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<p>[QUOTE=&quot;Oldhoopster, post: 4634703, member: 84179&quot;][USER=24314]@Insider[/USER] I think the lamination is a red herring for the following reasons.</p><p><br /></p><p>The lamination cuts perpendicular across the discolored areas.&nbsp; I would expect that the lamination would follow the boundaries of the poorly mixed regions.&nbsp; If the regions have different ductility or hardness due to composition variation, they may not bond well as the ingot is rolled and elongated.&nbsp; This could result in weakness or lack of bonding between the regions along the boundaries.&nbsp; No issues there.&nbsp; But the lamination on this coin crosses multiple discolored regions.&nbsp; That doesn&#039;t make sense. And if the regions have a similar hardness, then they would be bonded with the other metal grains, so there wouldn&#039;t be a lamination.</p><p><br /></p><p>If the lamination is caused by a gas bubble or void, once again, I wouldn&#039;t expect it to cross through regions of differing compositions. Some reasons for poor mixing may be due to an area being hotter or colder than the bulk material.&nbsp; This could result in different viscosities within the melt. Also, It would not be unusual for regions of differing compositions to have different viscosities as they melt. How would a bubble cut across regions that have varying viscosities?&nbsp; It can&#039;t. The bubble would stay in the most fluid region</p><p><br /></p><p>Now if the marks were just stains left by a dirty roller and toned at different rates over the years, a lamination could easily cut across them because it was already in the ingot before rolling.</p><p><br /></p><p>I&#039;m not a metallurgist and don&#039;t claim the comments in my last 2 posts offer definitive proof, but IMO, there are too many things that don&#039;t line up to make me believe it&#039;s an improperly mixed alloy.&nbsp;&nbsp; I believe the discoloration is a stain left by dirty rollers.[/QUOTE]</p><p><br /></p>

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