Copper electrodes for zappers are badly obsolete. Copper oxidizes rapidly in air and requires a caustic cleaner to remove. Sweat or moisture from the skin accelerates this formation.
That is why the Thundervolt zapper does not use copper handholds. We use zinc-plated steel tubes, which do not rust, corrode or oxidize. Zinc is a body-friendly metal and many men are zinc-deficient. We also have a Body Tester to measure the effectiveness of zapping. Visit us at https://zapper-zap.com/.