  In this study, we experimentally investigated the time dependence of the
statistical properties of two-dimensional drying crack patterns to determine
the functional form of fragment size distribution. Experiments using a thin
layer of a magnesium carbonate hydroxide paste revealed a "dynamical scaling"
property in the time series of the fragment size distribution, which has been
predicted by theoretical and numerical studies. Further analysis results based
on Bayesian inference show the transition of the functional form of the
fragment size distribution from a log-normal distribution to a generalized
gamma distribution. The combination of a statistical model of the fragmentation
process and the dynamics of stress concentration of a drying thin layer of
viscoelastic material explains the origin of the transition.
