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<p>[QUOTE=&quot;Leadfoot, post: 535379, member: 2972&quot;]Thanks for sending the link, that&#039;s a wonderful site!</p><p><br /></p><p>A few points...</p><p><br /></p><p>o&nbsp; The site is addressing how to conserve copper that&#039;s been buried in the ground, not copper coins like the one shown in this thread (which doesn&#039;t look like a buried coin).&nbsp; As I&#039;m sure you&#039;re aware, buried ancient coins typically look nothing like the coin in this post, but rather have a completely encased patina like this coin (or even worse, as this coin has already been conserved):</p><p><br /></p><p><img src="http://www.pbase.com/miker/image/51196225/medium.jpg" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></p><p><br /></p><p>So therefore, the conservation methods for these coins (which typically look like a &quot;hunk of corrosion&quot;) should take that into effect, and be quite different from a coin in the condition of the OPs.</p><p><br /></p><p>o&nbsp; <i>&quot;A thin layer of copper on the coin oxidizes to form a consistent and nonconcealing layer of copper (I) oxide (cuprite) called a patina. Numismatists sometimes refer to this process as &quot;toning.&quot; This &quot;dull-looking&quot; patina usually protects the coin from further corrosion though impurities from the air, ground, and sea can cause further corrosion. A good patina should not be removed. If it is removed, the bright, newly-exposed surface will once again oxidize, causing a slight loss of the coin metal.&quot;</i>&nbsp; Part of this is correct, and part is incorrect.&nbsp; First off, not all patinas are copper oxide (BTW, copper oxide is red, not blue/green), so that part isn&#039;t entirely accurate.&nbsp; The part about patina being considered toning isn&#039;t entirely accurate either (sometimes it&#039;s toning, other times it&#039;s verdigris, and other times it&#039;s corrosion).&nbsp; That said, and this is key, the part that is correct is that the patina actually protects the surface of the coin, and once you strip this off, you&#039;ve got a very-reactive and fresh copper surface (which is why most copper specialists that dip and strip coins apply oil to the surface).</p><p><br /></p><p>o The following quote explains precisely what I suggested above:&nbsp; <i>&quot;It is important to note that the single most destructive force in causing corrosion is moisture; most of these reactions would not occur without its presence.&quot;</i>&nbsp; In other words, take away the water, and you effectively stop corrosion.&nbsp; Silica dessicant is very cheap, readily available, and non-destructive answer to stop corrosion -- and it works.</p><p><br /></p><p>o <i>&quot;The most damaging corrosion occurs when chlorides and moisture come into contact with a coin, and chlorides are unfortunately quite common in the ground.&quot;</i>&nbsp; This is a great quote, and chlorides are something I didn&#039;t mention in my original post (my oversight), but similar to sulfur, they are relatively easy to stop from getting to the coin (a kontain or airtite or even a 2x2 all do a great job of limiting airflow and thus chlorine/sulphur), and if you remove water then what little sulfur/chlorine does make its way to the surface will do little to the coin.</p><p><br /></p><p>Again, you are free to conserve your coins as you see fit, but when you jump to suggesting things that simply aren&#039;t true as a justification I will (respectfully) take issue.</p><p><br /></p><p>Take care...Mike[/QUOTE]</p><p><br /></p>

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