Dripless teapot?

I've seen them advertised, but I have my doubts. I brew in the cup. Toci

A while back, someone posted the link for these:

A dripless teapot "gadget" that goes in the spout to "fix" your current pot. I haven't bought one yet, so I can't say whether they work or not.

Looks like you could make your own with an inch and a half of plastic coated wire tie.

Yes they work, 80%

It has to do with the angle of the spout at the end and very little else. I can recommend the Chatsworth pots.

--scott

Yes, the Jenaer (which ceased production at the end of March) and Bodum glass teapots have excellent reputations for being dripless. The IngenuiTea from adagio.com is popular with those who make tea at work. My Bee House teapot is dripless depending on how I pour. If I don't use quick wrist-action, a drop of tea hangs from the lip (but doesn't drop) as it does for the teapot of my Tea-for-One Brown Betty set and bone china Chatsford teapots. These are made dripless with the gadget that Derek mentioned.

The thing about spouts is that the ones with elongated openings and longer underlips pour much better compared to spout openings that are round with short to no underlips. I've got two of the latter that are so poorly shaped that not even the dripless gadget will help.

I find that most glass pots with underlips (like the Jenaer) are dripless, as long as you keep the rate of flow low enough that liquid doesn't over-run the underlip. I also use a tetsubin with a round spout, no underlip, and amazingly it never seems to drip (the most I've seen it drip is one single drop). I think with these types of pots, it really does have a lot to do with the diameter of the spout and the angle, as one previous poster mentioned.

One option is to make your current pot dripless.

Most pots I've tried this on respond well, or even perfectly. All it needs is a thin film of anything unwettable (hydrophobic; low surface-energy with no hydrogen bonding) where you want the stream to separate. An easy demo is to wipe the thinnest possible film of flavorless cooking oil around the spout, but that will wash off quickly. More serious nerds can use either Rain-X (from any auto store) or a fluorosilicone sample from Du Pont. I've tried Teflon mold-release spray, which works fine but makes a visible, powdery coating.

Now all the chemophobe paranoiacs here can start griping.

-DM

I have an inexpensive 2-cup Chatsford that doesn't seem to drip. The larger Bodum that I got years ago does, however.

All the old teapots and kettles (before ACAD design that started in early

70-ies.) are that way - they do not drip or spill or whatever. Almsot all of these things were designed by engineers. But since ACAD things started to be designed by "designers" and these people do not have adequate training in engineering and physics, so as long as the teapot or coffeepot looks good on the screen, they are OK. Now that things are designed by 3d engineering programs like Solidworks and it became even easier to do so, another disaster is everywhere - things breaking off because they are too thin (like plastic tabs on battery lids, etc. SanDisk USB memory dongle has a tiny depression with a thingy to ancor the lanyard. It is so thin that a weak tug from being caught in a jacket crevasse and it gets silently broken with your precious data laying somewhere on the floor. But I am sure that on the screen it looked very solid. But the best non-spilling teapot has the spout with down-looking opening like some of the Chinese porcelin teapots. However it only works if the internal parts of the spout is rough porcelin and has enough surface tension to hold that last single drop that forms on the downlooking part of the spout. Same design with glazed internal surface does not work as well. But even in this case the worst that can happen is that one drop of tea will spill. Some of the contemporar pots from the coffee-makers are spilling the half of the liquid everywhere but not where it is meant to be poured. Spilling pots and day-saving time are the two most stupid everyday things that irritate me immensly.

Sasha.

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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.

Neither potter nor scientist, I hesitate to raise a question I should have asked a bit earlier: Isn't surface tension a property of liquids, e.g. tea liquor, not solids, e.g. teapots?

/Lew

Yeah, the property in question is often referred to as wetting. I have no idea how much jargon surrounds that, suffice to say that a single droplet of water (or oil, or acid, or etc) on a sterile plane of a given material will take a different shape than on some other material. e.g. the same amount of liquid will cover a given amount of surface area, and there will also be differences in how it clings to it.

ST is a property of the liquid, but depending on the contcact surface it can manifest itself in different ways. Major factor would be the specific gravity of the very thin film of the material in contact or other factors that would define basically if the surface will be "phobic" of "phillic" to a particular liquid and vice versa. In the case I was describing the glaze layer on the porcelin is very light and the water is less likely to form a film on it (which would prevent it from forming a drop and dropping down). Unglazed porcelin is more dense and water wets it forming such a film.

A very good indicator of such properties is luster that can be observed by naked eye. Luster in mineralogy is one of the major properties of the material actually disclosing the very nature of the chemical bonds in it. Diamond luster is an indication of strong covalent bonds, glassy - ion bonds, melallic - free electron bonds and fatty - Van der Vaals (hydrogen) bonds. Thus you can be quite sure that a material with fresh fatty luster will be quite hydriphobic, as opposed to the material with diamond luster. The highest diamond luster is certainly a property of diamonds that are so likely to be wetted by anything even remotely liquidy that it actually can be wetted by pig fat which was used in diamond mines as the way to catch diamonds - the gravels were fed through rotating drums layered with fresh pig fat and only the diamonds would stick to it, the rest of the gravel would fall off. X-Ray flourescence is mostly used nowadays to great joy of pigs and (I am guessing) kosher Jewish diamond dealers, if there is such a thing :)

Sasha.

Interesting. So (and please correct me if I'm wrong)

- the pot drips if a drop can form where tea liquor and spout meet;

- the surface tension needed for drop formation is increased by a relatively fluffy spout lining like a glaze, while a dense material like unglazed ceramics attracts the liquid, preventing drop formation.

In the naive and sloppy part of my mind where I've accounted for this kind of thing until now, I assumed that vitreous surfaces repelled water because they were dense. But really, at the level where this stuff takes place, I suppose it's a long way between particles, so there had to be something else in play, right?

/Lew

Approximately :)

Let me put it this way - a drop of liquid has to "decide" if it rather be attracted to contact material (and then it wets it) or to itself (and then it forms some sort of spherical surface. The density of the immediate thin film on the contact surface is critical for such decision.If the desnity of such is higher than the liquid's it is likely to wet it and form the negatively curved surface. If it is lower - it will likely to form positively curved surface. A good example is ater and mercury in a glass tube. The more sperical is that positively curved surface, the taller is the drop, the more distance between the surface and the center of the drop's gravity and the more likely it will lose contact with the surface and actually drip. the bettr it wets the surface the thinner is the liquid film and the less likely it would lose contact with the surface and drip.

Not that I am aware of. I have not looked at any math models recently, but if I remember right gravitational pull plays major role in this. In some special cases like with oils ionic forces are also at play. One could have suspected also some additional molecular forces at play, especially in water, bust since all liquids are subject to this type of effect disregarding the chemistry its unlikely that such forces play any significant role in common cases.

Sasha.

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Yes. But, I'm just a poor country boy. We used to test teapots of the same size and made of the same clay and glaze formulae, and found that some poured better than others; that is, some did that pull-the-last-drop-back trick. The question for us was always, Why this one and not that one? Anyway, it's nice when you get one that doesn't drip. Nonetheless, dripless is *not* a sine qua non of a good pot in my book.

Michael

Sasha,

After reading and rereading your latest posts a time or two there is nothing left but to take a bunch of teapots, do the pour thing, and observe. Let's just see. Of course, I'd never thought of the drip patterns quite the way you describe them, but it sure does make a lot of sense.

Michael

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