The rehydration behavior of biopolymer powders was investigated. Problems that arise during powder rehydration, e.g., floating and formation of particle aggregates, are mainly attributed to the dynamics of capillary water uptake. Common methods for analysis are too slow to assess the fast changes and do not allow conclusions about causal relationships. For a more detailed understanding, relevant powder properties were investigated. Results show that viscosity development in the rehydration liquid as well as swelling, and in particular their dynamics, are crucial for powder rehydration. The dynamic capillary rise was modeled based on the Washburn equation and results were linked to the physical powder characteristics. The approach allows the evaluation, whether viscosity or swelling effects lead to a critical rehydration behavior.