Re: Why do some teapots dribble when being poured?

Hello Alison,

nice to hear from someone from my hometown of Southampton, and what a 
lovely question. 

So, why does your teapot drip? You guessed right when you said it was 
something to do with the flowrate and the shape of the spout, and I'll 
explain why.

Have you ever wondered why a golfball has hundreds of tiny dimples in it? 
It's to let it flow through the air unhindered. When the air flows around 
the ball, it would like very much to stick to it until the last minute, 
but the dimples 'shake' the air off and reduce the aerodynamic drag on the 
ball. That troublesome layer of air is called the 'boundary layer'. What's 
that got to do with pouring tea? When you pour tea, the same thing 
happens. A layer of tea flows along the bottom inside of the spout and 
upon exiting, would rather stick to the surface. This layer runs around 
the rim of the spout slightly more than the rest of the flow and loses its 
grip on the rest of the tea. It plummets sadly to the table. This does not 
mean that you should now hammer lots of little dimples in your teapot. 
High speed air has little else in common with hot tea.

Pour tea quickly, and the fast moving flow has enough momentum to break 
free of the spout and continue in a straight line (just like a fast car 
breaks free of a bend and crashes off the road). However, this usually 
causes the cup to overflow so it's not a good solution. The stainless 
steel pots that you find in motorway service stations have a sharp edge on 
the spout and the tea breaks free with very little problem. China pots 
have a texture about them and a curved edge that lends itself to 'sticky 
tea'. Try filling the pot only halfway. Then when you pour it, the spout 
will be pointing downwards slightly more than normal, drips will head more 
towards the cup, gravity will help the flow, and the inclination of the 
curve on the rim of the spout will have less effect. Had you not noticed 
that it was only the first cup or two that dribbled?

Strive to find a non-dribblesome teapot. It's nice to know that some 
people still use a teapot as opposed to just putting a teabag in a cup 
which is very unsociable. Milk, but no sugar in mine, and a couple of 
biscuits - you can pour, thank you.

Enjoy,
Justin Roux