Rediscovering the materials of Arraiolos historical tapestries: fibre and mordant analysis by SEM-EDX and μ-PIXE

Abstract

Arraiolos tapestries are probably one of the richest artistic Portuguese expressions in terms of textile heritage. It is difficult to date the beginning of the production of rugs in Arraiolos (Southern Portugal), but they were already produced in the late 1600’s as they are listed in the inventories of Portuguese aristocratic households in the beginning of the 18th century. In this work, we present preliminary results of microanalysis by SEM-EDX and μ-PIXE of fibres from Arraiolos rugs of the Ancient Art National Museum collection in order to assess fibre identification and degradation evaluation and mordant analysis by 2D elemental mapping. This study is integrated in project “REMATAR- Rediscovering the Materials of Arraiolos Tapestries” which intends to obtain detailed and systematised information on the composition and structure of these tapestries and on their degradation processes and to use these data to improve conservation methodologies. Moreover, the collected data on the dyestuffs and mordants will hopefully allow a time scale of materials usage that could assist on the dating of other Arraiolos pieces. The results on the historic samples show that linen and hemp were used for the support (warp threads) and wool for the weaving. In general, the wool fibres display the typical scale structure of wool with no obvious disruptions of morphology. However, in some cases, the wool fibres present roughened surfaces with loss of scales structure, transversal cracking and longitudinal splitting which is indicative of wear and biological degradation. With exception to blue dyed fibres, EDX analysis showed the presence of aluminium (and, in some cases, other metallic minor elements) evenly distributed over the fibres which is consistent with the usage of alum as mordant. Further quantitative analysis is ongoing to ascertain the elements source and identification of the mordants used.