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<p>[QUOTE=&quot;desertgem, post: 774205, member: 15199&quot;]<p style="text-align: left"><span style="color: #000000"></span></p> <p style="text-align: left"><span style="color: #000000"><br /></span></p> <p style="text-align: left"><span style="color: #000000">Unless a person actually knew exactly what the varnish/shellac/lacquer actual was, there is no good answer. Luckily, chemicals that can remove all but the most modern coatings ( similar to epoxy), are not very hazardous to metals. From alcohol to the various organics. I did a thread on using DMSO on a coating that resisted xylene, but although it did have some good effect, these coating can get into microscopic crevices and flow lines and not just soak out, one would have to use mechanical action and that damages the coin.</span></p> <p style="text-align: left"><span style="color: #000000"><br /></span></p> <p style="text-align: left"><span style="color: #000000">The chemical bonds formed makes such a coating similar to mined metals, and sound waves haven&#039;t been used for instance to break gold or gems from material such as quartz. I have tried a commercial &quot;ultrasonic cleaner&quot; but it is useless for such removal and usually has a greater affinity for damaging the coin through friction.Maybe someday someone can use a war surplus sonar or &quot;killer sonic disruptor&quot; on a coin <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie1" alt=":)" unselectable="on" unselectable="on" /></span></p> <p style="text-align: left"><span style="color: #000000"><br /></span></p> <p style="text-align: left"><span style="color: #000000">And to answer your other question about the electrolysis processes, theoretically, they can remove certain compounds, but they are all described so haphazardly. There is little repeatibility and protection for the coin itself.&nbsp; In the process you describe, without electricity, the aluminum foil and the baking soda would be the ingredients that affect the removal vs. damage. Theoretically, calculations should be done to estimate the quantity of each needed for treatment and then reduce that for a safety&nbsp; factor, rather than just tossing in a half a teaspoon and using a &quot;piece&quot; of foil. Those who use electrical sources usually just watch it doesn&#039;t smoke and melt, or watch bubbles. I recognize it use for ancients that have more corrosion ( patina) than&nbsp; coin metal itself or have had the &quot;desert patina&quot; so thick the coin is not attributable, but not for moderns. All above IMO.</span></p> <p style="text-align: left"><span style="color: #000000"><br /></span></p> <p style="text-align: left"><span style="color: #000000">Jim</span></p> <p style="text-align: left"><span style="color: #000000"><br /></span></p><p>[/QUOTE]</p><p><br /></p>

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