Most helpful positive review
4 of 4 people found the following review helpful
A fascinating toy
on 30 October 2014
This device has fascinated literally hundreds of students in the schools I teach at. As such, it is a great little device for discussing pressure, ideal gasses, energy conservation, fluids and circular motion.
For bottle selection, you'll need 2 litre bottles.with the larger necks. I found these were more common in own-brand soda bottles or mineral water rather than branded soft drinks. Once you find them, put in some distilled (boiled and cooled) water and a bit of glitter and you have a long lasting desk-toy.
Someone noted that the bottles get "sucked in". This happens as the air inside the bottles warms and cools. The best thing to do is to shake the water to allow the temperature and pressure to change, then twist the bottles and let more air into the bottle.
The only real issue is that when spinning the water initially, if the user is a little over-zealous, the plastic does start to show stress fractures. Still five stars.... after all, it hasn't broken yet, despite the best efforts of the students.