The rehydroxylation dating method of archeological fired-clay artifacts relies on the reliability of the (time)(1/4) power law model considered for long-term moisture expansion and mass gain in ceramics. Here, we reanalyze different moisture expansion datasets that were previously used to verify this model. We show that these data obey an accurate (time)(1/N) power law, but they reveal a variability in the values of the exponent 1/N between similar to 1/2 and similar to 1/4. It is possible that this value is an intrinsic property of ceramics, naturally varying between a behavior governed by a Brownian process (t(1/2) power law) and a behavior controlled by a one-dimensional diffusion process (t(1/4) power law).