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<p>[QUOTE=&quot;-jeffB, post: 1589323, member: 27832&quot;]Short answer: just let it sit in the package until it reaches room temperature.</p><p><br /></p><p>Long answer, because I seem to be in lecture mode this morning:</p><p><br /></p><p>Moisture will condense onto a surface that&#039;s colder than the <i>dewpoint</i> (one measure of humidity) of the air around it. When that happens, water from the air will condense onto the surface; this warms the surface, and dries the air (reducing its dewpoint).</p><p><br /></p><p>When the surface is <i>warmer</i> than the dewpoint, the reverse happens -- moisture <i>evaporates</i>, cooling the surface and raising the air&#039;s dewpoint.</p><p><br /></p><p>Now, let&#039;s imagine that I&#039;m going to ship a coin to you. Today, the dewpoint here is 57 degrees -- it&#039;s quite humid for December -- but the temperature is 64 degrees, and that&#039;s what temperature my coin is. No condensation. I put the coin into a flip, put it in an envelope, and send it off.</p><p><br /></p><p>The package goes through the mail system, and goes into an unheated Cleveland mail truck Tuesday morning. The outside temperature is 28 degrees, and the packages in the truck get almost that cold. If the package I sent is completely air-tight, the air inside it is cooled below its original dewpoint, and moisture condenses onto the inner walls of the package (since they get cold first). But there&#039;s so very little air in the package that this condensation is unnoticeable, and it won&#039;t affect the coin.</p><p><br /></p><p>Now, you bring the package into your house, and impatiently unwrap it. The coin is at 28 degrees, and your house is at 68 degrees, with a dewpoint of (say) 48 degrees. When you remove the coin from its flip, moisture starts condensing onto it. Since there&#039;s a LOT of air in your house, moisture KEEPS condensing onto the coin until it reaches 48 degrees -- by that time, the coin is quite wet. The coin continues to warm up until it reaches 68 degrees. By then, water is evaporating off the coin, and this continues until it dries back off.</p><p><br /></p><p>How do you avoid a wet coin? Simple. <i>Put the package in a plastic grocery bag</i>, and leave it there until the whole thing reaches room temperature. Any condensation will happen on the <i>outside</i> of the bag -- again, <i>inside</i> the bag there isn&#039;t enough moist air to cause significant condensation. After a couple of hours, the bag should be dry, and its contents should be at room temperature; take out the package, unwrap the coin, and you&#039;re fine.[/QUOTE]</p><p><br /></p>

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