Researcher(s)
- Levi Bielewicz, Chemistry, University of Delaware
Faculty Mentor(s)
- Jocelyn Alcántara-García, Chemistry & Art Conservation, University of Delaware
Abstract
The study of historic dye and pigment identification helps us better understand the cultures and practices of those in the past. Non-destructive research methods are key because they preserve cultural items, enabling their continued study and appreciation.
One frequently used method, diffuse reflectance, or fiber optics reflectance spectroscopy (FORS) collects molecular data about the colorants in historic pigments and textiles. X-ray fluorescence (XRF) provides complementary, elemental, information. Combining both techniques is a common practice in cultural heritage analysis. Both methods are non-destructive and relatively inexpensive. However, visual analysis of FORS spectra alone may be considered imprecise (as bands are broad), and XRF alone only provides elemental information that may indicate multiple pigments, rendering this information ambiguous.
Both XRF and FORS analyses were performed on 16th-century Spanish illuminated manuscripts (cartas ejecutorias de hidalguia); and textile samples dyed with the chromophores alizarin and carminic acid, commonly found in red historic textiles. The Spanish manuscripts contained (combinations of) known pigments and precious metals, potentially revealing new information about their historical use in Spain.
Previous research on Norwich textiles using an identical methodology and chromatographic cross-validation suggested that statistical analysis of spectral data may aid in identifying dye combinations. Performing a principal component analysis (PCA) on FORS data from the prepared sample textiles, showed clear clustering by material in the near-infrared region; and by dye combination in the ultraviolet-visible light region. This clustering indicates that ratio-determining detection of chromophores in textiles is feasible.
This method (FORS) of non-destructive analysis works and is well established, but the introduction of chemometrics will allow researchers to more precisely identify chromophore combinations and recipes in the future. This possibility highlights the importance of this cultural heritage research as it not only gives us insight into the past, but can lead to advancements in analytical techniques in the future.