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<p>[QUOTE=&quot;Orielensis, post: 3193488, member: 96898&quot;]I have recently experimented a bit with using a 10% solution of dinatrium-ethylendiamine-tetraacetate (Na2H2EDTA), a salt of<a href="https://en.wikipedia.org/wiki/Ethylenediaminetetraacetic_acid" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Ethylenediaminetetraacetic_acid" rel="nofollow"> ethylenediaminetetraacetic acid</a> (EDTA), which is found in most soaps. EDTA is a chelating agent, i.e. it sequesters and binds metal ions into a complex. Thus, it will slowly eat away all (!) patina and encrustations which constitute metal compounds, including horn silver. It will neither react with the pure metal of the coin, nor, unfortunately, with non-metal compound encrustations such as chalk or most &quot;dirt&quot;. Compared to cleaning with strong acids, lye, electrolysis, and other scary methods, EDTA could be considered a relatively mild approach.</p><p><br /></p><p>A 10% solution in distilled water will be only slightly acidic (ph=5, about as acidic as your skin) and the substance is relatively harmless (used in most cosmetics). Therefore, you don&#039;t run the risk of poisoning your family when cleaning your coins that way...</p><p><br /></p><p><b>That said, I agree with those who posted before me, and, would only use chemical cleaning methods like this as a very last resort on otherwise hopeless cases.</b></p><p><br /></p><p>To give you an impression of both the good and the bad that EDTA can do, here are two before-and-after pictures.</p><p><br /></p><p>I acquired this Alexandrian BI tetradrachm of Philipp II very cheaply because crucial parts of the portrait were obscured by horn silver. Here is the seller&#039;s picture:</p><p>[ATTACH=full]824879[/ATTACH]</p><p><br /></p><p>After two days in EDTA, it looks like this. The horn silver is gone and the portrait now unobscured. Some copper-colored deposits remain, and though it might be possible to clean them off mechanically, I don&#039;t dare to do so. The EDTA also stripped the coin of all the rather pleasant darkish patina (silver sulfide?) and exposed previously hidden surface problems:</p><p>[ATTACH=full]824880[/ATTACH]</p><p><br /></p><p>Did my cleaning improve or ruin the coin? You decide, I guess.[/QUOTE]</p><p><br /></p>

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