Look for some mylar online... Foil Duct tape isn't anywhere near reflective enough. It's better than nothing but I'm pretty sure its around the same as aluminum foil at reflecting 33% of light. Mylar is 99%. It's pretty cheap stuff too. Perfect for the rubbermaid. Emergency Blanket would be to the same effect.

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"We had two bags of grass, seventy-five pellets of mescaline, five sheets of high-powered blotter acid, a salt shaker half full of cocaine and a whole galaxy of multicolored uppers, downers, screamers, laughers....Also a quart of tequila, a quart of run, a case of Budweiser, a pint of raw ether, and two dozen amyls....But the only thing that worried me was the ether. There is nothing in the world more helpess and irresponsible than a man in the depths of an ether binge...."