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<p>[QUOTE="desertgem, post: 981083, member: 15199"]Yes, I know that Science doesn't always know the correct answer, but 2 articles ( can be googled and read, but not copied/quoted) shows 2 <span style="color: SeaGreen"><span style="color: Red"><b>possible</b></span> </span>problems for the use of Thiourea-acid cleaning solutions. Take them for what you think they are worth. Both are from peer qualified specialty journals in metals.</p><p><br /></p><p>1. Thiourea bonds more closely to silver than previously though. Casual washing with water doesn't remove the full complex which can (2) later form bonds with sulfur enhancing tarnish, and has caused spotting on silver Daguerreotypes cleaned with it, after a decade or more and IMO, there is no reason it couldn't occur on silver coins so treated as they are not generally covered with wax or polish material like silverware.</p><p><br /></p><p>My conclusions would be if one wishes to use it, use it at a diluted solution ( like 1 part EZEST, 9 parts water), and repeat until you have the amount of cleaning you want or you ruin it. The process will be slower, but you are much less likely to overshoot than using the full strength solution.</p><p><br /></p><p>Rinse extremely well with water. The article didn't give specific times, as I assume it would differ due to the solution used and the amount of toning/tarnish/corrosion already there. IMO,</p><p><br /></p><p>Jim[/QUOTE]</p><p><br /></p>
[QUOTE="desertgem, post: 981083, member: 15199"]Yes, I know that Science doesn't always know the correct answer, but 2 articles ( can be googled and read, but not copied/quoted) shows 2 [COLOR=SeaGreen][COLOR=Red][B]possible[/B][/COLOR] [/COLOR]problems for the use of Thiourea-acid cleaning solutions. Take them for what you think they are worth. Both are from peer qualified specialty journals in metals. 1. Thiourea bonds more closely to silver than previously though. Casual washing with water doesn't remove the full complex which can (2) later form bonds with sulfur enhancing tarnish, and has caused spotting on silver Daguerreotypes cleaned with it, after a decade or more and IMO, there is no reason it couldn't occur on silver coins so treated as they are not generally covered with wax or polish material like silverware. My conclusions would be if one wishes to use it, use it at a diluted solution ( like 1 part EZEST, 9 parts water), and repeat until you have the amount of cleaning you want or you ruin it. The process will be slower, but you are much less likely to overshoot than using the full strength solution. Rinse extremely well with water. The article didn't give specific times, as I assume it would differ due to the solution used and the amount of toning/tarnish/corrosion already there. IMO, Jim[/QUOTE]
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