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<p>[QUOTE=&quot;Insider, post: 2902765, member: 24314&quot;]IBetASilverDollar, posted:&nbsp; &quot;Let&#039;s say with Silver...my understanding was once it becomes completely black that the next step in the process is damage to the coin, is that not the case and reality is it&#039;s just permanently black at that point?&nbsp; If so that doesn&#039;t worry me at all and like that look like the one you posted, my main concern was buying a coin with black toning and 20 years from now the coin is damaged.&quot;</p><p><br /></p><p>Aside from the opinions here, I&#039;ll suggest you look on the internet for more info.&nbsp; IMO, GDJMSP has summed it up well.&nbsp; I&#039;ll add some things I think we all know.&nbsp; Toning is oxidation.&nbsp; Since it changes the surface of the metal, one prominent numismatist/chemist calls toning damage.&nbsp;&nbsp; In many cases it can protect a surface from further oxidation.&nbsp; When it is attractive it is called toning, when ugly tarnish.&nbsp; Toning is a cumulative process and the colors often change as it progresses.&nbsp; In most cases, the darker the toning, the more <b>corroded</b> the underlying surface will be. Black is end-stage. </p><p><br /></p><p>jeffB, posted: &quot;I&#039;ve seen a couple of older silver coins (Seated, Barber) that appear to have <i>powdery</i> black toning. I haven&#039;t tried wiping it away, but it looks like a situation where the toning layer is porous, and <i>does</i> allow further attack on the silver underneath.&quot;</p><p><br /></p><p>The black powder is a corrosion product.&nbsp; It is like soot on a surface.&nbsp; It will wipe off but that may leave a streak and often exposes a shiny black surface. </p><p><br /></p><p>GDJMSP, posted: &quot;But I think I must mention that terminal toning is in itself a somewhat subjective term. We can call it what it is because of what we see - when the toning is black it is referred to as terminal. But we don&#039;t really know, can&#039;t ever really know if it is truly terminal unless and until we remove it.&quot;</p><p><br /></p><p>I&#039;ve been playing around with terminally, black toned coins for years. Once the surface is black, the coin is corroded.&nbsp; <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie2" alt=";)" unselectable="on" unselectable="on" />[/QUOTE]</p><p><br /></p>

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