We consider the nonlinear folding behavior of a viscous filament or a sheet under
the influence of an external force such as gravity. Everyday examples of this phenomenon are
provided by the periodic folding of a sheet of honey as it impinges on toast, or the folding
of a stream of shampoo as it falls on one’s hand. To understand the evolution of a fold, we
formulate and solve a free-boundary problem for the phenomenon, give scaling laws for the size
of the folds and the frequency with which they are laid out, and verify these experimentally