The article describes the study of the effects of heating and moisture removal on the chemical and physical properties of untanned and chrome tanned hide substances. Apparatus incorporating an electronic strain gauge was constructed for measurement of thermal stability (dry shrinkage and wet shrinkage temperature) of calfskin; commercially chrome tanned mechanical leather (over 10% chromic oxide) and kangaroo tail tendon fibers were also included in some tests. Nitrogen determinations (Kjeldahl chemical analysis) were done to check on thermal decomposition. Moisture determination was performed using the solvent distillation method from hide powder, untanned (depickled) and chrome tanned calfskin; a range of temperatures of 50-164°C was achieved with cyclopentane, hexane, benzene, methyl cyclohexane, toluene, ethyl cyclohexane, xylene, cumene, and mesitylene. Vacuum oven drying provided additional information. The results are explained in terms of chemical and structural changes occurring in the collagen on hydration and dehydration, and the effects of the tanning process, specifically: the existence and nature of bound water; relative heat stability of untanned and chrome tanned skin; and possible mechanisms in shrinkage and in tannage (fixation and/or chemical reaction of chrome tanning compounds with skin protein).