Differential scanning calorimetry (DSC) allows to study the enthalpy changes which are associated with the denaturation of collagen, of which shrinkage is the macroscopic manifestation. Damage to skin, leather or parchment may be expected to manifest as a decrease of either the temperature of denaturation and/or the enthalpy changes. These modifications are associated with those of other chemical and mechanical characteristics. DSC is a very fine tool to follow in an easy way the reaction of leather or parchment to an ageing or a conservation treatment. While for leather DeltaH seems to have less than T-d, for parchment, it must be looked at very carefully since an unchanged T-d value can be accompanied by a fall of DeltaH. The case of archeological waterlogged leather is particular since the state of deterioration is apparently not correlated with the hydrothermal stability.