Homemade light bulb #12

This incandescent light bulb is made from a pickle jar, refrigeration vacuum pump, and a piece of mechanical pencil lead. As it burns, pieces of graphite flake off, making the filament thinner and hotter, until it burns out. At the end I do not increase the voltage, that is just what happens as the pencil lead decays away. If I remember correctly it runs at about 6 volts at a few amps.