For winter 2016 I made Lichenberg Figures. I used a 5kV 10mA (50W) neon light transformer. I also experimented with a 2kW microwave oven transformer, but found that the lower powered neon transformer produced finer, better, and safer results.
To produce the figures, I would first apply the electricity to the wood, often at the corners. Initially the resistance of the wood is not sufficient to allow any burning. Then I would use a spray bottle full of water/baking soda to moisten the surface of the wood until the electricity could find the path of least resistance and start the burning reaction.