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<p>[QUOTE=&quot;Midas, post: 120268, member: 2761&quot;]Copper is a VERY reactive metal.&nbsp; Oxygen causes it to &quot;tone&quot; quickly as well as many other chemicals.&nbsp; Sulphur, for instance, is found in many papers (like coin paper wrappers) and it too can cause unattractive spotting/toning on copper coins.</p><p><br /></p><p>More on sulphur spots...</p><p><br /></p><p>Carbon spots (what some collectoris call them) aren&#039;t actually carbon, When copper reacts with sulfur in some form or other, it becomes copper sulfide and the process does indeed involve oxidation.&nbsp; Hence the color change.</p><p>&nbsp;</p><p>Many coin graders and conservators agree that &quot;carbon spots&quot; are usually the result of droplets of saliva (and an occasional dandruff flake) that have landed on coins while they were being handled and talked over.&nbsp; Take a proof coin and cough on it...watch it develop spots later.&nbsp; Don&#039;t DO THAT, bit I am making a point that you should NEVER exhale over nice proof or BU copper coins.&nbsp;&nbsp; As such, it is not that we eat raw sulfur, but some foods do contain more sulfur than others.[/QUOTE]</p><p><br /></p>

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