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<p>[QUOTE=&quot;Sunbird, post: 7603677, member: 116324&quot;]What are the rules or principles for when object A will scratch object B? It can&#039;t be random, and it&#039;s not going to always happen, so it must be predictable in advance. I assume the sharpness is a factor, the amount of force/pressure, etc?</p><p><br /></p><p>A lot of times &quot;scratches&quot; are actually deposits made by the applied object, because it was too soft relative to the object it was trying to scratch, so it got abraded instead. Kind of like how when Chuck Norris does push-ups, he doesn&#039;t push himself up – he pushes the earth away...[/QUOTE]</p><p><br /></p>

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