Throughout the process, the sample weight is gravimetrically monitored as a function of the vapour pressure, which allows the adsorbed amount to be determined. Specifically, the sorption isotherm is determined by plotting the adsorbed mass (adsorbed mass related to the dry mass of the sample) as a function of the relative pressure. The measurement results used in this work were measured with a DVS RESOLUTION instrument from Surface Measurement Systems Ltd (SMS). Water vapour was used as the adsorbent and the isotherm data was measured at 298 K in equilibrium dm/dT 0.003.