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<p>[QUOTE=&quot;desertgem, post: 2129740, member: 15199&quot;]The thread on milk spots made me consider the annealing of the planchets before striking. I found the statement that the SF mint now uses a process of annealing in a mixture of ~ 96% Nitrogen gas and 4% hydrogen gas at high temperatures</p><p><br /></p><p>&quot;Unlike the days of old, SF Mint annealing furnaces are environmentally friendly even as blank <span style="color: #ff0000">molecules are excited in an oxygen-starved environment </span>at temperatures ranging from 1050 degrees Fahrenheit to 1650 degrees Fahrenheit. For the technically minded, oxygen deprivation is necessary to minimize blank oxidation. The actual atmosphere within the furnace chamber is a combination of nitrogen (~96%) and hydrogen (~4%).&quot;</p><p><a href="http://www.coinnews.net/2013/04/03/u-s-mint-at-san-francisco-preparing-coin-blanks/" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.coinnews.net/2013/04/03/u-s-mint-at-san-francisco-preparing-coin-blanks/" rel="nofollow">http://www.coinnews.net/2013/04/03/u-s-mint-at-san-francisco-preparing-coin-blanks/</a></p><p><br /></p><p>My thoughts is if ammonia gas is produced ( the temperature could be sufficient), but since it appears not to be under significant pressure, I am not sure.&nbsp; My train of thought is that if some ammonia was produced, other chemicals might be used to eliminate the odor within the mint, such as sodium bicarbonate or acetic acid, [common use]producing mainly odorless ammonium salts such as ammonium acetate or ammonium bicarbonate. Ammonium bicarbonate is insoluble in acetone and alcohols, but the acetate salt is soluble in both. Thus I would suspect the bicarb more.</p><p><br /></p><p>Ok, here is my questions.</p><p><br /></p><p>1. Anyone been in the SF mint last few years that was told anything about the annealing overs that use a non-oxidative atmosphere,&nbsp; or any ammonia smells noted? </p><p><br /></p><p>2. Does the Philadelphia and WP mint use the same new ovens?</p><p><br /></p><p>3. What is the oldest .999 coin with the spots you know about?</p><p><br /></p><p>If this is a false track, the history and makeup of anti-oxidizing solutions seem to be the next area that could cause the spots. </p><p><br /></p><p>These seem to be the 2 main areas that could change recently</p><p><br /></p><p>Thanks, </p><p>Jim[/QUOTE]</p><p><br /></p>

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