Rigid acrylic holders are heavy, bulky and a nuisance to take apart but they do protect notes well from inadvertent handling damage and dropping. However, whatever you do, don't spill red wine or coffee on the holder because the liquid will imbibe instantaneously through the gap between the plates via the well-known scientific principle of "capillarity" and the liquid will be all over the note inside the holder before you know what has happened (and it will take you several fumbling minutes to open up the holder)! It's the same, of course, with regular mylar holders, and I'm not joking. Believe me my friends because I've done it. I ruined half a dozen scarcer AU/UNC asterisk notes with red wine about two years ago and I had to sacrifice them on eBay at a small fraction of what they were originally worth. I extracted the notes pronto and raced to the wash basin but I was too late, the staining damage had already been done. By the way, these were the only notes that I've washed and pressed in the last twenty years!
A good thing about rigid acrylic holders is that they allow the notes to breath whereas TPG plastic holders do not. By way of example, I purchased a large collection of foreign coins recently that had literally not seen the light of day for 25-40 years. The large majority of the 2" x 2" plastic coin holders were sticky and gooey inside although I was able to clean up the coins fairly easily using grease-removing solvents such as acetone. Even annual sets of coins in soft plastic holders from the highly respected Royal Australian Mint and the Japanese Mint had suffered the same "gooey" fate (see image below showing the notorious "green slime" on a 1979 set)! However, once a bank note has been similarly affected by the gooey slime it's usually "curtains" (I've seen these greasy "translucent" notes offered on eBay from time to time).
I'm sure that TPG (e.g., PMG) sealed plastic holders will be safe for 5-10 years, but what about 20 or 30 years with no air circulation whatsoever and with all of the inevitable bacteria and mold spores breeding inside ..... ?! Would you want to take a chance on a US $1000 "Grand Watermelon" note worth $2,000,000 ..... ??
Come to think of it, do the TPG companies seal their notes in a vacuum environment??
{http://images.andale.com/f2/115/106/3433819/2007/3/25/1.jpg}
« Last Edit: March 25, 2007, 01:06:38 pm by Ottawa »
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" Buy the very best notes that you can afford and keep them for at least 10 years. " (Richard D. Lockwood, private communication, 1978).