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<p>[QUOTE=&quot;Info Sponge, post: 772888, member: 20538&quot;]Thank you for collecting those links: they do repay effort and study. I went and re-read them.</p><p><br /></p><p>The discussions there address my questions, but still leave me curious. For example, Sunnywood explains why some toning depends&nbsp; on the view angle and other kinds don&#039;t by attributing the difference to whether the color comes from absorption in the chemical layer versus the thin-film interference effect which he and physics-fan have described for us. But if I understand right the interference effect is supposed to be the most important one typically, and it does depend on angle of view, so shouldn&#039;t most toning be iridescent?</p><p><br /></p><p>Rob790 explains how work hardening affects reaction rates, and says that dipping chemicals inhibit natural toning. But how? There&#039;s also been a tantalizing reference to how different acid baths at the Mint correspond to different varieties of toning in the coins, which sounds like it might be the same phenomenon as the result of dipping (or overdipping as you point out). What is the key difference about an acid-washed surface that makes it tone differently?</p><p><br /></p><p>(Am I going into more depth than anyone cares about? I don&#039;t mean to derail the discussion but really am curious.)[/QUOTE]</p><p><br /></p>

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