GDJMP: Where did you get those stats? I find it hard to believe 80% of coins, whether they're modern or classic, have been cleaned. Every coin collector I know has had it drummed into their heads, "don't clean a coin". I've been collecting since I've was a kid and I wouldn't dream of dipping a coin myself. A local dealer, who's had years of experience, will do it, but even he warns that it could come out wrong.
Actually @GDJMP may be a little low; but 80% is definitely close. Some dealers I know "prepare" every coin (CLEAN THEM) in some way before sending them to be graded. As for you, and everyone else that lacks experience cleaning coins, it is best to do as you do and don't touch them. Even an application of acetone can put hairlines on a coin if you don't know what you are doing.
BS ALERT! I am on this " expert's" ignore list. Hope someone he can "see" also refutes his opinion. OMG...Absolutely 100% and misinformed post. Cleaning, whizzing, etc. was at it's zenith during "his" time period and is still the rage. Since cleaning is going out of style (BS) I guess the fact that the four major TPGS's clean coins for a fee (ICG does not charge for the service) proves (?) collectors/dealers don't support cleaning. Brian S. teaches an ANA course on coin conservation, and most of the folks I know clean them to. I LOVE TO CLEAN COINS and do it every day! BTW, even rainbow toned coins can be made more attractive with a little conservation! What?
I still believe that the odds of cleaning a coin (again, I don't count acetone) correctly are against the average collector. We just had a State Fair that lasted for 10 days and our Coin Club had several displays. The number one question was, "the coins look so nice, how did you clean them?" The average person and beginning collector needs to be educated. I still go by the mantra "don't clean!". Apparently some members of this forum think that everyone has the same skill sets that they do and give advice that can cost a new or uninformed collector a lot of money. If you really think cleaning will help your coin, ask a trusted local coin store owner for their opinion. I did this and he, as a customer service will dip a coin for me at no cost, he has over 50 years experience doing this and still warns that things can go wrong. If you don't have a local then there's always the TPGS "Conservation" service.
Some members of this forum know that there are different "skill levels" for everything. So as I already posted: @TheMont has given all of us, who are not skilled, some great advice which I'll paraphrase - Don't clean your coins if you are ignorant of the proper techniques.
I have seen many a coin that look great with Gunk in the letters, Around the profile. I think that Daves, IHC is testament to that. Doctors should be removed from the equation. But, AS, much as I know, They are only Practicing!
Well, detecting improper cleaning can be difficult and even the TPGS missed all types of altered surfaces at first. Once you know what to look for the task becomes easy. Looking at pictures on CT is not the best way to learn. You'll need to see actual coins.
I've recently gotten interested in restoring old silver, silver plate, aluminum and copper kitchenware. I'm currently working on a beautiful Rogers silver tray and coffee set. I've been trolling various silver and metal forums looking for the best/safest way to clean the various metals--and nearly every answer I've gotten has started with the words "and that's what my husband uses to clean his coins." I was starting to wonder if I was the only one to never clean my coins.....
Where did I get those numbers ? Experience. It's no secret, anybody, change that - everybody - that knows coins, knows it. How do they know it ? Well, to a large degree because they've done it themselves their entire lives. But there is another way to know it, all you have to do is look at a coin and think, use your head. It's called deductive reasoning. You see there is this very simple fact - all coins tone, period end of story, all coins tone. So if you are looking at an older coin, and that coin is not toned, then you know, absolutely know, that coin has been dipped. Now can there be exceptions to this rule ? Yes of course there can. But exceptions do not disprove the rule, they are merely exceptions to it. And as is always the case, exceptions are far, far, fewer in number than the rule. Thus knowledgeable people KNOW that 80%, or more, of all older coins have been dipped. And he is quite correct. And anybody and everybody who knows coins, knows that. Dipping a coin is always a crap shoot - always. But with knowledge and experience it can be and is done successfully - every single day. What you are failing to take into account is another very simple fact. That being that at some point in their lives just about every coin out there has at one time or another gone through the hands of a knowledgeable dealer or collector. And usually through the hands of several of them. And these people know how to dip coins, and they DO dip coins, every single day.