After years of blandly accepting something in my everyday life, I suddenly this morning started wondering, "How on earth does this work?" I refer, of course, to the lowly Glad sandwich zip-loc sandwich bag. One side is blue, the other yellow. When zipped properly, the closure turns GREEN.
Of course, yellow+blue=green. I get that part. But the amazing part is that when the bag is ALMOST zipped, it isn't green. When you jam the two sides against one another, but mismatch them so they don't lock, no effect. Only when it is locked does it look green. It's a purely visual illusion, and I can't figure out how they make it work ONLY when the lock is tight.
The reason I thought you-all might find this interesting is that you deal with gels all the time, their interaction, and above all, ILLUSION. This is a very, very successful one.
I think this color thing works because the translucent plastic zippers work similarly to fiber optic cable, just in a much cruder sense. For the color-filtered light to blend and "turn green", the plastic surfaces have to be in full contact to transmit some of their colored light to each other, and you only get that if the seal is good. Just a guess.
"The thermos: it keeps hot drinks hot and cold drinks cold - how do it know!?!?!"-Robin Williams