On 30 Oct 2001, at 14:51, Sandy Sandfort wrote:
Mike [mmotyka@lsil.com] wrote:
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.
Or... is there something that REACTS to freon in an interesting way...?
S a n d y
I think freon is incredibly inert, that's why it's used. My impression is that virtually any transparent liquid will do a reasonable job of making the envelope transparent, but the considerations are that you'd want something that doesn't leave a residue and won'tr make the ink run. I believe that paper is white for the reason that snow is (as opposed to the reason that titanium oxide is), that is, you've got a bunch of surfaces where the index of refraction changes significantly from that of air and there's a chance of reflection at each surface, but the actual paper fibers are transparent. The liquid you spray on is filling in the gaps with something with an index of refraction much closer to that of the paper fibers. Pretty sure that's more or less how they work. Definately there's no chemical reaction going on. George