Understanding the hydration of the collagen historic parchments is of great importance to the conservation
and restoration processes. In this study, modern and historic (dated 1817 and 1769) parchments were
investigated using dynamic water vapour adsorption/desorption (sorption) experiments. The relationship
between the equilibrium moisture content against the relative humidity at constant temperature
for two consecutive sorption cycles, the hysteresis and kinetic properties were analysed for different
parchments from a historic archive. It was found that historical parchment samples exhibited higher
equilibrium moisture content levels throughout most of the hygroscopic range and the hysteresis was
greater than that of the contemporary sample. The samples were all found to obey parallel exponential
kinetics for both adsorption and desorption. By applying the parallel exponential kinetic model, it was
observed that the difference in the hysteresis is apparently mostly due to changes in the collagen matrix
relaxation processes.