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<p>[QUOTE=&quot;SuperDave, post: 2279539, member: 1892&quot;]Most coins look worse cleaned than they did dirty. The crud doesn&#039;t form an even layer on the coin; some areas are dirtier than others and the cleaner areas form a stronger layer of patina than the dirty ones which are better-insulated from atmospheric chemicals.</p><p><br /></p><p>Then, when you clean the dirt off, the coin has areas which appear plainly &quot;cleaner&quot; to the eye. I suspect you would like a successful conservation less than you like the coin right now.</p><p><br /></p><p>Here&#039;s how I attack a conservation like this, when I don&#039;t necessarily know what I&#039;m removing:</p><p><br /></p><p>The process starts with a shot glass large enough to contain the coin plus an extra half- or inch of liquid, but not large enough for the coin to lay flat. That way the liquid can reach both faces equally.</p><p><br /></p><p>First liquid is distilled water. I&#039;ll run the coin through two or three cycles of freezing, thawing, heating (below boiling but cook the coin for a few minutes) and then refreezing. I change the water before the heating step. That&#039;ll usually take <i>gum</i> off a coin without chemicals, much less encrusted dirt. I am absolutely against using any sort of cloth/Q-tip on any coin, ever, and this is what I&#039;ve come up with for the ones you just wish you could use soap and water on. It&#039;s is far better for plain dirt than acetone, which is an organic solvent....</p><p><br /></p><p>....good at removing what the water cycles didn&#039;t. This time, you&#039;re filling the shot glass with acetone, covering it with a small piece of glass to achieve an airtight seal, and (in my case since I don&#039;t have a garage) letting it sit overnight in front of a slightly-cracked bathroom window. This provides just a little air movement, which is all you need to safely employ quantities of acetone this small, with this procedure. Volatile as acetone is, any which manages to evaporate instantly leaves on molecular air movement (figuratively) and does not concentrate unless in perfectly still air. All of the above applies to the use of xylene, another solvent of concern as it&#039;s non-polar compared to acetone (a differentiation whose importance I&#039;ll leave the reader to learn <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie1" alt=":)" unselectable="on" unselectable="on" /> ).</p><p><br /></p><p>For a coin not known to be suffering from PVC plasticizer contamination, this one acetone soak followed by a &quot;swish&quot; in fresh acetone (I use wooden tongs, which stand up to acetone in the long run better than anything else soft enough to grab a coin with) is usually enough to remove whatever it&#039;s capable of in that specific instance.</p><p><br /></p><p>Sometimes you just have to settle for whatever a prudent level of intrusiveness is able to give you.</p><p><br /></p><p>You&#039;ll note that I didn&#039;t mention any sort of &quot;picking&quot; tool. I&#039;ve found that freezing/heating cycles can remove even thick layers of crud, and use tools rarely. When necessary, only a rose thorn will do me (I don&#039;t own a porcupine), and I work under magnification with the coin underwater to minimize scratching from any random piece the thorn might dislodge.</p><p><br /></p><p>Cleaning a coin is easy. <b>Conserving</b> a coin requires patience and respect. This is a subject of interest to me, and I&#039;m slowly preparing a website which will address these issues plainly and with the broader numismatic picture in mind.[/QUOTE]</p><p><br /></p>

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