Thursday, May 9th .....

One of the things I noticed while I was away, staying in different places, is how common dripping teapots are. It surprises me that people just accept that even expensive teapots drip and that stained tablecloths are just something you have to live with.  Surely it’s a problem that has a solution.  After all, scientists seem to be able to get grants for the most pointless research and solving the dripping teapot spout issue would have to be up there with curing the common cold. I decided I would do some research.

On a website about Transport Cafes in UK I found that dripping teapots is an endemic problem in these establishments which pour thousands (if not millions) of cups a day.  The article told the story of a British Engineering Company in Riyadh, Saudi Arabia.  This company decided to solve the problem by buying the best teapot in the world from Harrods so the head of the company flew to London to do the deal. You guessed it … it dripped too.  To try to explain what the problem is, I found a report on some research done at the University of Lyon in France.

"Surface wettability is an unexpected key factor in controlling flow separation and dripping, the latter being completely suppressed in the limit of superhydrophobic substrates," the report explains. "This unforeseen coupling is rationalised in terms of a novel hydro-capillary adhesion framework, which couples inertial flows to surface wettability effects. This description of flow separation successfully captures the observed dependence on the various experimental parameters – wettability, flow velocity, solid surface edge curvature. As a further illustration of this coupling, a real-time control of dripping is demonstrated using electro-wetting for contact angle actuation."

I hope that helps

What about other brew-time dilemmas? In 2003 the Royal Society of Chemistry released guidance on how to make the perfect cup of tea, and in 1998 researchers from the University of Bristol published a scientific formula for dunking a biscuit.

PS Simplifying the jargon in the French report, the problem is that the flow of tea from the spout has to be fast.  If it slows down, a drip occurs.  Allowing tannin to build up will help and having a slick surface is a good thing.  Or use teabags.