Build the capacitor itself?

I have a question about the capacitor itself construction. I was wondering how much cm square aluminum foil is for 1 pf capacity needed, if you take plastic film as an insulator thickness of plastic film and whose material depends on the.
 
 Without HV electrical  detailed information you won't go further there... so I'm thinking it with thick plastic bags to make make it when two were film. (these formulas of wiki I not smart... will XD because I'm dähmlich)Just how much stress would keep it from then? Just a small build, voltage increase until he strikes through, then you know how much they endure: head bang:
Or you look even as voltage fixed your film is exactly and expect out then it friends.