> I have found that among the many YiXing GungFu teapot "styles," those well
> made with a straight upward pointing spout work best in the drip
> department.
> The last drop is "pulled back" into the pot, as it ought to. This has to
> do
> with design much more than clay roughness and surface tension. Take it
> from
> Michael, the used-to-be potter.
>
> Michael


Its design plus material plus size and shape (that defines the dynamics and
geometry of how fast it is rotated around its horizontal axis during
pouring. Straight upward design works good for smaller pots and yixing clay
has very high surface tension (watch drips of water sitting on its surface
at different slope angles and compare that with the behavior of water drops
on glazed porcelain) Same design does not work for large kettles at all also
because that design implies lifting the pot quite high and rotating it at he
higher angle, which is difficult with heavy pot. That is why traditional
kettle has a bent spout that allows for smaller rotation angle and almost no
lift.
Yixing pots are meant to be emptied into chahai by placing them almost
upside down with their spout inside chaihai opening. That is not at all the
dynamics of the usage of large teapot or kettle. Thus the differences.

With al due respect to a potter from a scientist.

Sasha.