fill a bottle 3/4 the way with water and add 2 tbsp of dish soap and 1 marble close the lid and move in a curcular motion
Select as Best AnswerUndo Best Answer
I nearly sent you off to Google, but I see there is a twist to your question - you want a tornado in a SINGLE bottle - not the usual one on top of the other arrangement.
The best way I can think of is to put a small bar magnet in the bottle and have a motor spinning underneath also with a bar magnet. This would give you a pretty good vortex, and is the way some laboratory stirrers work.