A good jug should, regardless of fashion, have a spout with a tear-off edge (i.e. no rounded edge) to make it more difficult to run around the edge. And – even more important - after the edge, the spout should first lead upwards (regardless of the position in which the jug is held). As a result, the liquid would be forced to flow upwards after going around the edge of the spout when pouring, but this is prevented by gravity. The flow can thus resist wetting even when pouring slowly and the liquid does not reach the downwardly inclined part of the spout and the body of the jug.
The image on the right shows three vessels with poor pouring behavior. Even in a horizontal position, that is standing on the table, the bottom edges of the spouts do not point upwards. Behind are four vessels with good flow characteristics resulting from well formed tips. Here, the liquid rises at the lower edge of the spout at an angle of less than 45°. In part, this only becomes apparent when one considers the normal maximum fill level: the glass carafe on the far right, for example, appears at first glance to be a poor pourer because of its slender neck. However, since such vessels are generally filled at most up to the edge of the round part of the flask, an advantageous rise at the neck is then obtained when pouring horizontally.Upward angle for the liquid when pouring. With the two lower jugs on the right, the high position of the spout (above the maximum filling level) means that the vessel has to be tilted quite a bit before pouring, so that the spout can also be pushed up directly after the edge (against gravity). indicates.
To avoid the teapot effect, the pot can be filled less, so that a larger tilting angle is necessary from the start. However, the effect or the ideal filling level again depends on the can geometry.
The teapot effect does not occur with bottles because the slender neck of the bottle always points upwards when pouring; the current would therefore have to "flow uphill" a long way. Bottle-like containers are therefore often used for liquid chemicals in the laboratory. Certain materials are also used there to prevent dripping, for example glass, which can be easily shaped or even ground to create the sharpest possible edges, or Teflon, for example, which reduces the adhesion effect described above.