hazardjollyroger The equipment on this page can kill you.

If a high voltage is applied to a pair of electrodes in a ‘V’ shape and the gap at the base is small enough to cause an arc to form, the arc will climb the electrodes.

The arc is forced upwards by the thermal and magnetic currents and is stretched until it breaks. It then re-strikes at the base and the process continues. All you need is a small transformer like a neon transformer or boiler ignitor that can deliver around 8KV or more and you can build one.

A horn gap made from 2 wire coat hangers.

horn gap

This transformer produces 35KV peak and the arc can be stretched to about 6 inches before it breaks.

horn gap psu