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<p>[QUOTE=&quot;GDJMSP, post: 1804377, member: 112&quot;]That green patina you are talking about is called many things, green patina, bronze disease, and verdigris. But plain and simple verdigris is what it is. And for verdigris to be able to form it has to destroy at least part of the metal, it literally eats into the surface of the metal. And if metal is destroyed that is corrosion. Again, plain and simple.</p><p><br /></p><p>But people call it a patina because it sounds better than calling it corrosion. Corrosion has a derogatory connotation to it, patina does not. That is because patina merely refers to a color, any color. And color does not necessarily refer to corrosion.</p><p><br /></p><p>If you remove verdigris from a coin you will always see that the underlying surface of the metal was damaged when compared to the surrounding metal not covered by the verdigris. The difference is quite obvious. </p><p><br /></p><p>The same is true with copper roofs, and it is also obvious to see if you have ever restored one, as I have. When you strip away the green (the verdigris) and you also strip away the brown (the normal color of oxidized copper) and compare one area to the other, it is quite easy to see where the verdigris damaged the underlying metal.</p><p><br /></p><p>Now the protection of both toning or a patina that you mention, yes that is true, it does form a protective layer. But that does not mean that there was no damage done by that green patina (the verdigris). That initial damage is always there. But once that patina is formed the action of it upon the metal is greatly slowed down. And it is that way that way that it offers a sort of protection.[/QUOTE]</p><p><br /></p>

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