Apologies for moving the camera around, the energetic behavior of the discharge rapidly rotating and ejecting sizeable bits of clay was an unexpected result, and I was a bit scared of the discharge hitting my camera halfway through the video (camera was only a few inches away from the discharge).
This experiment shows a high voltage pulsed DC electric arc discharging into wet clay and vaporizing the conductive moisture in the clay along its path to the cathode. As the moisture is carried away, leaving dry clay in the discharge region, the clay begins to break up.
Notice that small and large fragments of clay on the aluminum base are being attracted to the central clay chunk, this is likely due to electrostatic attraction between the fragments which have been imparted a net charge, and the discharge filaments underneath the clay (not shown).
Near the end of the video, the discharge becomes focused in a single area, building tremendous heat as indicated by the steam and light. We then see clay being pushed up from below. Had I used a softer clay, or clay infused with carbon or graphite, the clay would likely rise up -- like Rod Browitt's lightning blister -- without fracturing.
The transformer was made using a light dimmer (which utilizes triacs), the ignition coil from a car (around 8mH), and an AC motor-run capacitor with a capacitance of 20uF.
Video was taken on September 2, 2013
