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Message:: [QUOTE="Steve Sybesma, post: 2686015, member: 86206"]There is a problem with ultrasonics I would like to bring to your attention which is why I won't use them on a coin that has any significant numismatic value (you would have to determine what that is to you). This regards leaving them in for a LONG period of time...you will have to test to see what that is on your machine. Most have timers that go up to an hour, which is too long. Always do testing first on a coin that has little or no numismatic value. On Lincoln Cents for one, I have seen the letters for LIBERTY as well as the date receive a lot more attention from the ultrasonic action than the surrounding area. Those areas actually lost all or most of their patina in the ultrasonic process. Other impacted areas with sharp relief (especially scratched areas) also suffer similarly. So, if the coin has any sharp relief in any of its details, those areas will likely lose their patina from the ultrasonic action if left in long enough. Definitely don't use on any rare coin!!!  If the value of the coin is less than $2.00, I say use your better judgement on what you would rather have...either the value of the coin which is better if left untouched or what it looks like to you. The only solutions that I've seen which were acceptable to the numismatic associations are professional cleaning of virdigris by professionals.[/QUOTE]