This application note illustrates how Q-Sense Quartz Crystal Microbalance with Dissipation (QCM-D) can be used to characterize changes in film properties exposed to moist air. Measurements are easily conducted in the Q-Sense Humidity Module – the relative humidity can rapidly be changed and controlled without using other equipment. Humidity measurements are of importance in a wide range of applications, for example pulp and paper research, drug encapsulation for storage and delivery, and moisture absorption in polymers e.g. photoresists. Here, an analysis on how water uptake affects properties and thickness of different starch films, is presented.