I used cd rom and string when I was etching hole in stainless steel, after few minutes bubbles accumulated and significantly slowed down the process, pulling it

I used cd rom and string when I was etching hole in stainless steel, after few minutes bubbles accumulated and significantly slowed down the process, pulling it out of solution every minute would burst the bubbles and etching could continue. Another time I used led from keyboard (NumLock/capslock/scrollock) to trigger reed switch relay that would ground piece of aluminum foil taped to the phone screen (I was grinding in some MMORPG game).