This study focuses on the rehydration of an amorphous powder (maltodextrin DE19) and a crystalline powder (lactose 100 M) and mixtures of these powders. The rehydration process was tracked using a Focused Beam Reflectance Measurement (FBRM) probe and a video camera. The setup allows for real-time monitoring of all rehydration steps. The dispersion behaviour of the mixtures, especially mixtures with between 40 and 60% lactose content differs from behaviour of both pure powders at an agitation rate of 600 rpm. Surprisingly, the sinking times of the powder mixtures were observed to be higher than the sinking times of component powders at higher temperatures. Increasing temperature and agitation rate improved powder wetting and rehydration. A mechanism for increased sinking time of powder mixes was proposed. Finally, regime maps were constructed to summarize the effect of mix composition, temperature and agitation rate on rehydration behaviour. This mapping approach can be used to qualitatively assess rehydration. (C) 2019 Elsevier B.V. All rights reserved.