Field-Emission Scanning Electron Microscopy and Energy-Dispersive X-Ray Analysis to Understand the Role of Tannin-Based Dyes in the Degradation of Historical Wool Textiles

Abstract

An innovative approach, combining field-emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX) analysis, is presented to investigate the degradation mechanisms affecting tannin-dyed wool. In fact, tannin-dyed textiles are more sensitive to degradation then those dyed with other dyestuffs, even in the same conservation conditions. FESEM-EDX was first used to study a set of 48 wool specimens (artificially aged) dyed with several raw materials and mordants, and prepared according to historical dyeing recipes. EDX analysis was performed on the surface of wool threads and on their cross-sections. In addition, in order to validate the model formulated by the analysis of reference materials, several samples collected from historical and archaeological textiles were subjected to FESEM-EDX analysis. FESEM-EDX investigations enabled us to reveal the correlation between elemental composition and morphological changes. In addition, aging processes were clarified by studying changes in the elemental composition of wool from the protective cuticle to the fiber core in cross-sections. Morphological and elemental analysis of wool specimens and of archaeological and historical textiles showed that the presence of tannins increases wool damage, primarily by causing a sulfur decrease and fiber oxidation.

Pre-Columbian Archeological Textiles: A Source of Pseudomonas aeruginosa with Virulence Attributes

“…This finding could be interpreted as evidence of extensive destruction of cysteine in these archeological keratin fibers. Disulfide bonds are the main chemical cross-linkage maintaining the keratin fiber's secondary structure [30,31]. Cleavage of a large proportion of the disulfide bonds between its molecular chains causes a high degree of keratin degradation.…”

Preliminary Studies on the Application of Grape Seed Extract in the Dyeing and Functional Modification of Cotton Fabric

“…The earliest applications are found in the field of leather and textile processing. In ancient times, tannins were used as a tanning material of leathers [3], and a colorant for the black coloring of silk, wool and cotton textiles, where the black colors result from the complexation between tannins and iron salts [4][5][6][7]. Later, more applications of tannins were further reported.…”

A Mass Spectrometric Study on Tannin Degradation within Dyed Woolen Yarns

“…The total content for the yarns without any mordant is higher than that of the yarns mordanted with iron, at all ageing times. The presence of iron usually has a significant effect on the degradation of the textile matrix, as observed by a morphological point of view in our paper on the field-emission scanning electron microscopy (FESEM) study of the same set of reference yarns [28], as well as by the extent of photo-oxidation of the lipid fraction of wool in our paper on the gas chromatography/mass spectrometry (GC/MS) analysis of the reference set [29]. However, the results obtained in this work suggest that the presence of iron also affects the uptake of gallotannins during the dyeing process.…”