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<p>[QUOTE=&quot;Roerbakmix, post: 4513479, member: 100731&quot;]I don&#039;t have an answer as to why the artificial patina suddenly disappeared, however, as someone who regularly restores ancient silver coins, I&#039;ve grown a bit wary about using the aluminium / baking soda redox-method. Most ancient coins have a (desired) Ag2S (silver sulfide) patina; the greyish silver patina. The above mentioned redox reaction (middle line, describing the Ag2S &gt;&gt; Ag and H2S) is an extremely fast reaction that can strip a coin of its desirable patina within a few seconds. </p><p><br /></p><p>In your case, where the artificial patina disappeared for an unknown reason in the relatively short time span of 4.5 months, I would have waited another 4.5 months for it to disappear entirely.[/QUOTE]</p><p><br /></p>

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