The thermal response of parchment to hygrometric chan

When parchment and leather are subjected to humidity changes there are corr esponding changes in temperature due to the gain and loss of water. This pa per examines, refines and applies to parchment a thermal technique previous ly used for the analysis of the condition of historical leather. The magnit ude, duration and decay of the thermal response of modern and historical pa rchments have been determined. The thermal response for historical parchmen ts is different to those which are modern. Generally, relaxation times are slower for rehydration when compared to dehydration. Historical parchments are gradually changing from a collagen like structure to a more gelatin-lik e structure. No significant changes in thermal response was observed within an artificia lly aged set of modern parchments using this technique. This suggests that artificial ageing does not reproduce all of the changes found in historical parchments. The thermal response and thermal decay half-life of leather is much smaller than that of parchment on a mass per unit area basis.