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<p>[QUOTE=&quot;mrjason71, post: 2926860, member: 90347&quot;]What causes a copper coin to turn red? What causes one to turn brown? Are they caused by different chemical processes? Or is it the same process and brown has just been exposed to the necessary conditions longer? Like first yellow, red, purple, blue, brown, then black or something like that.</p><p><br /></p><p>I&#039;ve googled this one quite a bit and I always see conflicting statements (sometimes within the same article). Reading Coin Chemistry (Weimar) and even that seems a little contradictory. I believe it&#039;s saying various sulfurs in the air (hydrogen, carbonyl, and dimethyl) cause toning. It says keep your untoned copper coin AWAY from sulfur if you want it a nice red someday. Copper oxide is the nice red. Theres cupric oxide and cuprous, right? There&#039;s copper 1 and copper 2, right? One red and one is black. Is something other than sulfur making the copper red? It must be or he wouldn&#039;t say keep copper away from it. What&#039;s making the good red copper oxide? Does something other than sulfur create the good copper oxide?</p><p><br /></p><p>So as you can see, I&#039;m a jumbled mess. Seems that it&#039;s pretty well established that sulfur turns it brown. What turns it red? Well...I&#039;d like to know. I guess I could go boil and egg and find out but that would be too easy <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie2" alt=";)" unselectable="on" unselectable="on" />[/QUOTE]</p><p><br /></p>

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