Thermal analysis (thermogravimetry (TG) and derivative thermogravimetry (DTG)) has been applied to study the composition of commercially available base grounds. In several samples an additional XRD analysis was required for full characterisation purposes. Thermoanalytical curves of grounds, belonging to two works of art were also carried out. The results obtained by thermal analysis were related to the nature and composition of the ground layers providing useful information in further studies on grounds used in canvas, sculpture and altarpieces.