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<p>[QUOTE=&quot;coinhead63, post: 1046972, member: 28001&quot;]The holder cases are made of clear acrylic (Dupont Lucite) or polystyrene depending upon the brand.&nbsp; Any kind of insert may be made of any of the following:&nbsp; polyethelene, polystyrene, Mylar<font size="4"> (polyethylene terephthalate), </font>or any other clear innert plastic that does not gas-off.&nbsp; Holders or &quot;slabs&quot; from PCGS, NGC, et al are sonicly welded together thus are more apt to be air tight.</p><p>&nbsp;</p><p>You are correct that the scientific term plastic refers to a state of a material especially when referring to deformation.&nbsp; In this forum you should keep in mind that the term &quot;plastic&quot; is a description of a class of polymers that are somewhat rigid but also flexible.</p><p>&nbsp;</p><p>With respect to cloth or any other natural fiber, they have an affinity towards absorption of fluids and will have an osmotic tendency (attempting to attain the same relative humidity as their environment).</p><p>&nbsp;</p><p>By the way, when you wiped your wet kitchen counter with plastic did your hand get wet?</p><p>&nbsp;</p><p>You obviously have a rather extensive knowlege of polymers (plastic) and you don&#039;t accept information unless it has been proven by the scientific method and that&#039;s fine.&nbsp; I, myself, don&#039;t automatically accept everything I am told either.&nbsp; It must be backed by a historical record.&nbsp; I&#039;m sure there may be a chemical engineer in this forum that could explain even further than I have about the composition, benefits and drawbacks to each type of coin holder on the market.[/QUOTE]</p><p><br /></p>

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