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<p>[QUOTE=&quot;Hommer, post: 2106736, member: 73266&quot;]I want to attempt an explanation of how &quot;Original Mint Luster&quot; and &quot;Mirrors&quot; are formed, on the surface of a coin, during the minting process.&nbsp; Using a scientific explanation in layman&#039;s terms, my hope is that whomever reads this can achieve a good understanding of the processes that create both without too much difficulty. At times you may wonder, &quot;where is he going with this&quot;, but I promise, if you hang with me, I&#039;ll tie it all together. </p><p><br /></p><p>First let&#039;s explain luster, or what causes the reflection that we call luster. Luster is nothing more than the reflection of light. </p><p><br /></p><p>Most all solid substances reflect light.That is how we see color, remember the color wheel in grade school, white light is made up of all those colors. When light is shown on gold, all colors of the spectrum are absorbed, except those that are reflected back, that give the gold color. Absorption of color is a little too complicated for this discussion, and probably doesn&#039;t seem relevant, but Iet me explain.</p><p><br /></p><p>Lead is typically considered dull grey with no reflection. Grey is a color, but at times it too can have luster. If you have ever experimented with pouring your own fishing weights you will have observed it. </p><p><br /></p><p>When melted down, the liquid lead has luster as does freshly poured lead that has hardened. Why is that and what on earth does it have anything to do with coins? The coin part will come as I promised, but for now let&#039;s discuss luster.</p><p><br /></p><p>How liquid lead reflects light so well has to do with what we call surface tension. </p><p><br /></p><p>We have all heard of surface tension, but what actually is it? To explain it could get complicated but it really is easy to understand. Tiny molecules of the same substance are attracted to each other and pull themselves together like a magnet. The outer most layer of molecules do not have anything pulling at them on one side, so their attraction to the inner molecules is much stronger. Kinda like being pulled by your arms and legs, in opposite directions, until someone lets go. This added attraction, or pull in one direction, makes them very compacted. So compacted in fact, that very little light can be absorbed. This in turn, gives us a reflection or luster. Raindrops have surface tension.&nbsp; Ever watched as two beaded raindrops attract one another and become one? . That same surface tension and luster remain when the lead cools and hardens but the luster is confined to the surface and remains very thin.</p><p><br /></p><p>Another thing I believe should be explained here is how a cool ( there is heat from friction in the process) solid metal can flow like a liquid. When a planchet is stuck in the coining press, the metal of the blank planchet flows to the recesses in the die to form the coin. How is that?</p><p><br /></p><p>To explain how cold metals can flow, I want to use water and mercury. We all know that water becomes a solid or ice at 32ºF and normal atmospheric pressure. But when ice is placed under higher pressures it will return to a liquid at that same 32º. Crazy huh? Case in point; when you scrape the ice or frost off of your windshield, ever noticed ice forming right behind your scaper? Have to scrape it again? This is because the pressure you put on the ice with the scraper caused it to return to a liquid state that refrose when it retured to normal pressure. Cool huh?</p><p><br /></p><p>Even cooler is that mercury is a liquid at normal atmospheric pressure, but will become a soild in a vacuum or a vapor at high pressure. Surface tension is what makes liquid mercury look like a mirrored ball.</p><p><br /></p><p>Now to tie all this rambling together. When a coin is struck in a press, it is put under tremendous pressure. So much so, that the metal surface of the planchet becomes liquid and begins to flow to fill the die. </p><p><br /></p><p>Since the metal is now liquid it takes on the properties of surface tension and becomes lustrous. When the pressure is released, or obsorbed by the anvil, the metal will again freeze in its current form and all those lustrous flowlines remain.&nbsp; </p><p><br /></p><p>Being that these are actually tiny thin mirrors in a way, they will reflect light in crossing patterns that tend to give the reflection a texture. Like a hologram effect. </p><p><br /></p><p>Oh and the cartwheels. Most of the flow of the metal will be from the outside of the planchet to the devices or designs engraved in the center of the die. As the metal flow gets closer to the center, the flow lines become concentrated because they have less room to flow. This is what makes the flow lines appear to be spokes that radiate and get wider from the center.&nbsp; When the coin is rotated in light, the luster of those lines appear to go around, just like the spokes in a cartwheel.</p><p><br /></p><p>Mirrors? </p><p>To understand this one is fairly easy. It implements all the above explanation of luster less the flow lines. When a proof coin is first struck, it too will have lustrous flowlines, but proofs are struck at least twice. Since most of the flow of metal has filled the devices in the die on the first strike the second strike causes these lines to melt and flow together. The result is a flat surface that resembles a mirror. Kinda like the surface tension of a clear lake on a still morning.</p><p><br /></p><p>I sincerely hope this, as rough as it is, actually makes sense.[/QUOTE]</p><p><br /></p>

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