Here’s a great new Instructable in the Make group on building a five foot tall Jacob’s ladder from Ewilhelm, he writes “This classic climbing arc completes any mad scientist’s dungeon. Don’t touch the electrodes: they’re at 12 kV! Get a neon sign transformer rated for 9 – 12 kV and 30 mA. Make sure it’s an old style, heavy coil transformer and not solid-state. The solid-state transformers won’t start the arc. I got a Transco 12 kV 30 mA transformer on Ebay for $35. It didn’t have a wall plug, so I wired one on.”… Link.