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<p>[QUOTE=&quot;calcol, post: 3621462, member: 77639&quot;]True, finger tips do not have sebaceous glands (i.e. oil glands).&nbsp; But we are constantly touching parts of our body that do have them, which is any part that has hair follicles.&nbsp; So the tips are picking up oil from the backs of the hands and fingers as well as from the arms and other areas. </p><p><br /></p><p>The fingerprints we leave behind are a complex brew of chemicals consisting of salts, oils, and dead epidermal cells (proteins and nucleic acids).&nbsp; That&#039;s why a wide variety of detection methods can be used.&nbsp; For example, ninhydrin spray reacts with proteins to produce colors, and dust techniques rely on dust particles sticking to oils.</p><p><br /></p><p>On coins, the chemicals in fingerprints may directly react with metal making the print visible.&nbsp; However, it&#039;s also possible that the chemicals accelerate the reaction of hydrogen sulfide gas (the main cause of toning) with metal to make the fingerprint visible.</p><p><br /></p><p>BTW, there have been rare coins with obvious fingerprints that have been certified and sold for 4 or 5 figures.&nbsp; Want an example?&nbsp;&nbsp; Look at the coin below.&nbsp;&nbsp; It&#039;s a Judd-235 half dollar that went for $4K this year.&nbsp; And yeah, graded PR64 by PCGS!</p><p><br /></p><p>While detracting, fingerprints aren&#039;t necessarily more so than some other bad things that happen to coins that get certified.&nbsp; Severe adjustment marks on early gold coins make them look like they were dragged down the street.&nbsp; Yes I know one &quot;defect&quot; is caused post-mint and one is pre-minting, but that&#039;s irrelevant to eye appeal.</p><p><br /></p><p>Cal</p><p><br /></p><p>[ATTACH=full]970846[/ATTACH][/QUOTE]</p><p><br /></p>

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