New approaches for the analysis of dyestuffs in historical textiles by liquid chromatography and desorption electrospray ionisation (DESI) mass spectrometry: applications to Renaissance embroideries and late nineteenth century textiles
The analysis of historical dyestuffs plays a central role in the understanding of the socioeconomic context of textile production while also informing strategies for the display and preservation of museum objects. Chapter 1 presents a summary of the most important dyes and fibres together with analytical challenges unique to the field of historical dye analysis. The main analytical techniques used in the field, including both invasive and non-invasive as well as destructive and non-destructive techniques are also discussed. Emphasis is given to the need for the development of more reliable, efficient, and ideally minimally or non-invasive analytical approaches for historical dye analysis. The material and methods used are shown in Chapter 2 while the high-throughput, small-scale sample preparation method and short analytical time UHPLC-PDA method developed are described in Chapter 3. The entire workflow from extraction, filtration, drying and reconstitution strategies as well as the UHPLC-PDA separation were evaluated using nine flavonoid and anthraquinone chromophores. The method was applied to a set of 85 reference samples covering 12 dye sources and a case study of the wedding tartan of Flora MacDonald from the West Highland Museum. In Chapter 4, the workflow is applied to important examples of Scottish and English embroideries dated from the mid-16th to early 18th centuries housed at National Museums Scotland (NMS). The significance of the collection is contextualised through discussion of embroidery in Tudor and Stuart Scotland and England. The analysis of 26 objects spanning from professional clothing to domestic furnishings show that similar materials was accessible to all types of embroiderers. The range of dyestuffs identified; from locally sourced lichens to imported cochineal demonstrate that embroidery was already by the 16th century, a craft dependent on global trade. The study also showcases the efficiency of the method applied to over 250 samples. The development of non-invasive, minimally destructive desorption electrospray ionisation (DESI) mass spectrometry for the field of dye analysis is presented in Chapter 5. The design and construction of the source are outlined, alongside optimisation of geometric parameters using silk and wool samples dyed with rhodamine B. The feasibility of the application of DESI-MS to textile analysis was evaluated on natural and early synthetic dye references and successfully applied to the study of late 19th century historical samples.