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<p>[QUOTE=&quot;BadThad, post: 3257812, member: 17261&quot;]Proofs are struck at greater pressures on pre-polished planchets with fresh, highly polished dies. That process tended to smooth out the surfaces more than a business strike. As I recall, the planchets were exactly the same, they simply added an extra polishing step for the proofs. Therefore, the amount of gas inside the clad layer would have been essentially the same for proofs and business strikes.</p><p><br /></p><p>OK....down to it.... <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie1" alt=":)" unselectable="on" unselectable="on" /></p><p><br /></p><p>The wavy lines found in proofs are from the underlying gas AND from a soft zinc core with minor imperfections on the surfaces (they can&#039;t polish the zinc core). These simply manifest themselves differently - more smoothly - on proofs due to the above.</p><p><br /></p><p>As to why the bubbles exist? I have some boring technical theories involving impurities, galvanic corrosion and water in the core.[/QUOTE]</p><p><br /></p>

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