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My Understanding (Flawed?) of Cleaning a Coin by Dipping
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<p>[QUOTE="-jeffB, post: 1384302, member: 27832"]Tarnish (toning) forms when sulfur combines with silver on the surface of a coin. When you dip the coin, it removes both -- the sulfur, and the silver that was chemically combined with it.</p><p><br /></p><p>Doug indicates that the dip will also remove uncombined silver. I'm a little fuzzy on that, based on a quick skim of a relevant section in <i>Coin Chemistry</i>; it seems reasonable, but it also seems reasonable that an agent could attack silver sulfide <i>without</i> attacking the silver. It'll be easy enough to check -- take a lustrous coin without toning, let it soak in dip for a while, and see what you get (comparing appearance and/or weight). I just haven't been able to bring myself to do that to a lustrous silver coin, because I'm pretty sure Doug's right.</p><p><br /></p><p>I've wondered about using low-pressure hydrogen plasma to remove the sulfur and leave the silver behind, but (a) the hydrogen might adsorb on the metal, damaging its finish, (b) the reduced silver might not look anything like the original finish, and (c) I don't want to blow up my garage.[/QUOTE]</p><p><br /></p>
[QUOTE="-jeffB, post: 1384302, member: 27832"]Tarnish (toning) forms when sulfur combines with silver on the surface of a coin. When you dip the coin, it removes both -- the sulfur, and the silver that was chemically combined with it. Doug indicates that the dip will also remove uncombined silver. I'm a little fuzzy on that, based on a quick skim of a relevant section in [I]Coin Chemistry[/I]; it seems reasonable, but it also seems reasonable that an agent could attack silver sulfide [I]without[/I] attacking the silver. It'll be easy enough to check -- take a lustrous coin without toning, let it soak in dip for a while, and see what you get (comparing appearance and/or weight). I just haven't been able to bring myself to do that to a lustrous silver coin, because I'm pretty sure Doug's right. I've wondered about using low-pressure hydrogen plasma to remove the sulfur and leave the silver behind, but (a) the hydrogen might adsorb on the metal, damaging its finish, (b) the reduced silver might not look anything like the original finish, and (c) I don't want to blow up my garage.[/QUOTE]
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