[pct-l] Shiny Wine Box Bladders

[brick@fastpack.com (Brick Robbins)]

At 06:33 AM 10/26/01, you wrote:
>The one shiny
>bag was left virtually unprotected under a ledge, but it wasn't even
>touched! Our theory is that a squirrel saw the mirror image of himself
>in the shiny bag and ran away.

The shiny "stuff" is a  plastic/metal sandwich called Mylar 
(....technically: Mylar is a plastic called polyethylene terephthalate and 
comes with or without the metal, but most of us only notice the metalized 
stuff).

Regular plastic "breathes" (ie is gas permeable) so the squirrels could 
smell the water inside.
Mylar does NOT breathe, so the squirrels couldn't smell the water, and left 
it alone.

See http://www.darylscience.com/VanillaBalloon.html for an experiment that 
demonstrates this in a way even human noses can detect.

This lack of breathing is why Mylar helium balloons stay inflated, while 
rubber helium balloons go flat quickly. The helium cannot get through the 
Mylar.  Helium (He) is one of the smallest molecules, so if it cannot get 
through Mylar, larger stuff like Oxygen and Water don't have a chance.

This is the same reason that freeze dried food comes in Mylar pouches. With 
the oxygen absorber packed inside (the thing with "do not eat" printed on 
it) oxygen can't get in to ruin the food, and it stays good forever.....

See
http://www.dupontteijinfilms.com/datasheets/mylar/productinfo/properties/h37250-1.pdf
for more information on Mylar.


--
Brick Robbins                       mailto:brick@fastpack.com