Risk of climate-induced damage in historic textiles

Eleven woollen and silk historical textiles, and two modern artist canvases were examined to determine their water-vapour adsorption, moisture dimensional response and tensile behaviour. All of the textiles showed a similar general pattern of moisture response. A rise in ambient relative humidity (RH) from dry conditions produced expansion of a textile until a certain critical RH level after which a contraction occurred to a greater or lesser degree depending on the yarn crimp and the woven geometry. The largest expansion recorded between the dry state and 80% RH was 1.2 and 0.9% for woollen and silk textiles, respectively. The largest shrinkage of 0.8% at high RH range was experienced by a modern linen canvas. Two potential damage mechanisms, related to the moisture response of the textiles - stress build¬ing due to shrinkage of the textile restrained in its dimensional response and the fretting fatigue when yarns move with friction one against another - were found insignificant in typical textile display environments unless the textiles are severely degraded or excessively strained in their mounting.