# The Teapot Effect: Why Teapots Drip

Joseph B. Keller is an immensely distinguished scientist. Professor Emeritus in engineering and mathematics at Stanford University, he may be known best for the Geometrical Theory of Diffraction and the Einstein–Brillouin–Keller method.

But his major work – honored with awards that include the National Medal of Science and the Wolf Prize – might not fully convey Dr. Keller’s sense of playful enthusiasm and perpetual curiosity.

What sparks the curiosity of a man who has attended lectures with Einstein and partied at Heisenberg’s house? For one, Joseph Keller is into teapots. Really into teapots. In fact, he is the world’s recognized expert on why teapots drip.

Like many of us, Dr. Keller had long observed the pesky problem of that little bit of tea that always seems to run down the outside of the spout and drip into our laps. “Then, in 1956, I heard a lecture,” he told me. “An Israeli scientist reported he asked 100 physicists why teapots drip and they all said it was due to surface tension. This scientist did some experiments that proved it couldn’t be caused by surface tension, so what is the explanation? I wrote a paper, ‘The Teapot Effect,’ shortly thereafter, showing that the effect occurred through fluid and mechanical forces.”

Dr. Keller showed that it was air pressure, not surface tension – that causes drips. “It is simply that at the pouring lip the pressure in the liquid is lower than the pressure in the surrounding air,” he said, “so air pressure pushes the tea against the lip and against the outside of the spout.”

In 1999, he and his colleague Jean-Marc Vanden-Broeck described the final act in the drippy teapot scenario when they calculated where gravity makes the drop fall off the pot. For this, Keller won his first Ig Nobel Prize Award from Harvard, which celebrates the unusual and imaginative in science. (His second Ig Nobel Prize was awarded in 2012 for calculating why a jogger’s pony tail swings side-to-side while her head is moving up and down.)

Can Dr. Keller look at a collection of teapots and make a reasonable guess at which are more or less drippy? “Yes, I believe I can,” he said.

He told me there are three things that help make a spout drip-proof. “The first thing is this,” he said. “If the teapot spout points up and then straight down at the pouring end, then the tea will flow back into the pot when the pot is turned upright again and a drip would be almost impossible.”

“Number two is this,” he said. “If the lower lip of the spout is sharp, as is the case with metallic teapots, then the trouble is ameliorated. The sharp edge would help prevent the tea from turning the corner. It’s still possible to drip but less likely if the tea is coming with any force. There are little metallic tools with sharp edges that fit over the end of a teapot spout that can covert a bad spout to a good one.”

His third piece of advice for avoiding drips is not to have the teapot too full. “Tea from a less full pot will flow with greater velocity. The faster the flow, the less likely it is that the tea will cling to the lip.”

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Fundamental forces in our universe make teapots drip, the same forces that make life itself possible. So if we found ourselves in a universe where no teapots ever dripped, is it possible we might not be able to survive there to enjoy the tea?

Dr. Keller chuckled at that idea. “The best I can tell you,” he said with full scientific rigor, “is maybe.”

Karen Brown is an award-winning designer and creative director of the Center for Ecoliteracy. Her work has been included in the Smithsonian Institution and Cooper-Hewitt National Design Museum, and featured in The New York Times, Architectural Digest, House Beautiful, and on Today on NBC. She believes that the handmade movement is a fundamental force for transforming society and the economy.

• from MegansMenagerie says:

Beautiful teapots!!!

141 days ago

• from LittleWrenPottery says:

Very funny article! I must admit I have my on teapot collection, they're very moreish!

141 days ago

• from EdelweissPost says:

Teapots always remind me of Beauty & the Beast's Mrs. Potts, one of the kindest of all Disney characters. I always thought tea pots dripped because I had a bad teapot! Now I don't feel so unlucky knowing EVERYone has this problem. ; )

141 days ago

from mtraub says:

When I pour from a well-designed teapot, the easy flow serves as foundation to the meditative ritual. Love hearing this scientific approach to life's subtle forces.

141 days ago

• from lauraprilltoo says:

"...So if we found ourselves in a universe where no teapots ever dripped, is it possible we might not be able to survive there to enjoy the tea?" Interesting question...as a tea lover, my question would be, would it be worth surviving in a world without tea? Amazing constellation of teapots :)

141 days ago

• from NattyMatty says:

Love it!!!

141 days ago

• from LivingVintage says:

Amazing work and story! Love the pufferfish teapot.

141 days ago

• from SylvieLiv says:

These are the neatest teapots I've ever seen! Love them! :)

141 days ago

• from AntwarePottery says:

This is why well designed teapots have a hole in the lid. I have to look up his paper. I too love teapots. Especially making them.

141 days ago

• from JewelMeShop says:

Great article! I love the hand painted teapot. It's unique!

141 days ago

• from onionbagel says:

Probably the best article ever published on Etsy.

141 days ago

• from BellaBboutique says:

They are the smallest and the most seemingly simple inquiries which astonish us at the complexity which they may be founded. Why does a tea pot drip, why does a pony tail swing side to side on a jogger, it's the simplest things which sometimes arouse the greatest awes.

140 days ago

• from 1509Partridgeberry says:

Lovely teapots, lovely science!

140 days ago

• from GluskDesigns says:

All this time I thought it was me!

140 days ago

• from SpecialTeaandSpiceCo says:

All stunning teapots. I think the one which looks like a tree stump is my favorite.

140 days ago

• from CraftUnikat says:

Oh, thank you so much for the feature in the best blog post ever! Teapots are just more than words...They are cute portals into magical time and space.

140 days ago

• from atelierOKER says:

I always try to make a not dripping teapot, but now I understand it's hardly impossible. I love your article Karen.

140 days ago

• from OhFaro says:

What a great little story. I had no idea. Thanks Karen.

140 days ago

• from minouette says:

Physicists are always getting caught up in the beauty of explaining everyday mysteries as much as those more obviously central to the field. Thanks for an enjoyable post! I enjoyed it as a physicist, artist and tea drinker.

140 days ago

I usually focus on having a sharp edge on the bottom edge of the spout to prevent the drips. From my experience making teapots it's seems to have been the main key in cutting the stream of fluid so it doesn't roll around the tip of the spout. This article gives some nice extra insight. I think pouring technique can also be helpful to avoid drips. When the cup is nearly full, quickly tilting the pot back while pushing it in the air forwards towards the spout seems to aid in tea getting pulled back into the pot. Thanks for featuring one of my dreamer teapots!

140 days ago

• from vitrifiedstudio says:

i learned something new from reading this! thanks

140 days ago

• from blkynphoto says:

what a fantastic article! I am just learning how to make a teapot after many years making ceramics and this was both insightful and really sweet! Thanks for sharing.

140 days ago

• from HudsonBlueArtisans says:

Great article, love it.

140 days ago

• from mazedasastoat says:

Now, this is exactly the type of thing that makes science worthwhile! Wonderful selection of teapots by the way!

140 days ago

• from BlueSkyPotteryCO says:

As an artist who makes ceramic teapots, I loved reading the science behind why a teapot will or will not drip. We are taught to have the spout higher than the top of the teapot and making the edge as sharp as possible to cut off the liquid. Thanks for the other tips and ideas!

140 days ago

• from travelwanderings says:

An an avid tea drinker and an engineer, I find this article both fascinating and entertaining! Dr. Keller seems down-to-earth, and I love how he uses a scientific approach to explain everyday phenomenon. A wonderful article!

140 days ago

• from JDWolfePottery says:

140 days ago

• from ikabags says:

I love your article Karen ! Thanks for beautiful post !

140 days ago

• from paulawestpottery says:

Great article. I will keep on my quest to make a dripless spout. Thanks!

140 days ago

• from WhimzyThyme says:

I love drinking tea and collecting wonderful teapots. I am so honored to be part of the wonderful article and fabulous collection. Thank you so very much Karen. I so appreciate you.

140 days ago

• says:

I'm a coffee drinker, truth be told, but I still find this article fascinating. Thank you , karen!

140 days ago

• from PatsPottery says:

LOVE this♥♥ I try out all my tea pots for drips before I sell them:>)

140 days ago

Fascinating fun to learn the science behind the pour and view many wonderful teapots. Thanks!

140 days ago

• from CedarPocket says:

Excellent article in every respect. Science plays such an important role in even the smallest everyday matters. It brings richness to life to know how things work. Thanks!

140 days ago

As part of a family of tea drinkers, this article was very interesting to me & now I know what to look for when trying to find less drippy teapots. Thank you for including all the lovely teapots, I think I found one for my mom, my sister & myself. ~ Catherine

140 days ago

• from blueroompottery says:

Fascinating!! Hmmm, I never noticed that little detail! I will make a few tea-pots as a result of your post, and see it in action! Thanks for the great article, and the beautiful tea-pots you featured! I especially love the one with the octopus handle and the ocean theme :)

140 days ago

• from Waterrose says:

Some of the creativity in the making of these teapots is amazing! What a beautiful art form.

140 days ago

• from PrayerNotes says:

Great article and fabulous teapots!

140 days ago

• from CraftyCalista says:

Love the article - thanks for the solution!

140 days ago

• from Aristocrafts says:

Beautiful article! They say mathematics and music have a lot in common, and here is another example of science and tea being closer to one another than one could imagine. Thank you for this interview, I enjoyed reading it very much... while having my cup of tea :).

140 days ago

• from naturametallum says:

140 days ago

• from TheCrochetCafe says:

Very interesting, I love all the teapots!

140 days ago

• from LASpottery says:

cool article!! I knew about the sharp edge, works for pitchers & creamers too! Amazing teapots in this article!

140 days ago

• from potterybyAnita says:

I was pretty fearful to make my first teapot, 25 years ago, since my teacher had said it's the "epitome" of being an excellent potter. But, once I tried, I found I have quite a knack at it. I even make then pretty teeny, about 1/2 inches long by about an inch tall. And, yes, turned in three pieces, with my fingers, just like the larger ones. Body, Spout and Lid, then put them all together! It's fun! ♥♥♥

140 days ago

• from DaisyandFlorrie says:

Love it when science and art meet!

140 days ago

• from TimeNSeasonTreasures says:

Intahresting...veddy veddy intahresting..;)

140 days ago

• from potterybyAnita says:

I love teapots and tea! I especially enjoy challenging myself making them, even teeny tiny, turning each piece on the pottery wheel with my fingers! ♥♥♥

140 days ago

• from pattonpottery says:

140 days ago

• from dorothydomingo says:

I must admit when I've made teapots my main emphasis has been on the design - making the spout, feet, lid, body and handle work together in an artistic way. A functional spout without drips was just a little too intimidating! I don't feel so bad now that I learned a lot of teapots drip. I may give a functional rather than sculptural teapot another go!

140 days ago

• from MaryCarolPerez says:

But, don't forget that the very best teapot might drip, just like a fine bottle of wine...

140 days ago

• from TheJoyofColor says:

Oh Love this article its one i can share with my hubby : Thank you Karen and Professor Keller

140 days ago

• from Runningpuma24 says:

I remember reading that paper in grad school... i love that it found its way onto Etsy!

140 days ago

• from ArtyDidact says:

Haha, funny! I thoroughly enjoyed this article, thank you so much for writing it. And how amazing that you even thought to ask the question! Delightful teapots, too, btw.

140 days ago

• from CreativityHappens says:

I love this!! Thanks for the great article!

140 days ago

• from HappyValleyHerbs says:

Ok... Now I have to go check! I don't think I ever notice that a teapot drips! LOL

140 days ago

• from HoneyThistle says:

I've always hated the dripping from teapots, now I can figure out which ones to buy to avoid this problem! Thanks etsy ;)

140 days ago

• from InglesidePottery says:

Great article!

140 days ago

• from Nikifashion says:

Great copper teapot!

140 days ago

• from butikonline83 says:

140 days ago

• from PaintingsByKEGilmore says:

One of my New Year's resolutions was switching from coffee to tea. Thank you for the informative article. Also: the pufferfish teapot is amazing!

140 days ago

• from SippieWine says:

Thanks for posting this great article. Food for thought. And I very much appreciate you featuring my shop!! It's inspired me to have a teapot sale! The Heath Teapot is now on sale. Happy New Year!

140 days ago

• from MaruMaru says:

wow these are so cool!

140 days ago

• from slathered says:

This is so nerd-awesome, I can hardly handle it. Thank you for such an interesting piece (and lovely teapots).

140 days ago

• from fivetenfifteen says:

i just set my drippy teapot on a tea towel. {i mean, isn't that why we have tea towels?}

140 days ago

Dripping teapots are irritating! I finally figured out it's the less expensive and novelty pots I own that are the ones not designed properly. A well designed pot feels good and is a pleasure to use, they become the go-to pots. Thanks for the article, enjoyed it!

140 days ago

• from LennyMud says:

Loved this article! Interesting to understand the mechanics while appreciating so many different aesthetics. Thank you so much!

140 days ago

• from EyeCandyandMore says:

Ha !! How much fun this blog was to read !! I drink and serve tea several times a week. I own about 47 teapots. If I find one I really want, I ask if I can try it first because the flow of the tea from the spout to the cup is very important to me. The tea must come out in a perfect stream or I won't buy it. I served tea tonight actually, and filled my pot three quarters full to make four cups. I did notice that after pouring the first cuppa one drop dripped.. It didn't happen again after that first cup. I usually try to give the pot a quick lift to avoid the drip and sometimes it does work actually.. lol.. I totally enjoyed this read.. it was lot's of fun.. ty

140 days ago

• from kittenkagome says:

Cool info. The more you know...:P

140 days ago

• from Rail19 says:

Lovely designs and structures, and creative blog post! WOW Shirley! 47 teapots is quite the collection.

140 days ago

• from PopLoveHers says:

Amazing! I love the fact that the world expert on teapot drips was inspired by an Israeli scientist too! (yes, a little patriotic pride is dripping out of my spout here too) It's amazing how such a little thing like a teapot's drip can be so closely intertwined with the grand forces of the universe that hold everything together. I say that's a perfect call for a cuppa!

140 days ago

• from SharsClayWorks says:

Wonderful article and collection! I am honored that you included mine! I love making teapots and I can't wait to get back on the wheel for my next series! :) Thank you.

140 days ago

• Such nteresting blog post - thank you Karen!

140 days ago

• says:

What a wonderful article and such a unique insight from a very interesting man! This is an article I will be re-reading. :)

140 days ago

• from FreshFromtheFlame says:

Great way to get my mind working first thing in the morning, considering the mechanics of a drip free teapot!

140 days ago

• from Tjossem says:

What a fun article and just the way to make teapots come alive for people! Many thanks.

140 days ago

• from BuckRunPottery says:

Thanks Karen!

140 days ago

• from ClayLickCreekPottery says:

This is one of the better articles I've read on Etsy. I love and appreciate the scientific reasons behind dripping or not.

140 days ago

• from OriginalBridalHanger says:

Amazing! I really love the pottery....

140 days ago

• from akatale says:

another great article! Thanks!

140 days ago

• from MotherLark says:

Love this article. It is perfect weather here for a cup of steaming tea!

140 days ago

• from allstarorganics says:

It's inspiring to see so much scientific rigor and aesthetic exuberance lavished on a common, everyday object. If only we invested this much attention on everything in our environment. I can only imagine it would improve the function and beauty of everything we make and use.

140 days ago

• from KirasPotshop says:

Thank you for featuring my Brass Knuckle Teapot! I'm flattered. The article is refreshing-- there are too many drippy teapots out there.

140 days ago

• from KirasPotshop says:

Also, teapot spouts are really tricky, even if you've been taught the "right way" to make them. The trick is making sure the spout has a larger base in comparison to the opening of the spout, and the end of the spout should form a straight channel-- for example, geometrically conical spouts aren't the answer because the water isn't channeled and when it leaves the spout the stream will probably gush out because the fluid is being channeled to a smaller point than is necessary. Trumpet spouts are also problematic. If the spout dramatically flares out at the end, or gets wider than the narrowest point, the fluid will gush out unattractively, no matter how sharp the lip of the spout may be. The opening of the spout should be the narrowest point, but there should be a "straightening out" section to redirect the water in a fluid stream, and then the lip of the spout should be crisp. Hope this tip helps teapot adventurers :)

140 days ago

• says:

Yes, Sharon, it was pretty "nerd-awesome" to talk to Dr. Keller. He was very generous with his time, and stopped frequently to ask, "Do you understand?" as he explained the Teapot Effect. His patience and clarity reminded me of what makes a teacher exceptional. And I cannot possibly tell you how much fun it was to shop for teapots on Etsy. So design-rich, experimental, and adventurous! So much variation, all in service of the perfect pour.

140 days ago

• from MaryOMalleyCeramics says:

Such a great article! Honored to have one of my teapots included!

140 days ago

• from shepherdsgrove says:

What a great article - Dr. Keller is a very interesting man and I love that he's taken such a big interest in why teapots drip :) Thanks so much for including my Australian Shepherd teapot.

140 days ago

• from ThePillowStudioShop says:

I loved reading this (and lifelong passion is always inspiring, no?) And, the teapots you featured are great! I thought I found my favorite and then would see the next and have a new favorite. It is a fantastic, original selection of teapots. Thanks!

140 days ago

• from BijouxOdalisque says:

Great article Karen! I don't know where you find these fascinating people but I want to collect them all! I plan on getting out my Grandmother's teapot collection today - you know what I'll be doing :)

140 days ago

• from gotowrist says:

Such a great tea pot! A interesting blog post!

140 days ago

• from GracefullyGirly says:

I LOVE tea and I'm a scientist at heart so it's fabulous to hear the science behind this simple tea event. That starfish sea bramble tea pot is simply amazing!!!

140 days ago

• I feel so Happy when I read about Keller's sense of whimsy With science ... YaY ! Thank You Karen, another Great interview!

140 days ago

• says:

I am very interested in teapots and this article. Thank you for sharing. I hope to make mention of it on my little blog page referencing it back to here. I am not writer of any calibre!

140 days ago

• A brilliant piece! Simon Leach also gives some very useful tips on how to construct a non-drip spout - worth checking out if you're a teapot maker. Thank you for including our teapot in such good company!! all the best, Cecilia & Eyal

140 days ago

• says:

It's so interesting to hear the different design strategies that echo the Teapot Effect. For example, AntWear, the hole in the lid is probably connected to the idea of using air pressure to force the tea out, similar to filling the pot only part way. And Kira, the narrowing of the spout that you so beautifully describe probably increases the velocity of the tea and therefore decreases the likelihood of a drip. It's so interesting to hear how observant craftspeople have solved everyday problems through responsive design.

139 days ago

• from MonicaBags says:

Great article, Karen. It's both informative and adorable — from Keller to your tea pot selections!

139 days ago

• What an interesting and informative article for those wishing to balance function and aesthetics. I'm honored to have my teapot feature in such a great article!

139 days ago

• from iammie says:

Beautiful!

139 days ago

• from EurekaGuides says:

Love this! Thanks so much. I learned a lot.

139 days ago

• from PattiTrostle says:

Great article and beautiful teapots!

139 days ago

• from FlowerMoundEscape says:

I have loved teapots since I was a little girl. They remind me of a time when things were a bit simpler even though there was more formality. This article proves that I'm not the only one that has ever wondered over this tiny little detail. Far superior minds than mine have taken the time to study it, so maybe I'm not as crazy as my husband claims! Thank you for proof!

139 days ago

• from MagpieQuilts says:

So now I finally know why the teapot drips! Thanks!

138 days ago

• from NativeStrands says:

Interesting teapots!

138 days ago

• from BambuEarth says:

So interesting. It totally makes sense once someone does all the work to find out why. ♥

138 days ago

• from BunnysLuck says:

Now....can the good doctor explain why, when you snap a piece of uncooked spagetti, there is always a little chip that snaps off and goes flying through the air? I know the folks at MIT were looking into this - seriously! - but I don't think they came up with a definitive answer. It's up to you Dr. Keller!

138 days ago

Yay science. I have loved science ever since I was little and my dad was reading Christopher the Mouse books to me and my sister. :)

138 days ago

• from Heirrahome says:

Great article. Thanks for featuring my shop!

138 days ago

• from nicolesweavingart says:

As a person who collects handmade teapots, the pictures above made me have a spasm. The good kind!

137 days ago

• from LostInTheValleyPhoto says:

I also have a teapot obsession! What a fun blog post!

137 days ago

• says:

I have a small ring with fabric on the inside, that stops the drip from running down the side of the pot. It's not the perfect solution, but it gets rid of some of the problem. And it is painted like a ladybug!

137 days ago

• from KaransPotsAndGlass says:

As a potter who has made countless teapots over the years, I found this right on. My biggest concern on teapots and pitchers too, is the sharpness of the angle on the outside, to encourage a quick "cut off". Rounded edges in my experience, drip every time. Same is true of a pitcher spout. I also concentrate on the flow of the liquid from the pot, so it has a quick flow up a channel to a quality pouring spout! :-) I'm big on quality handles, and quality spouts! No detail is too small!

137 days ago

• from TheBeautyofBoredom says:

These are all absolutely amazing!!! Thanks for sharing this story.

136 days ago

• from 27thAVE says:

Interesting article along with a lovely collection of teapots for viewing. What's not to like! Terrific Treasury! Thanks for including my teapot in your lovely collection.

136 days ago

• from TheMillineryShop says:

After reading why teapots drip, I no longer think I need a new thermos because that one will drip too. How did I miss this article? Even though I know next to nothing about it, surface tension just seemed too obvious. But count on those Israelis to figure it out - What a sharp bunch!

136 days ago

• from PetiteCuisine says:

So interesting, and now I have a guideline for choosing a new teapot.

136 days ago

• from AustriaBrass says:

Very cool, learn something new everyday. Thanks for featuring our teapots!

136 days ago

• from CasaAbril says:

really nice! thank you!

135 days ago

• from FreakyPeas says:

hmmmmm...........

135 days ago

• from jeansclaystudio says:

Well written article with great tips! Thanks for posting on the Etsy Mud Team thread!

134 days ago

• from FatPurpleBird says:

Next time someone blames my teapot, I say "blame science instead" ! Really interesting :)

134 days ago

• from MaryssaMoczanStudios says:

Beautiful collection of pots!

132 days ago