Pouring viscous fluid out of a tipped container in minimal time.

Emptying a container partially filled with viscous fluid can be a frustratingly slow process. It takes time for the fluid to even begin discharging after tipping the container to develop a draining film on the interior surface. To study the effects of the shape and the tipping angle of the container, we predict the time required for the fluid to begin discharging in two simple geometries. In addition, the volume of the fluid yet to be discharged at subsequent times is predicted to decrease as t(-1/2) or t(-1) for flow driven along a plane or corner, respectively. We compare these theoretical predictions with laboratory experiments and discuss how viscous fluids could be poured out most effectively.