This is fun funnel experiment that proves that an empty bottle isn't, in fact, empty and to fill it with water we need to make sure that air can escape. If a funnel is properly sealed to a bottle and a lot of water is poured into it at once, water should just stay in there and not go through to bottle. In our case, play-dough didn't make the seal completely air-proof (vortex in a funnel did not help too), but we had a chance to compare the speed of filling two bottles anyway #TheDadLab | TheDadL