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<p>[QUOTE=&quot;V. Kurt Bellman, post: 2125966, member: 71723&quot;]You have found the right base formula. But the assumption that because thiourea can <b><i>also </i></b>be used in recovering metal from ore it will move in this case, is false. What thiourea does is break chemical bonds with actually a wide variety of possible silver partners. Whether it moves depends on whatever else is going on. Typically moving the silver requires extraordinarily low pH, some applied voltage, and Fe ions to facilitate the reaction. Various acids have a wide range of silver reactivity, from highly so for nitric, to less for hydrochloric and sulfuric, to essentially none for citric. This is virtually the same error in methodology committed by the EPA when it initially made silver a monitored pollutant in municipal waste water streams. They overstated environmental silver&#039;s bioavailability by a factor of 10^8. I was instrumental in the first state to &quot;push back&quot; against the EPA and we won, causing all 50 states to roll back silver waste water regulations.</p><p><br /></p><p>I have changed the formula by using distilled water, to eliminate natural Fe-containing hard water, kept the pH above 3.5, and use only glass containers to avoid introducing any stray charges. Yes, the reaction is slow. I have &quot;dipped&quot; a cameo proof and several MS coins in this for 5 hours and gotten them slabbed and graded by the &quot;big 2&quot;. Oh, I also dilute all from the S-10 basic formula.</p><p><br /></p><p>I have had one notable failure. I got, dirt cheap, a 1953 Franklin proof with a half-inch wide deep purple swath right across it from 10 o&#039;clock to 4 o&#039;clock. I had never seen anything like it. It looked like a piece of VHS tape had been dipped in purple ink and laid across the coin. It spent 30 minutes in this stuff, and while the color is gone, a barely perceptible haze of mirror surface break was left behind. I still consider it a vast improvement.[/QUOTE]</p><p><br /></p>

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