I’m curious…If a coin has been dipped, and it later starts to turn in the holder…if caught early enough, can it be conserved with acetone alone or does it need to be dipped in a chemical dipping solution again? Please only respond if you have actual knowledge of this process. I don’t want any guesses. And please don’t tell me the obvious (to send it in for conservation)…This is just a hypothetical question and for learning purposes only. So, that would defeat the purpose. Besides, they are pretty tight lipped regarding their procedures and would not tell me anything, anyway. Thanks.
Toning is corrosion. Acetone will have no effect, positive or negative, on corrosion. I assume what you mean by "turn in the holder" is that toning or corrosion has shown its face. Sometimes, that means that the coin was inadequately rinsed after its dip.
I’m talking about the coin developing residue from an improper rinse not from general toning or corrosion.
Acetone will not affect the toning. It needs to be dipped to remove the toning. If was given a correct dip and properly rinsed and dried then left out in the air for an hour or two it won’t tone again, unless the holder has an air leak. Dipping too long removes the coins luster. Not rinsing the coin properly is where most people make their mistake. The coin must be completely rinsed off and dried before holdering it.
@Collecting Nut I agree with almost everything you said. I just thought that residue discoloration from an Improper rinse was different than toning due to silver oxidation. Oxidation is environmental, whereas discoloration due to an improper rinse is more of a chemical reaction. Oxidation is a chemical reaction, too, of course, but a coin that is not rinsed properly can be stored in the proper environment and still turn, because of the chemical residue. That doesn’t happen normally, with coins that are rinsed properly. Most Coins that you see that are toned naturally are due to the holders, sulfur paper or humidity and temperature. Residue discoloration is a different animal. I know that acetone won’t remove natural toning, but I thought it could remove the residue, if caught early enough. Maybe I’m wrong? I don’t own a coin like that but this is just something that I’ve always wondered about.
I would think that it depends on the coin. Also, conservation on problem coins is the only kind that I would mess with. I'm just wondering what you mean by "chemical residue". I just would need to see it, in order to go any further.
Dip is generally an acid combined with thiourea. Water is better for dislodging those than acetone would be. If the coin starts to discolor after dipping, that's a further chemical reaction, producing either metal oxide (and possibly carbonate) or metal sulfide. Neither of those chemical compounds are soluble in acetone, so acetone won't do anything to remove the discoloration.
