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<p>[QUOTE=&quot;Kentucky, post: 1772474, member: 33176&quot;]Actually I did not say what you said.&nbsp; I said that a layer of silver oxide or a layer of silver sulfide would give the same appearance depending on the thickness of the layer.&nbsp; The color is caused by reflection/refraction of light that can be interfered with constructively or destructively depending on the thickness of the film.&nbsp; Why do soap bubbles show some of the rainbow toning we see on some silver coins?&nbsp; The soap material is white or transparent, so the color here is a similar phenomenon.&nbsp; Now, if we go further, either process of forming silver sulfide of silver oxide is an oxidation of the silver.&nbsp; If the silver oxide gets thicker, the coin will dull and be kind of lusterless, while if the silver sulfide gets thicker, we have more of a chance of the coin turning black as in classical tarnish.&nbsp; I try not to get too dogmatic about chemical stuff because guys that have been around coins as much as someone like Doug have actually seen a bunch of stuff it would be very hard for me to intelectuallize.&nbsp; It&#039;s like trying to instruct a chem lab using a manual where a very knowledgeable chemist has written the experiments, but obviously hasn&#039;t done them because in practice, lots of thing are quite different than theory.&nbsp; I don&#039;t know anything about the Coin Armour having never used it and haven&#039;t read the literature.[/QUOTE]</p><p><br /></p>

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