Three-dimensional fluorescence analysis of bloodred webcap (Cortinarius sanguineus)-based dye on wool dyed with...

This work focused on understanding the influence of dyeing methods and dye origin on the fluorescence spectra of wool yarns dyed with bloodred webcap (Cortinarius sanguineus), and exploring the potential and limitations of non-invasive fluorescence spectrometry in differentiating natural dyes on wool textiles. Wool fibers dyed with bloodred webcap specimens from five different geographic origins or with emodin standards, and using nine different mordanting procedures, were investigated using three-dimensional (3D) fiber optic fluorescence spectrometry, resulting in a dataset of 20 excitation-emission matrices (EEMs). In addition, the effect of self-absorption on EEMs of this dataset was investigated. The ability of the fluorescence-based method to discriminate dyes from different taxonomic families was also assessed by combining the bloodred webcap data with EEMs from a more diverse dataset which includes 18 different species. The dyeing method had some effect on the collected EEMs, potentially complicating the identification of a dye source in a historical textile if the mordanting procedure is unknown. The geographic origin of the fungi samples in this dataset showed minimal impact on the fluorescence spectra. Principal component analysis of a more diverse set of EEMs was helpful in differentiating dye taxonomic families, indicating utility of fluorescence spectrometry in qualitative determinations of some natural dye sources. While fluorescence alone may be insufficient for the unequivocal identification of natural dyes, this non-invasive, non-destructive, and rapid technique can provide useful additional information for identification when used in combination with other analytical techniques.