From rLab Wiki
The overall setup for Lichtenberg figures with the oil heater as ballast and the variac to control the voltage
Burning a Lichtenberg figure, the red blocks are a pair of 5.5Kv 120mA transformers wired in series

We have made Lichtenberg figures at rLab from time to time. We don't keep the high voltage system in the lab for safety reasons but if you ask on the mailing list, Steve can bring it in.