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<p>[QUOTE=&quot;eddiespin, post: 501752, member: 4920&quot;]OK, let me begin by clarifying a few things. I said I have &quot;examples, comparison-pictures.&quot; I don&#039;t have any before and after pictures of the same coins. These comparison-pictures compare the water-cleaned coins to the mineral oil-cleaned coins. Say about 12-15 years elapsed-time since these coins were all cleaned.</p><p><br /></p><p>A little more on my &quot;unscientific method.&quot; I was cleaning coins, not conducting some double-blind study on the long-term effects of mineral oil on coin surfaces. It just turns out, I&#039;m able to compare these two groups of coins, after all these years, and draw some conclusions. You should also note, I got all these coins, all at once, in a bag of about 1000 &quot;uncirculated&quot; cents. That is to say, that&#039;s how the seller at the flea market had represented the bag. The majority turned out to be anywhere from VF-EF, and there were indeed a few that were uncirculated. Every one of them, though, had cartwheel luster, to varying degrees.</p><p><br /></p><p>Continuing on, got these home, dumped them out, and separated-out the ones I thought needed cleaning. Some of those were pretty encrusted. Basically, I gave that whole bunch a water bath for about a day or so, then removed each coin, individually, and brushed them off under warm, running tap water, with a paint brush, something like that. I then let them dry, and put the ones away that pretty much cleaned-up, while dumping the rest, the stubborn cases, into a plastic bucket of mineral oil. Put the lid on that. Maybe changed the oil one or two times as the foreign material loosened and I could see it in the suspension. Give that anywhere, I&#039;d estimate, from about 4-6 months. Then, took them out, put them in water for a couple of days to dilute some of the oil, then rinsed and brushed each coin, individually, again, under warm, running tap water, let them dry, then put them into another bag. Even every one of these &quot;oiled coins&quot; had their cartwheel luster, even after all that. Fast-forward about a decade, and now the surfaces are all &quot;flat.&quot; The coins are still &quot;shiny,&quot; but there&#039;s no more cartwheel luster. It&#039;s a different kind of shine. OTOH, the ones I had just cleaned in water, still have their cartwheel luster. </p><p><br /></p><p>That gets us, finally, to the pictures. The first is two piles; left pile is just water, right pile is the oil. The next two, same idea; left coins are the water coins, right coins are the oil coins. I just happened to find some same-dated coin to side-by-side-compare out of the two groups of coins. That cartwheel luster on the left was what the ones on the right used to have, even when they came out of the mineral oil.</p><p><br /></p><p>One more thing. You shouldn&#039;t conclude from this that mineral oil is harmful to coin surfaces. The harm, if any, appears to show only after time, after a prolonged &quot;bath.&quot; In other words, you&#039;ve heard of an acid bath? This would be at the opposite end of that pH scale, a base bath. Your guess is as good as mine why some of those surfaces are apt to go &quot;flat&quot; over time. One theory might have to do with the difference between acid and base. An acid bath will kill any micro-organisms that may be present on a coin&#039;s surface, while a base bath will only support their growth. Guess we&#039;ll leave that one to the bio-chemists...[/QUOTE]</p><p><br /></p>

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