Risk of Climate‐Induced Damage in Historic Textiles

Abstract

Eleven wool and silk historic textiles and two modern artist's canvases were examined to determine their water vapour adsorption, moisture dimensional response and tensile behaviour. All 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 weave geometry. The largest expansion recorded between the dry state and 80% RH was 1.2 and 0.9% for wool 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 building as a result of 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.

Methodology for tensile testing historic tapestries

“…Figure 2 also shows the tangent at the last stage of each load-strain curve. As a first observation on these curves it can be noticed that they follow the standard tensile behaviour that characterizes other textile woven samples that are found on the literature [7]. This behaviour is composed of three different stages.…”

“…This behaviour is composed of three different stages. Initially there is a zone where the samples are adjusting to the pulling grips and that is commonly known as "slack" [7]. In tested samples of Figure 2, this is a very subtle change that happens before 1 % strain.…”

“…These two methods are the tensile testing using a Universal Tensile Machine (UTM) and Digital Image Correlation (DIC). Each method has been proved to be useful in the understanding of the mechanical behaviour of tapestry structures [7,9]. However, what is now explored is the simultaneous use of these two methods in a more holistic way by characterizing the heterogeneous physical properties of historic samples by clarifying the understanding on how these complex tapestry structures behave.…”

“…However due to the fact that textiles are mechanically different from other materials [7], in this study the slope of the linear region was called the apparent linear modulus and was calculated by the slope of the linear zone in the load-strain curve as suggested in the literature [1]. Units of KN/m were used to compare results with others available in literature [1,7]. To confirm the linearity of the linear zone in each curve a linear regression line was calculated on excel in steps of 1% strain, starting from 0% until the end of the curve.…”

“…Past research studied how DIC can be used to monitor strain in historic tapestries [2] as well as how tensile tests are useful to extract tensile properties from tapestry samples [7].…”