The electric pickle doesn't really show anything useful, but it's fun. The pickle always glows on only one side, but not always the same one. The glow is clearly from sodium ionization like a sodium lamp. Presumeably the current heats up the pickle and boils water away and at some point ionizes the sodium. It will go for some time but once you unplug the pickle it won't glow again.
This gives a starting explanation, and I always like a link to Hyperphysics <http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/pickle.html>
Some plans here.