What Are Lichtenberg figures?

Lichtenberg figures are branching, tree or fern-like patterns that form as the result of high voltage discharges on the surface of, or within, electrical insulating materials (dielectrics). The first Lichtenberg figures were actually 2-dimensional patterns formed in dust on the surface of charged insulating plates in the laboratory of their discoverer, German physicist Georg Christoph Lichtenberg (1742-1799. Professor Lichtenberg made this observation in the late 1700's, demonstrating the phenomenon to his physics students and peers. The basic principles involved in the formation of these electrostatic figures later evolved to become modern xerography and the science of plasma physics. Lichtenberg used electrostatic devices to charge the surfaces of various insulating materials such as resin, glass, or ebonite. He then sprinkled a mixture of finely powdered sulfur and red lead (lead tetroxide) onto the surface. The powdered sulfur was attracted to the positively charged regions and the red lead to negative regions, thus making the previously hidden regions of charge clearly visible.

Lichtenberg also observed that the shapes of the positively and negatively charged figures were significantly different. Positive figures tended to be star-like with long branches, while negative figures tend to be round or fan-like. By carefully placing a piece of paper onto the dusted surface, he was able to transfer these image to the paper, demonstrating what was later to become the process of Xerography. Drawings of positive and negative figures actually captured by Lichtenberg are shown below.