I would like to know what would the best material to use to plug the bottom of seat tube, ( not the bottom bracket, but I show the bottom bracket anyway, its fairly small,) such that the caustic soda/ sodium hydroxide I pour into the top of the seat tube... such that it won't leak out. Rubber? cloth? something else? someone suggested old innertubes...
( I have cut off an aluminum seat post. but it is frozen and stuck in a steel frame. I have seen videos that say I can pour the caustic soda down the top of the seat tube and eventually it will dissolve the aluminum)
bottom bracket, seatube hole not visible obviously