This arises out of another thread, and I didn't want to hijack the discussion there. What was said was that a dipped coin will later turn very dark. I don't know that I'd heard that before. What is the reason that such would happen? Is it inevitable with every dipped coin? You certainly see some slabbed silver coins with MS grades that have turned quite black and sometimes even a bit dull. Should it be assumed that they must've been dipped at one time?
Coins that have been dipped will turn dark if the dip is not properly rinsed off the coin. It only stands to reason. A properly dipped AND rinsed coin will not turn dark. It'll even have some difficulty in toning if even at all.
So, if I took a circulated Kennedy half and put thin strips of tape spaced apart vertically on the obverse and then dipped it without rinsing eventually the uncovered strips will form black bars which will make it look as if Kennedy is in jail?
I wouldn't day that they "will", I would say that some might. There could be several. As mentioned, if not done correctly there may be dip residue on the coin and that could in some cases cause it, but certainly not in all of them. Dip residue can and often does show up on coins as spotty and or blotchy discoloration. In others it can show up as a dark film over most of the coin. Absolutely not. There are literally millions of dipped coins in TPG slabs, and more made every day, that have not turned dark in any way. Nope, not at all. It is completely normal and even expected that silver coins will turn dark eventually. But they do so because of toning, natural toning. All toning will eventually turn dark, and eventually black, that is the very nature of toning. As far as some looking dull, that is completely normal too. Toning, if allowed to progress unchecked, will destroy some luster on a coin, leaving them looking dull. Eventually it will destroy all luster on the coin. That is why proper storage is so important, because proper storage greatly slows down the toning. In effect, if stored properly, toning will progress so slowly that you will not its final stages in your lifetime, maybe not even in your kids lifetimes. But eventually it will happen. That is the nature of silver, and of toning.
