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<p>[QUOTE=&quot;desertgem, post: 424072, member: 15199&quot;]Ok, I agree ~ don&#039;t use a brush on pure (99.99) gold coins as the Vickers Hardness scale for pure gold is 20-25 Vickers and Keratin is&nbsp; 10-25 ( depending on the helix junctions to make fingernails or hair), so it is possible for the high end of keratin ( like a fingernail ) to scratch a Kugerand.</p><p><br /></p><p>However, for coinage gold of 90%, about 22 kt. has a vickers hardness of 75-80, higher than the keratin range. Coinage silver is higher also.</p><p><br /></p><p>The Mohs system of hardness was based on comparative hardness, what can visually scratch what. It certainly wasn&#039;t intended to deal with 4 millionths of an inch thickness.</p><p><br /></p><p>Hair with its cylindrical hollow structure and looser binding molecules allow more flexibility and doesn&#039;t have the &quot;scratch&quot; potential unless it is molecularly glued together as is the keratin in fingernails. If you ground hair against gold like a cloth, then it is very possible to scratch. </p><p><br /></p><p>With common sense, the use of a sable brush against your skin would not produce a scratch, use a fingernail clipping and blood may flow. We know that &quot;cabinet rub &quot; occurs from coins moving on lining made of plant fibers like cotton, yet people still recommend using cotton gloves to handle coins. We wouldn&#039;t recommend rubbing th e coins with the cotton gloves.</p><p><br /></p><p>I don&#039;t use a brush...just don&#039;t see a problem if others want to use it. </p><p><br /></p><p>Jim[/QUOTE]</p><p><br /></p>

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