Teapot Pour

[Hulk]

This is the twelfth teapot*.
It pours well - solid dependable arc of fluid, which stops predictably and, and, no dribble along the bottom edge of the spout!
I'm also happy with: the overall feel; the shape/profile; boss lid that's heavy without being over heavy, stays in place through full pour-out, and fits well; the color.

I'd looked at many many teapots and searched for The Authority on dripless pouring in general, teapot spouts in particular.
Although there is a study on spiraling path of liquid flowing down a glass rod, uhm, didn't find that helpful - maybe there's something there.
There are many articles, forum posts, etc. that offer helpful suggestions, however, I didn't find anything truly definitive.

Features that may help:
  spout tip higher than (reasonable) fill line;
  lots of holes between the spout and pot body, so the liquid doesn't back up in the pot when pouring, and doesn't back up in the spout once pouring ends;
  the "sharp edge" at the pouring lip that so many mention;
  design such that the liquid prefers running back inside the spout over dribbling down the outside when pouring ends.

Ah, that last bit!
Good luck.
I hope to replicate my good fortune in future...
I'll post some detail pics later on.

From last Saturday's glaze fire.
Aardvark Buff clay, cone 5; exterior Rutile Green glaze, dipped; interior my low COE liner glaze, poured in, poured out;  chattermarks filled with Clear Blue glaze.
The tea cups are very close to same size; the camera I'm using distorts the image, especially away from center.

This is my last attempt before branching sideways into a spout test, making an array of test spouts that fit up to a test vessel, perhaps a soft rubber ball with spout and vent holes, press up against the spout to test, huh. I still might do that. No doubt others have done something similar already. ...the protocol for such is simmering

*The prototypes that poured reasonably in bisque were glazed and fired; none poured without dribbling, once glazed.
Several prototypes are still in bisque; as shelf space is tight, they'll likely see the bin, soon.

[Bill Kielb]

6 hours ago, Hulk said:

Features that may help:
  spout tip higher than (reasonable) fill line;
  lots of holes between the spout and pot body, so the liquid doesn't back up in the pot when pouring, and doesn't back up in the spout once pouring ends;
  the "sharp edge" at the pouring lip that so many mention;
  design such that the liquid prefers running back inside the spout over dribbling down the outside when pouring ends.

Here is a little engineering fun that could spark some additional thought. The more laminar, the better. One can do tricks with laminar flow.

A fun practical  example, 14:02 is probably most relevant.

https://youtu.be/y7Hyc3MRKno

 

Edited October 7, 2022 by Bill Kielb

[Callie Beller Diesel]

Something that I did years ago to figure out pouring mechanics was to make a bunch of creamers with spouts, rather than entire teapots. You can do a lot more of them in a shorter time span, fit more of them in the kiln to test, and use less materials to make them.  Once you’ve got the idea on a smaller scale, you can then work on making them larger. 10/10 recommend. 

[Mark C.]

I have found a few tricks and there are many more with spouts. One is to have plenty of holes in main body so fluid can flow well. The other is a sharper edge at pour lip. I cut mine with a metal edge and try to keep it sharp (not sponging to be round) the other is the spout at cone 10 unwinds or spins a bit so you must attach it crooked a bit and plan on the unwind to get straight again. I have this drawn on my wall-the right amount of cut to spin straight.

The teapot is our most advanced form and  the making of one takes the most time. All the eleemnts must come together. Your english style with clay handel is a classic shape.

As your noted the spout must be high so it can be full and not leak out. One trick I learned in the 70s was to put just a small film of butter under spout lip as this makes the water resit dripping back down.I'm taking the smallest amount (non visible )

If that sharp edge has very little glaze on it this also helps with a no drip.

welcome to the teapot challenge world-its not for the weak of heart

Edited October 8, 2022 by Mark C.

[Hulk]

Detail:

The flanged lid style stays put all the way to the last bit of pour without falling off.

The spout is thrown on the wheel, however, as it set up, was cranked over* with a rod fitted through the hole.
From there, the channel shape was polished and elongated once the spout was mounted and cut.

No glaze on the cut edge of the spout, trying for the "wettability" gradient at the edge that Mark mentions.

The untwisting Mark mentioned, this spout is overcompensated a bit (I throw clockwise).
The spout test project should then include untwist measurement, hmm.

I pour in, pour out the liner glaze;
wax, then cut a sharp line at the outer rim edge, then sponge away excess;
and dip the outside upside down. Any beaded up drops, a small sponge sweeps up, np.
All that to say this - a little wad of clay in the spout end and covering the cut edge worked well to keep the green glaze out of the spout and off the cut portion.
The liner glaze has to be dry-oh, however, and fix the clay, dip, then gently remove the clay soon as - when the slick sheen has died off - so, within a minute or so, else the clay wad might pull away some liner for you to fix, heh. Waxing kinda fixes that.

*learned that from someone's post on this forum, imparting the spout's curve/lean early on, using a chopstick/wand/brush handle that fits through the small hole; seems to work better than trying to shape from the other end later on

 

Edited October 8, 2022 by Hulk
oops

[GEP]

Here are my latest teapot spouts. I am handbuilding them now, in order to eliminate the twisting that happens with thrown spouts. I find that the best prevention of dribbling comes from making the lower edge of the spout lip sharp, and also curving it downward. If a drop of water is clinging to the lip, it has to fall off into the cup. It can’t slide down the outside of the pot without first traveling upward, which gravity will prevent. 

 

[Pres]

While teaching at the HS I had a handout for teapots. . . .as my advanced classes had to make one for a MP benchmark. I had it posted on my blog

 

 

best,

Pres

[Hulk]

This article* might be "the latest" on the subject:

Physicists say they’ve finally solved the teapot effect—for real this time | Ars Technica

where a case is made for the "teapot effect" being related to the flow rate.

To me, it says when the liquid is flowing fast enough to "detach" from that lower edge, there's no dribbling; when the flow rate isn't fast enough to cause detachment, there is dribble.
Hence, design such that
  a) the flow rate required for detachment is lower,
  b) and the transitions between no flow and high flow (and high to none) are very quick.

Seems to me there's still work to be done to share the findings in everyday terms for practical application, heh.

*Actually, the article refers to the latest (link below), which I'd rate as a challenging read:
Developed liquid film passing a smoothed and wedge-shaped trailing edge: small-scale analysis and the ‘teapot effect’ at large Reynolds numbers | Journal of Fluid Mechanics | Cambridge Core