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Proof of principle: removing iron oxides from silver coins
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<p>[QUOTE="Roerbakmix, post: 7469074, member: 100731"]I echo the responses given above: HCl (or any acid) will dissolve not only the deposits, but also the coin. Cleaning silver coins is much easier than bronze, in my opinion, as (especially with coins of high purity), one does not have to worry too much about the effect of the chemicals on the coin itself.</p><p><br /></p><p><br /></p><p>Indeed, this coin served as a proof of principle. I learned at least two things that will save me from experimenting with more valuable coins (both in monetary and historic sense)</p><p>1) the chloride of HCl will indeed react with the silver, but only to a limited extend: a thin layer of AgCl (also known as horn silver) forms, covering the entire coin, (which actually is a rather pleasing dull-grey patina).</p><p>2) this thin layer, though easily removed with sodium thiosulphate as described above, hinders the removal of the iron deposits: the thin layer that covers the coin will also cover these deposits, protecting them from the acid</p><p><br /></p><p>With more valuable specimens, especially when most of the coin is just fine apart from some minor deposits, I will use a precision pipette:</p><p><img src="https://www.lvl-technologies.com/files/inhalte/Geraete/Handpipette.png" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></p><p>I've worked with those handy pipettes during lab internships, and they might be quite useful for this purpose. I'm still looking for a trinoculair low-magnifying microscope (trinocular so I could share real-time video imaging on the forum - will be fun <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie1" alt=":)" unselectable="on" unselectable="on" />).</p><p><br /></p><p><br /></p><p>I have some experience in the lab, but mostly biochemical, with focus on the bio and less on the chemical. Coin cleaning is fun and can be rewarding, by increasing the value of the coin and the appeal. It's just another aspect of the hobby I enjoy![/QUOTE]</p><p><br /></p>
[QUOTE="Roerbakmix, post: 7469074, member: 100731"]I echo the responses given above: HCl (or any acid) will dissolve not only the deposits, but also the coin. Cleaning silver coins is much easier than bronze, in my opinion, as (especially with coins of high purity), one does not have to worry too much about the effect of the chemicals on the coin itself. Indeed, this coin served as a proof of principle. I learned at least two things that will save me from experimenting with more valuable coins (both in monetary and historic sense) 1) the chloride of HCl will indeed react with the silver, but only to a limited extend: a thin layer of AgCl (also known as horn silver) forms, covering the entire coin, (which actually is a rather pleasing dull-grey patina). 2) this thin layer, though easily removed with sodium thiosulphate as described above, hinders the removal of the iron deposits: the thin layer that covers the coin will also cover these deposits, protecting them from the acid With more valuable specimens, especially when most of the coin is just fine apart from some minor deposits, I will use a precision pipette: [IMG]https://www.lvl-technologies.com/files/inhalte/Geraete/Handpipette.png[/IMG] I've worked with those handy pipettes during lab internships, and they might be quite useful for this purpose. I'm still looking for a trinoculair low-magnifying microscope (trinocular so I could share real-time video imaging on the forum - will be fun :)). I have some experience in the lab, but mostly biochemical, with focus on the bio and less on the chemical. Coin cleaning is fun and can be rewarding, by increasing the value of the coin and the appeal. It's just another aspect of the hobby I enjoy![/QUOTE]
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Proof of principle: removing iron oxides from silver coins
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