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<p>[QUOTE=&quot;V. Kurt Bellman, post: 2116682, member: 71723&quot;]I don&#039;t intentionally create AT coins. I don&#039;t mostly like deeply toned coins, nor do I like blast white usually. There is a &quot;normal for its age&quot; tone that is easier to recognize than it is to describe. I have accidentally created several AT coins, and then reversed them to bring them back closer to normal. Then I have done controlled experiments to confirm how to it on demand, and I was able to, but not with 100% success. There are factors involved that I still don&#039;t understand. Perhaps it&#039;s trace contaminants on a particular coin. I am working on producing a video/Keynote presentation showing the entire process. The difficult part is photographs in the oven.</p><p><br /></p><p>The process IS fully reversible, because it is itself is a reversal of the TRULY ESSENTIAL process of coin dipping, not the one using any commercial product or anything in Weimar&#039;s book. It turns out that thiourea is the key item, not the acid. Any acid can be used, even citric acid like that used in foods. When thiourea is in an acidic solution, it removes sulfides of silver from a coin. When it is in an alkali solution, it DEPOSITS sulfides on surface silver. I gave a Money Talks presentation on this at ANA Chicago 2014. I can&#039;t help it if you weren&#039;t there and the numismatic press didn&#039;t cover it. CoinWeek will eventually have it available on DVD. There are NUMEROUS chemicals used in old-school black&amp;white photography that can be used, either as intended or by diluting them, that can be used to AT silver coins. But there&#039;s more. Since copper is on the same column in the Periodic Table as silver is, some of the reactions have effects on cents, clads, and nickels, too.</p><p><br /></p><p>But yes, there is still a need for a much closer look at the process WHILE IT IS HAPPENING, and I&#039;m working on precisely that.[/QUOTE]</p><p><br /></p>

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