I built this generator many years ago. The globe is a 23cm.white glass lamp shade, covered with rubber cement and segments of aluminium kitchen foil. Unused for many years, the synthetic rubber band had perished. After some experiments I found a substitute rubber band that, in combination with the existing black polystyrol rotor, can generate a fat inch-long spark and charge up a paper tassle (see photo). It is driven by a modest induction motor (with original price tag: 1,50 DM.) The minus terminal of the generator is connected to earth.
Van de Graaff generator
My hope is to use the generator to calibrate an electrostatic meter that I will use to measure the atmospheric static on a vertical radio antenna suspended from a kite - (yes, I shall observe all safety precautions including an adequate bleed resistance to ground.)