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My Understanding (Flawed?) of Cleaning a Coin by Dipping
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<p>[QUOTE="kanga, post: 1384132, member: 9270"]Okay, please poke holes in my understanding and correct me.</p><p><br /></p><p>Toning of silver coins is most often because of sulfur.</p><p>Sulfur and silver combine rather easily to form silver sulfide; that's the black we've used to seeing on silver.</p><p>When a silver dip is used to remove the toning it removes the silver sulfide.</p><p>And that's where the problem is.</p><p>Note I said "it removes the <u>silver</u> sulfide", <b>NOT </b>"it removes the sulfide".</p><p>So some of the silver at the surface of a coin is removed.</p><p>And the removed silver comes from the microscopic flow lines formed when a coin is struck.</p><p>It's those microscopic flow lines that gives a coin with original surfaces its hourglass reflectivity.</p><p>That's why a coin dulls down after being dipped.</p><p>The pros that have practiced a lot use a quick dip in a diluted solution to clean their coins.</p><p>Then a total bath in distilled water to stop the cleaning process.</p><p>Many times that was undetectable by the TPGs (or ignored in the case of many 19th century coins since a high percentage have an old cleaning that has retoned naturally).</p><p><br /></p><p>But with the new PCGS system I'm not sure that a light dip is undetectable.[/QUOTE]</p><p><br /></p>
[QUOTE="kanga, post: 1384132, member: 9270"]Okay, please poke holes in my understanding and correct me. Toning of silver coins is most often because of sulfur. Sulfur and silver combine rather easily to form silver sulfide; that's the black we've used to seeing on silver. When a silver dip is used to remove the toning it removes the silver sulfide. And that's where the problem is. Note I said "it removes the [U]silver[/U] sulfide", [B]NOT [/B]"it removes the sulfide". So some of the silver at the surface of a coin is removed. And the removed silver comes from the microscopic flow lines formed when a coin is struck. It's those microscopic flow lines that gives a coin with original surfaces its hourglass reflectivity. That's why a coin dulls down after being dipped. The pros that have practiced a lot use a quick dip in a diluted solution to clean their coins. Then a total bath in distilled water to stop the cleaning process. Many times that was undetectable by the TPGs (or ignored in the case of many 19th century coins since a high percentage have an old cleaning that has retoned naturally). But with the new PCGS system I'm not sure that a light dip is undetectable.[/QUOTE]
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