Understanding colour in Renaissance embroidery: new analytical approaches

Abstract

• Historical objects are often a reflection of the time they were created. Depending on the nature of the object, they can give insight into the necessities, fashion trends and mentality of the time they were used. To expand the information received from historic objects, scientific techniques can be applied, which can give us a better understanding of the contemporary knowledge, skills and even possible trading routes. On the other hand, scientific analysis of historical objects can be controversial since most techniques require the destruction of a small sample of the objects. This project focuses on the dye analysis of a collection of Scottish and English embroideries from the late renaissance located at the National Museum Scotland using high performance liquid chromatography (HPLC), ultra-high performance liquid chromatography (UHPLC) and mass spectrometry (MS). It will also try to develop non-invasive analytical techniques, such as MALDESI and spectroscopy, for application in the heritage sciences. National Museums Scotland include an outstanding group of over 30 Scottish and English embroideries dating from the mid-16th to the late-17th century. Its quality and breadth, as well as the techniques represented, make this collection of national significance. The huge variety in the possible application of embroideries and the vast diversity in producers means that each object has their own unique story, which can tell us much about the embroiderer and the owner alike and be extended to reflect the view of the society at that time. Since embroidery was as much of a domestic task as professional, studying the objects can tell us something about what materials and knowledge were available as well as unavailable to amateurs and in such a way aid our understanding of renaissance Britain. Knowing the raw material used for dyeing the embroidery threads in Scotland and England will also shine light on possible trade routes between the British Isle and continental Europe, as many sources of natural dyes cannot be cultivated in the UK. This will broaden our understanding of Renaissance Britain's communications and political position. Historical dye analysis is a complicated science due to the multiple raw material sources used for similar hues and the often-limited written record of the dye production, as most dye houses were quite secretive. It is further complicated by the different degradation processes that can occur to a historical sample over time. Since identification of unknowns within analytical chemistry is done by comparing the sample obtained with various reference samples, the lack of historical recipes means that we cannot dye exact references to use for identification. The degradation processes also mean that we need to know how conditions, such as light, pH and temperature, affect the different dyes over time to understand which signals are from the degradation products of which dyes. These signals will change depending on the history and storage of the sample, which means that a detailed understanding of the history of the object often is necessary to explain unexpected peaks. Historical dye analysis is also complicated by the knowledge that many dyers used various different dyes to create the desired hue, meaning that the data obtained will contain signals from all the dyes present and the challenge is to separate them into its constituent dyes. Developing a technique that minimises the effect of these uncertainties is one of the aims of this PhD. Developing an analytical method also means developing a sample preparation which does separate the dye molecule and the fibrous material but does not react with or degrade the obtained dye molecule is a challenge. A wrong method might lead to the complete disappearance of a dye or different dyes appearing as each other. However, the need for sample preparation will become obsolete if a non-invasive, properly discriminative method can be developed.