Magnetic resonance images of coarsening inside a foam.

Coarsening in three-dimensional polycrystalline systems such as foams, magnetic bubbles, metal crystals, and ceramics is poorly understood because of the absence of data describing the interior of these materials. We introduce magnetic resonance imaging to probe the interior of a foam, providing information on topology and foam drainage. The foam does not appear to coarsen in a self-similar way during observation periods of up to 50 h, representing over a decade of growth in the mean length scale.