I've been experimenting with different techniques for these Lichtenberg Figures using larger pieces of MDF. Feel free to leave suggestions in the comments if anyone has any good ideas.
In the figure above I coated the whole piece with electrolyte (excluding the edges), and then tried moving the electrodes around to different nails. It turned out better than the previous ones using two fixed points for the electrodes, but the current kept wanting to jump back to previous carbon paths, so the second and third burns had less detail than the first.
The figure above is larger than the previous two. In this one I did two parallel coats of electrolyte and burned the vertical patterns on the left and the right. I then painted a wide, slightly diagonal coat of electrolyte across the middle, connecting the carbon paths on the left and the right and did the burn using the bottom left and top right nails. The only thing I don't like about these is the light stain that the electrolyte leaves, which shows a contrast between the parts that were coated and the parts that weren't.
I have to give credit for this idea to my wife. We had been looking for a "multiple-panel" piece of art to hang in our bedroom, and she suggested trying to do a paneled piece with the Lichtenberg Figures. Each panel is 16" x 24" and was cut out of one piece of 2' x 4' MDF. The panels were burned separately using many different points for the electrodes. I tapered the electrolyte solution down to points at the edges of the panels to make sure that the burns lined up from one panel to the next. Unfortunately I decided to use 1/2" thick MDF for this so that the panels would hang better and would be less likely to warp. This thicker MDF was much more absorbent than the 1/4" MDF that I used for the previous burns, so the electrolyte soaked in quickly and created a thicker burn pattern with less detail. I like the design, but I think I'll try it again with the thinner board.
Edit: Instead of making a whole new post I'm just adding the above picture to the end of this post. This is the three panel piece I did on the thinner, 1/4" MDF. As I expected I ended up with a lot more detail. I think in order for this to be worthy of hanging on a wall I'm going to have to add some color to it, so the next experiment will be to see how watercolor paint takes to MDF.