If you aren't already aware, there are some folks who use a couple million volt particle accelerator to make lichtemberg figures in acrylic. If you watch some of their videos over at http://www.capturedlightning.com/frames/lichtenbergs.html#Make it looks like they only leave the acrylic under...
I am new to this site and looking forward to filling my days with much more physics. It's about time that I join these forums, and I look forward to meeting new people and enjoying conversation.