2 Decent Barber dimes one a 1904s that is totally black and the other a 1899 which is partially black on the obv........Question is what causes a coin to turn black? The 04s looks good despite being black but the 99 looks bad with 3/4 normal color and 1/4 black. I would supose that this can not be removed. What do ya think???
lake: I really like Barbers, and collect all series. As for the 1899, it appears that it may have been buried at some time int eh past. It may clean up with a dip or you may try acetone, soak and rinse. I'm not sure, but I think that the acetone is the way to go. Just follow the directions that some have given in another link recently. As for the 1904S, nice condition for a very scarce coin. Silver will naturally turn darker over time. That is the nature of the metal. 99.99% of old silver coins that you see that are bright white have been dipped to remove the toning. It can be caused by many factors, mostly environmental, for example, those old brown coin envelopes, that have sulphur (spelled wrong).
I have some silver dimes which were stored in a Wayte Raymond "Popular" coin album since 1953 by my grandmother. The reverses next to the paper were mostly black.
There are several things that may have caused this. As bone mentioned, fire may cause this. Also, dipping a coin and not properly neutralizing it can cause black spots. Many other chemicals, particularly oxidizers can also turn a coin black. The coin on the right appears to be heavily corroded, and in my opinion there is most likely nothing you can do to improve it's appearance. As for the one on the left, I suspect the only thing that would remove the black spot would be dip, but I would recommend leaving it alone, as would quite possibly just make the appearance worse.
Because there are two acceptable spellings of the word, sulphur & sulfur, and this spell checker is only using 1 of them.