here is the link : http://www.youtube.com/watch?v=iG0_LAefrnI&feature=related

i,ve tried this experiment several times before,i used 0.7 MM lead for those mechanical pencils,i got the best results driving it with a 24 Volt 2 Amp power supply,i made supports for the rod so it wouldnt break when it got very hot.

i think you have to use wooden pencil lead instead of mechainial pencil lead. but, i guess that works too! 

besides being easier to obtain,the mechanical pencil lead is thinner and has less resistance which means it heats more and glows white instead of orange.

I made arc lamps using the graphite rod from a old "D" cell, driven from 28V. Aside from the brilliant white light, it blanked out radio reception for meters around my workbench, whilst I used it to weld aluminium plate.

yep,i didnt think arcs could form at such low voltage i used it to melt coins.

I've also tried an arc light too, using lead from a mechanical pencil and a 9 volt battery.

if you really want to make a carbon arc lamp,you could use carbon rods from a battery,i know of some transformers that can supply 12 volts at 35 amps,50 amps short circuit!!! 

Hey Sean you opened a cell? Isn't there any stuff that can burn the skin?

Yes, the contents can burn. I gently squeezed the cell in a vice a few times to loosen the grip around the rod, then withdrew it using pliers to grip the metal tip. It comes out mostly clean, just needing a little washing in cold water with washing soap. I used ordinary cheap cells, not the alkaline type, as these are a totally different construction.

Sean: OK I don't have anything else than alkaline cells. Instead I use the lead in a wooden pencil. I attached two leads to a wire and hooked up the wires to a transformer that supply 40V and 2,5A. You make a contact between them during 1/4 of a second and voila! An arc starts, and that's BRIGHT!! Unfortunately many problems occurs:

- The negative rod burns pretty fast
- The arc isn't steady for more than 7 sec. and shuts off after 12 sec.
- There is an important color shift at the end, sometimes one of the wire melt.
- A lot of smoke is produced