The main objective of this research is to validate the application of a recently developed isometric method for determining the resistance to denaturation of leather tanned with different vegetable extracts. The results obtained for shrinkage temperature and denaturation temperature are similar to those obtained by methods based on ISO 3380 (traditional) and Differential Scanning Calorimetry (DSC). The isometric method also allows evaluating the evolution of hydrothermal breakdown of the different types of collagen (leather) – tannin (vegetable tanning extract) bonds as a function of the thermal increase to which the leather is subjected. It is concluded that, with the isometric method, and for leathers tanned with vegetable extracts, much more comprehensive information is obtained about the denaturation process of vegetable-tanned leather than with the traditional method, without requiring significant investments as in the case of the DSC method.The GREiA research group would like to thank the Catalan Govern ment for the quality accreditation given to her research group (2021 SGR 01615). GREiA is certified agent TECNIO in the category of tech nology developers from the Government of Catalonia.