Polycro Bathtub!

It's used for window insulation because it stops air infiltration around poorly sealed windows and window frames. It has essentially no resistance to heat transfer, other than by preventing air movement. So, no, it won't keep you much warmer if you use it as a ground sheet or bathtub, except if it keeps you dry.

So, I may not have this right yet, but I really liked my most recent trip with a bigger than my tarp size piece of polycryo. I used my trail shoes in two of the corners and then took the poly and folded over the shoe so that the corner was raised. I used tallish rocks on the other 2 corners and did the same, so the poly is now raised in all 4 corners (folded up and inward over the object) Then for the sides I just folded over around a few sticks and viola, 2 to 5 inch berm all the way around. Sadly it did not rain to test it ;)

Kathleen: Nice! I'll remember this. Especially as I just experienced a small creek of rain water and hail flowing under my tent during a seven hour thunderstorm.

Polycryo: it's made out of mournful parrots, obviously. Poly-cry-O! there's just an utter lack of scientific sensibility on this forum.

And here I came expecting a method for backcountry bathing and getting clean… Actualy I recall reading of someone taking a 55 gal black garbage bag for that purpose. You put some warm water in the bag and climbed in and cleaned up! I never tried it, but at lest you'd be out of the breeze.

"For a nation that regularly butchers the English language, eg aluminum for aluminium,…"

Hey now, the English chemist responsible for naming it used "-um" before settling on "-ium."

At any rate, I'm happy with either ore.