Electrostatically charging a capacitor

To get the charge from the PVC into a capacitor, you could ground one side of the cap, and attach a wire to the other side of the cap. The end of the wire should preferably end in a fine point or collection of fine points, and you sweep this over the charged surface of the PVC to collect what charge you can.

If you use a smaller capacitor you will tend to get more voltage, but even a small capactior (e.g., 100pF) is probably only going to get as far as a couple of volts, even off a PVC surface charged to 10's of kV, because the capacitance of the PVC surface probably isn't even 0.1pF.

Sounds like you want a Leyden Jar (an early type of capacitor), here's a tutorial:

http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p049.shtml

This is a good way to explain the behavior of capacitors, actually. People talk about "charging up" a capacitor, but they don't actually store charge. They store energy in the form of a displacement of charge. The electric charge of an empty capacitor and a full capacitor are both 0.

If you charge up a piece of PVC and touch it to a floating capacitor, it won't accept any more charge than any other piece of metal of the same size. The reason capacitors can store so "much" is because you're removing charge from one plate and depositing it on the other. If you connect one terminal to ground, you should be able to add more charge to the other terminal, since an equal amount can "escape" to the earth from the other side.

http://amasci.com/emotor/cap1.html