DC HV Generator
0.05uF Cap @20KV
Two Shallow Dishes
Adhesive Aluminium Tape
Connect the HV supply to the capacitor. Attach a piece of foil to each of the plates so the foil extends down to the bottom of the dish on the top and attached to a wire on the outside.. Arrange the plates so there is a 10mm gap between them and the foil furthest away from the gap. Fill the plates until the water is level with the edge of the plates. Tilting the plates slightly may help to get the water evenly along the gap edge.
Connect the two wires from each of the plates to each terminal of the capacitor.
Charge up the capacitor until the gap between the plates breaks down giving a display across the surface of the water on both plates.