Image of a sample of cotton fibres under cross-polarized light.
Sophia Zweifel performing polarized light microscopy on a sample.
A pair of hand-embroidered underwear (likely from 1915–1925) photographed under UV light. The different ways materials fluoresce offer information about what they are made of, how they might be finished, and their condition.
Gennifer Majors taking a photograph of a collar under UV light.
Every two weeks these updates are provided by Sophia Zweifel, the Isabel Bader Fellow in Textile Conservation and Research. In residence at the Agnes and Art Conservation Program until the end of April 2017, Sophia is investigating historical practices of clothing care and cleaning, using the Queen’s University Collection of Canadian Dress and with the assistance of Gennifer Majors, the Isabel Bader Graduate Intern in Textile Conservation and Research.
13 February 2017
This past month, we have been performing microscopy on a selection of micro-samples carefully gathered from the first few objects of our study. Using a polarized light microscope, we are able to identify the fibre type of the sample, which gives us an understanding of the textile’s composition. Whether a fabric is made of plant-based fibres, such as cotton, or protein-based fibres, such as silk or wool, dictates how the fabric would have been cared for, cleaned, and finished. Under magnification, we can also observe the finish and how it interacts with the fibre, giving us clues as to what the finish may be. In some cases, there are tests we can perform to identify a finish; exposing a sample under the microscope with potassium iodide, for example, is a method for identifying starch (starch turns a purple-blue when it reacts with the iodine).
In some cases, microscopy is not enough to fully characterize the components of a finish. This is where having access to instrumental analysis in the Queen’s Art Conservation program has been particularly useful. We have been working with Scott Williams, a conservation scientist currently teaching in the Art Conservation program, to perform Fourier Transform Infrared Spectroscopy on the starched collars in our study. This analytical technique identifies characteristic molecular bonding structures as a way to identify a material. Using this process, we have found not only starch on the collars, but also a gum component (most likely gum tragacanth) that would likely have been added to the starch mixture to achieve a higher level of gloss on the fabric. This is an exciting discovery as it provides a physical confirmation of the historical practice of adding gums to starch that we have been reading about in our research.
While doing our photo-documentation, we also analysed our objects of study under ultraviolet (UV) light. Ultraviolet radiation is higher in energy than visible light, and is damaging to most materials under prolonged exposure. However, in exposing an object to UV for the short amount of time required to take a photograph, we can gain information about different materials based on the colour and intensity of their fluorescence. For textiles, UV examination is a useful tool to detect finishes, optical brighteners and sometimes detergent residues. It can also highlight different types of damage, such as water exposure or staining. While UV fluorescence can’t tell us exactly what a material, finish, residue, or stain is, it can provide us with clues that point us in the right direction.
As we piece together the information retrieved by all these methods, we can begin to characterize the construction, material properties, finishes, and degradation of our objects of study. This type of analysis is critical for our research into historical care and finishing processes, and will also help us as we move forward with any necessary treatments.