Non-invasive analysis of heritage textiles with MA-XRF mapping—exploring the possibilities. The study of Bishop Jacques de Vitry's mitres and fragile medieval reliquary purses from Namur (Belgium)

Abstract

This manuscript explores the potential of macro-X-ray fluorescence (MA-XRF) for the non-invasive analysis of heritage textiles. XRF, especially with the portable instruments, is a well-known technique for the non-destructive examination of various cultural heritage objects. It allows analysis of elemental composition based on single-point measurements. However, large, or complex textiles require numerous analysis points to identify the materials used and correctly interpret the spectra. MA-XRF takes this type of research to the next level, as it is possible to visualise the element distribution over an entire mapped area. In this paper, we discuss the application of this technique to the study of complex and multi-layered textile objects from exceptional Belgian heritage collections, including two mitres attributed to Bishop Jacques de Vitry, dating between twelfth and thirteenth century, and two of the seven extremely fine medieval reliquary purses from Namur. These are very fragile, richly decorated textile objects whose current state of preservation is a major impediment to sampling. MA-XRF mapping was applied for the identification of the elements of different materials in a non-invasive manner, including metal threads, ink, dyes, and various materials used in illuminations. In addition to material identification, stratigraphic information was obtained from the visualisation of element distributions, and hidden structural details were discovered. MA-XRF was also tested on some areas with more relief, such as the embroidery and braid made with metal threads, and the undulated multi-layered structure of the parchment mitre. Even though the analyses here could not be carried out in optimal conditions, these locations could also be analysed, albeit at a lower resolution. Finally, the technique proved very effective as a tool for screening, allowing samples to be taken at a more informative and representative location and minimising sampling.