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<p>[QUOTE=&quot;BadThad, post: 3837036, member: 17261&quot;]You did the RIGHT thing by using distilled water. That&#039;s always the safest and first thing to try in any conservation project! </p><p><br /></p><p>Luckily, this is technically a surface contamination issue since Morgans contain no iron. That said, it is still likely to have permanently stained the coins even if the residue is removed. Another thing to consider is that residue is surely not all iron and iron oxide, there&#039;s bound to also be calcium and magnesium and traces of other common metals in it.</p><p><br /></p><p>There are a couple of routes you can take with rust. The easiest and cheapest would probably be to add a VERY TINY bit of lye to your distilled water soaking with ultrasound. These coins are technically &quot;goners&quot;, I wouldn&#039;t be concerned with using an ultrasonic cleaner at all.</p><p><br /></p><p>If the lye (alkaline solution) fails to give good results, you could also add a tiny bit of EDTA (tetrasodium) into the solution. Although I&#039;m not sure where a consumer could obtain it. EDTA in an alkaline (lye) solution will remove that surface rust for sure but overexposure will hurt the coin surface. I would keep a close eye on the whole process.</p><p><br /></p><p>As far as acetone, as you discovered, it&#039;s completely ineffective against non-organic residues. You have metal and metallic oxide residue. Organic solvents will be completely ineffective at treating this problem. </p><p><br /></p><p>GOOD LUCK![/QUOTE]</p><p><br /></p>

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