“The first thing to realize is that when you pickle something you put it into a mixture of salt and vinegar. Salt contains ions, sodium ions, chloride ions, and salt solution is electrically conducting, but it’s not very electrically conducting compared to metal. So what you’ve got are two electrical conductors with a resistance in between. And when you pass a current through it, the resistor will heat up.”
…and it will glow and spark. Periodic Table of Videos uses slow motion and thermal imaging as they try a few different variations on this classic science demonstration from 2016: Electrified Pickle. Reminder: Sir Martyn Poliakoff at The University of Nottingham narrates.