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<p>[QUOTE=&quot;Conder101, post: 2525945, member: 66&quot;]When the metal is melted there are often bubbles of trapped gases contained within it, especially with the copper/zinc alloy because copper melts at a higher temperature than zinc boils.&nbsp; Normally you will try to hold the melt at a specific temperature for awhile to give the gasses a chance to slowly rise through the melt and escape at the surface.&nbsp; If you pour too soon or agitate the melt too much you can retain trapped gas bubbles inside the ingot.&nbsp; (it is also possible to get other contaminates, pieces of slag, excess flux for the surface of the melt etc, trapped inside the ingot.)&nbsp;&nbsp; Now when you roll out the ingot where do these bubbles or other contaminates go?&nbsp; They can&#039;t be reabsorbed into the solid metal so they tend to get flattened and spread out forming a hollow layer or layers inside the strip.&nbsp; If it is close enough to the outside surface it may break through creating a lamination.&nbsp; A larger void inside that doesn&#039;t break through can result in a &quot;dumb&quot; blank that will not ring when struck.&nbsp; If the bubble or contaminate is large enough it it may spread out larger than the diameter of the blank&nbsp; This is the cause of split planchets.[/QUOTE]</p><p><br /></p>

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