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<p>[QUOTE=&quot;SPP Ottawa, post: 1520640, member: 39508&quot;]Fair enough (assuming your container of onions also is in a vacuum or all free oxygen was replaced with another gas or liquid), although I imagine a plain container of onions would turn a silver coin black because of the hydrogen sulphide (H2S) gas (which is very acidic as well). I think the general consensus here, and hence the cheap shots, is that artificial manipulation of coins is frowned upon. But, I guess once you own the coin, you are free to do whatever you want with it...</p><p><br /></p><p>I find this whole topic fascinating. Natural toning is a product of oxidation of the coin (and not a reduction reaction in an anaerobic environment). Even the seller uses the &quot;rust&quot; analogy (oxidation of ferric iron to ferrous iron). If it was truly an anaerobic environment, I would expect precipitates building up on the coin, instead of the outermost metal of the coin oxidizing. I can&#039;t help but wonder what the long term effects of rapidly colourizing these coins would be... The 1973 Canadian double dollar specimen set is a prime example of what long term damage can occur in even a mild oxidizing environment....</p><p><br /></p><p>I am tempted to buy one of these altered coins, and stick it under the SEM at work, just to see if there are, in fact, precipitates causing the colour effect, and what elements are responsible for doing so...[/QUOTE]</p><p><br /></p>

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