Why do teapots dribble?
French scientists say it’s all about the simple subject of surface wettability The teapot dribble effect could be made a thing of the past, say French scientists, who it has to be said come from a country of coffee drinkers. Photograph: Graham Turner For those who hate tea stains on their pristine linen tablecloth, succour is at hand: scientists in France have solved the perennial puzzle of the dribbling teapot. Fluids experts at the University of Lyon have produced a four-page report [pdf] that claims to offer a solution, and as often can be the case with long-unresolved problems, it is a simple one. “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 separat
