "dipping" is usually felt to be a related but different and less severe process. Dipping does, in fact, alter a coin's surface, not just its toning - the process removes a tiny skin of oxidation that was once part of the coin's original composition. It is, however, generally accepted unless done too often ('dipped-out"). I do not think the use of acetone or vegetable oils and swabs on coins to be "cleaning" in the usual sense, but rather "conservation."

Let us be clear that any tarnish at all has bonded chemically with the silver atoms at the surface----I have read the complicated chemical studies and explanations of chemical removal of tarnish----some chemicals can replace the silver atoms but the surface has been disturbed. So-----any tarnish is bad news.

"Cleaning", in the negative sense, is anything which chemically alters the surface or physically removes metal from the coin. Tarnish is a form of corrosion, and cannot be removed without chemically altering the surface. Tarnish removal, whether it is by "dipping" in sulfuric-acid/thiourea solution, or "polishing" with an abrasive, or "electrochemical reaction" (the old baking-soda-and-aluminium foil technique) or whatever, is therefore "bad cleaning" and should adversely affect the value. The reason most coin collectors actually do prefer to collect (and will pay a premium for) tarnished versus un-tarnished coins is they know that the vast majority of old silver coins have indeed been "polished up" by well-meaning but ignorant previous owners; never-been-cleaned coins are therefore "rare".

There is such a thing as "good cleaning". This is using things like water or acetone to remove things such as dirt, oil, paint, glue and other foreign matter from the surface of the coin. No-one should have any ethical concerns about performing such "cleaning" - call it "conservation" if you wish to avoid the negative connotations of the word "cleaning". "Good cleaning" can still result in a coin that "looks cleaned", however: if a strip of stickytape has sat on a coin for several decades, removing the tape residue with solvent will probably show a shiny silver surface underneath - the tape has protected it - while the portions of the coin not covered with tape are tarnished in the usual fashion. You end up with a coin with a very unappealing "white stripe". Likewise, using acetone to remove PVC goo is "good", but if the goo's been there long enough, the surface is going to be crazed and pitted from the acids in the goo.

The difference is: the "good cleaning" has revealed the flaws and defects that were already there on the coin before the cleaning began, just hidden. "Bad cleaning" actually creates the flaws.

Then there is what I would consider "inevitable cleaning" - cleaning which would probably be considered "bad" in the sense that it creates an undeniably "cleaned coin", but is nevertheless necessary. A coin dug up after being underground for several centuries, especially an old copper or bronze coin, will need harsh cleaning of some kind and it will "look cleaned" afterwards - but if the alternative is a corroded, unidentifiable lump of metal slowly turning back into the piece of copper ore from whence it came, then the cleaning done to it was "necessary".

I have found that a coin (or any other silver object, for that matter) that has been dipped will tend to re-tarnish faster (and often uglier) than a mint-fresh never-dipped coin. I assume it's because the acids, after stripping away the silver sulfide, leave the surface "activated" and thus more prone to chemical reaction.

Which leads to the other major problem with dipping: it's kind of like smoking. While "just dipping once" may not do a great deal of noticeable harm, it becomes "addictive" as the coin quickly acquires an ugly re-tarnish and you'll soon want to dip the coin again... and again... until the cumulative effect becomes obvious to everyone.

I see for "good cleaning" water and acetone seem to be acceptable, has any one ever tried ultrasonic cleaning and what would this fall under,good or bad

Ultrasonics are "good in theory, potentially very bad in application". The problem is that whatever method you use to suspend the coin in the bath solution is going to cause friction when the ultrasonics are turned on. A plastic rack, a metal rack, a piece of string, a microfibre cloth, the bare base of the bath - all of these things are not good things when rubbed back and forth on the surface of a coin - which is what ultrasonics will make it do.