The guys were doing some testing on copper wire and decided that the best way to see their test in action was to create a Jacob's Ladder. Who doesn't love these things? Paul quipped that every lab should have one of these on at all times, just as a matter of principle. At 12,000 volts, the arc was doing its thing happily.
After the tests were completed, you could visibly see the copper dust residue on the inside of the jar. The arc took the copper wire and, in the most scientific terms possible, made it go "poof" in a show of plasma and heat. Sounds fun, right?!
