Heated plastic gives off molecules that are detrimental to your body.

Letting a trash bag sit on a roof is asking for a healthy dose of things you do not want to be consuming. I strongly advise against using plastic for anything involving heat. I can't imagine you don't notice a funk taste to it from the sun-baked plastic 'container', either. Granted, everclear doesn't tast great to begin with. But... I just can't imagine the tincture doesn't have essence of trash bag in it when you drink it. I'd be very wary of that method to the point of taking it from you and throwing it in the garbage, no offense. I just don't want you or anyone else having health problems down the road because of dioxyn consumption from heated plastic.