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<p>[QUOTE=&quot;lrbguy, post: 2876806, member: 88829&quot;]You guys would do well to learn about the formation of patina as we find it on our coins, specifically bronze.&nbsp; Patina is not a mere coloration.&nbsp; Nor is it an encrustation, i.e adhesion that builds up, although it does form a &quot;crust&quot; encasing the coin.&nbsp; Patination (formation of patina) is the conversion of the metallic coin surface into a layer of a non-metallic chemical salt of the coin metal itself.&nbsp; Patina builds from the outermost surface DOWN into the fabric of the coin. What this means is that removing adhesions above the surface level of the coin is simply cleaning.&nbsp; But removal of material below the surface level is a removal of some of the original coin surface itself, and that is an irreparable alteration of the original coin, no matter how nicely it &quot;presents.&quot;&nbsp; If &quot;smoothing&quot; only takes place above the original surface, it is not an alteration of the coin, merely its appearance.&nbsp; But if &quot;smoothing&quot; dips into the surface level to &quot;even things up&quot; it is an intentional alteration of the original coin and should be described with the coin.</p><p><br /></p><p>Let your definitions come from the physical principles involved, and not from your &quot;feelings.&quot;[/QUOTE]</p><p><br /></p>

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