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<p>[QUOTE=&quot;Info Sponge, post: 981127, member: 20538&quot;]That didn&#039;t sound right chemically, but I don&#039;t want to disagree with Doug unless I&#039;ve checked my facts carefully.</p><p><br /></p><p>Silver &quot;cleaning&quot; solutions are &quot;acidified thiourea&quot;, thiourea plus an acid. More information at <a href="http://cool.conservation-us.org/waac/wn/wn11/wn11-1/wn11-103.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://cool.conservation-us.org/waac/wn/wn11/wn11-1/wn11-103.html" rel="nofollow">http://cool.conservation-us.org/waac/wn/wn11/wn11-1/wn11-103.html</a>, though the methods they use for conserving silver artifacts would horrify a coin person.</p><p><br /></p><p>The chemistry of thiourea in an acid solution gets rid of silver sulfide, but thiourea with enough acid dissolves silver itself so well that it&#039;s a useful leaching agent for extracting silver. So dips remove silver as well as tarnish, just like Doug said.</p><p><br /></p><p>Doug&#039;s explained many times how luster comes from microscopic flow lines, and if you start dissolving silver the exposed peaks go first, so you get something that would look like normal sorta-flat metal under a microscope, but which at the macroscopic level loses the luster that collectors value highly.[/QUOTE]</p><p><br /></p>

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