Hello, I'm a grad student and I'm currently using a QCM to measure solvent uptake in swelling polymer films. I'm getting some odd data where once the film swells and the QCM responds to the added mass, the frequency then starts to increase. I noticed that in your video, after adsorption occurs you start to see an increase in frequency as well. Other than temperature, solvent vapor concentration changes, or desorption of mass, what could cause an increase in the QCM crystals? I exclude these things because I'm fairly certain all of them are accounted for. Also, these increases in frequencys are on the order of 1000s of Hz on an unpolished 6MHz gold electrode crystal. Thank you for any assistance you can lend.