any suggestions how to make that hole in the cork? would a regular needle be ok?
given I am using rod, how often would i have to change these rods?
Be careful not to place more than around 3 grams of citric acid into the tube, as the more citric acid you have, the higher the pressure that builds up.
With 3 grams of citric, you reach about 6 or 7 atmospheres of pressure. If you start going to higher pressures, you find your plastic bottle starts to stretch and bloat out in a disconcerting way! Then if you reach 12 atm or so, it will actually burst (although when a plastic bottle bursts, it's not particularly dangerous).