Measurement of shrinkage behaviour in leather and parchment by dynamic mechanical thermal analysis

The mechanical behaviour of modern and historic parchment and leather samples through their shrinkage temperature is described. The measurements are made possible by the novel modification of a standard dynamic mechanical thermal analyser (Rheometric Scientific DMTA Mk3) to enable experiments to be conducted on samples immersed in water. A sample of parchment was clamped in tensile mode under a small static applied force. The temperature of the water could be controlled and thus it was possible to heat the sample and monitor the change in its displacement as it passed through the shrinkage temperature. Information could therefore be obtained on the percentage shrinkage and the temperature range over which it occurred. Furthermore, the method also provided useful information on the expansion or contraction of the samples on initial immersion in water, which relates to ease of sample wettability, and on the changes during drying process and rehydration.