Quantitative Automatic Non-Invasive Assessment of Material Degradation in Historic Tapestries

Abstract

The conservation of historic tapestries is crucial due to the fragility of their materials and their cultural relevance. This paper reports on an investigation into the development of HeriTex, a non-invasive, innovative system for evaluating the structural integrity of historic tapestries, with a particular focus on measuring material loss. The research analyzed the relationship between transmitted infrared radiation and the weight loss per unit area (expressed in g/cm2) in the weakened areas of the tapestry. As a necessary first step, the system was calibrated using a limited range of wool thread weights before conducting experimental measurements on a historic tapestry fragment provided by the Royal Tapestry Factory in Madrid. The investigation demonstrated a strong correlation between the transmittance values and the loss of material weight per unit area. The results showed that the transmittance decreases exponentially as the weight per unit area increases. By applying a non-linear least squares (NLLS) fitting model, additional weight per unit area values in the tapestry were estimated based on their corresponding transmittance values. The HeriTex system enables the identification, quantification, and mapping of damage regions, demonstrating its potential as a valuable tool for more accurate assessment of the condition of historic tapestries by providing quantitative data on their structural integrity.