Knifemaker,
Try doubling up another sheet of foil so you have 8 layers and just keep your hot plate set as low as it goes. Don't turn it up see what happens. If after 10 minutes you don't turn the plastic clear turn the heat up a little and wait.
Trust me it's you not the plastic I had the same problem as you when I first started. I kept burning and I swore I had a bad batch. I just heated it s-l-o-w-l-y and finaly found a setting point where I could heat and now I am good.
I learned the layers of foil tip from someone here. It works when I dip tubes I can leave my plastic on the burner for an hour and still not scortch or burn my plastic. I use a steel pan with a pour spout from wal mart. Good luck don't give up you'll get it. Once you get to pouring you'll probably have trouble with air bubbles but I will help you tackle that latter.