"Tinfoil arc lamp"

This is a weird phenomenon I discovered. The electrodes are made out of aluminum foil and when just right current passes through the arc, the tips of the electrodes burn away a bit and create blobs of oxide, which get heated to incandescence. After that the arc can be stable half an hour without the electrodes burning away.
I think the efficiency could be comparable to a low-wattage incandescent bulb.
The thing in the foreground is a high voltage transformer.