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<p>[QUOTE=&quot;Colonialjohn, post: 2131053, member: 57741&quot;]Excellent!</p><p>Read &quot;Micro-Raman Characteristics of Silver Corrosion Products: Instrumental Set-Up and Reference Database by Irene Martina. It can be googled.</p><p>As a few commenters have noticed the spots can appear in the PMD arena after leaving the Mint. Its not so much the acid wash but probably the type of preservative they are putting on at the end of the process. An anti-oxidant coating on the blanks prior to striking or after? Being government (i.e., paperwork - lethargic political machine) and processes taking some time to change they may be using the same type of chemfilm as possibly in the 95%Ag alloys lines?</p><p>It&#039;s interesting when you look at Martina there are several MORE white compounds in the world of Ag, Cl &amp; S. Namely silver(I) Sulfite: Ag2SO3 and silver(I)Nitrate: AgNO3.</p><p>Silver at this purity as you know as with any other coin will pickup chlorine, oxygen and sulfur. The SEM/EDS analyzer confirmed silver(I) Chloride: AgCL but I suspect maybe these others should also be checked being ALSO white powder forms of silver compounds.</p><p>As you already know this being a surface phenomenon based on the above using probably an inadequate silver surface anti-oxidant (i.e., similar to why steel is dipped in chromium baths - &lt;BG&gt;; did this myself many years ago to prevent surface corrosion) so to this requires some changes.</p><p>It may not be totally corrected since a pilot study here may take time but if they continue to make this pure silver alloy for bullion type accumulators it may be possible in a long term pilot study?</p><p>This PCGS question ... it could be like carbon spots on copper proofs. My current cleaning product is strictly for copper verdigris compounds based on fluorocarbon technology (i.e., Original Coin Care) and is for green verdigris with no copper patina change. There is no point answering what can remove these three silver compounds- maybe its just AgCl? Under 5X is there visual surface depressions after removal? &lt;BG&gt;. </p><p>As you said ... they just need time ... remember in high urban areas it could be silver sulfite ... in the rural areas predominantly AgCl? Although my studies always show both chlorine and sulfur.</p><p><br /></p><p>John Lorenzo</p><p>Numismatist</p><p>United States[/QUOTE]</p><p><br /></p>

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