Just curious, when there is only a bit of toothpaste left, I have to squeeze little by little from bottom up. But then after using it, I'll have to do the same thing next time around. Obviously the toothpaste has to settle down the tube. Why and how does it do that?
The plastic material has internal stresses that retain the shape it was cast in originally. Since it is attached to a round head it tends to form a sort of flattened cone. The toothpaste moves back up the tube to fill the available space as it is a type of really thick fluid. The shape may also lead to the toothpaste moving upwards due to capillary action (similar to how water moves up a very thin straw) To combat this effect, you can buy a little squeezy thing that rolls over the tube to prevent the toothpaste from moving backwards, or you can fold/bend it over as you use it like many people do. I store mine upright on the cap so the toothpaste settles at the end I squeeze it out of. The tube also uses less counter space when you store it upright as compared to laid over on its side.
