In natural plastic clays used on ceramic compositions, the presence of certain minerals is frequently observed in the mineralogical composition. In this study, the drying ability of five different clay minerals was examined. All experiments were conducted under steady-state drying conditions. The sorption isotherm of the samples was determined by measurement of the mass of water absorbed at a fixed temperature versus the relative partial water pressure. The shrinkage of pastes was measured under the same experimental conditions. From the experimental data the heat of water sorption was calculated using a model which comes from the interpretation of a sorption reaction. The specific behaviour of the five clay minerals studied was observed; this can explain the behaviour of common plastic clays during the drying process. In particular, some investigations were conducted on mixed minerals. The results should support the possibility of obtaining a correlation between the heat of water sorption of certain clay raw materials and their mineralogical composition.