  Empirical exponents for the growth of average domain size commonly lie
between the known limits of 1/2 and 1/3. Here, a framework is developed in the
context of foams to quantitatively explain such intermediate exponents, based
on a model of gas diffusion and microstructure in which bubbles are
approximately spherical and meet at approximately circular films. This predicts
growth that is only logarithmically different from a 1/3 power law for
nearly-kissing spheres at jamming. It also predicts how the growth law and
effective exponents vary with liquid content, as set by the film radius. These
predictions compare well with experimental data for two different foaming
systems.
