Well, I was watching CNN and it looks like the Postal workers now are armed with a new weapon.. Against terror of course. THe whole cant read someone elses mail thing is out the window it looks like, they can spray this go on the letter and read through the envelope.. It seems implausable but its CNN, they dont lie right? well ANYWAYS, I now have a nice stash of black construction paper...
Yes, that would work nicely as the outside sheet.
"You spray it on and it temporarily makes the envelope clear," said Robert Schlegel, vice-president of the makers, Mistral Security, of Maryland. "It leaves an odor for 10 to 15 minutes, but there is no smudging of ink, no stain, no evidence at all. The envelope is transparent for a few minutes and you can respray it hundreds of times without leaving any stain."
I would bet that there is SOMETHING that is dissolved by liquid freon. Just mark your letters with the stuff and look for the integrity of the mark at the other end. The USPS won't be checking mail this way anytime soon. If they were they would use some sort of freon recovery system to contain costs. Oh, well, it will soon be time to go buy $2.95 stamps to pay for UV, E-beam, freon and zoot suits. Mike