Re: what plastic
I wouldn't try the lead pot for plastic. If you are going into production then you should buy a professional pot. If you are doing home pours like a lot of us then get a microwave and some pyrex cups. You can get a working micro in a flea mkt or pawn shop for under 20 bones.
I have been using Calhoun's medium for a year now and am satisfied with it except on light colors then I have to add heat stabilizer on reheats. I am getting ready to order a 2 1/2 gallon jug from Bear. His price is $68.50 and lots of places it is $55 per gallon.