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<p>[QUOTE=&quot;John Burgess, post: 4848472, member: 105098&quot;]Imagine if you will a zinc planchet raw about to be plated with copper.</p><p>This planchet has to be clean, clean clean, or the plating won&#039;t stick completely.</p><p>If there is zinc dust on the planchet when the plating is applied a small pocket of air is formed between the plating and the zinc planchet where the plating couldn&#039;t adhere properly. The Blisters form during the strike when expanding gas pushes up the copper plating from heat and pressure forming a &quot;bubble&quot; or &quot;balooning effect&quot;. They can manifest in a round blister, and also linear plating blisters. During the strike, the the gas from the compressed air/decompressed air around the imperfection pocket under the copper plating has to go somewhere as it expands.[/QUOTE]</p><p><br /></p>

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