Paul Garside

Identification of cellulosic fibres by FTIR spectroscopy: thread and single fibre analysis by attenuated total reflectance

Abstract The accurate identification of fibres is of importance to conservators, allowing the most appropriate methods of treatment to be employed. This research has concentrated on the development of an ATR FTIR (attenuated total reflectance Fourier transform infrared) spectroscopic technique for the characterization of cellulosic (plant) fibres. Six species of fibre were examined, taken largely from the bast group (flax, hemp, jute and ramie), as well as cotton and sisal. Initially, unprocessed fibres were considered; subsequently, processed fibres from a variety of sources were examined. Peak intensity ratio techniques were employed to differentiate the fibre types on the basis of relative lignin content with respect to other cellular components. It was found that, for each of the species of fibre, the ratios fell within characteristic ranges.

Characterization of Historic Silk by Polarized Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy for Informed Conservation

When assessing historic textiles and considering appropriate conservation, display, and storage strategies, characterizing the physical condition of the textiles is essential. Our work has concentrated on developing nondestructive or micro-destructive methodologies that will permit this. Previously, we have demonstrated a correlation between the physical deterioration of unweighted and “pink” tin (IV) chloride weighted silk and certain measurable spectroscopic and chromatographic signatures, derived from polarized Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy (Pol-ATR) and high-performance liquid chromatography (HPLC) microsampling analyses. The application of the Pol-ATR technique to aged silk characterization has now been extended to include a more comprehensive range of weighting methods and aging regimes. This was intended to replicate the full spectrum of states of deterioration observed in silk textiles, from pristine to heavily degraded. Breaking strength was employed as a measure of the physical integrity of the fibers, and, as expected, decreased with aging. An orientational crystallinity parameter, reflecting the microstructural ordering of the fibroin polymer within the fibers, was derived from the Pol-ATR spectra. A good correlation was observed between the breaking strength of the variety of fibers and this parameter. This suggests that the physical state of historic silk fabrics might be adequately characterized for conservation purposes by such indirect micromethodology.

Identification of cellulosic fibres by FTIR spectroscopy: differentiation of flax and hemp by polarized ATR FTIR

Abstract The ability to identify accurately natural fibres is of importance to conservators, but this can prove problematic when dealing with fibres which possess similar chemistry and microstructure – the bast fibres flax and hemp are particularly challenging in this regard. Conventional techniques, such as microscopic examination, the measurement of fibre widths and the use of the twist test, will often prove unreliable, especially when dealing with degraded materials. This research has concentrated on the development of an attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic technique employing polarized radiation to differentiate these two fibre types on the basis of the characteristic nature of the winding of their secondary cell walls: while the angle of fibrillar wind is roughly the same for both fibres (∼7°), the senses of wind are opposite – S (anti-clockwise) in the case of flax; Z (clockwise) for hemp. A crystallinity index, derived from the spectra, was found to vary in a systematic manner as the fibres were rotated with respect to the electric vector of the incident radiation. A good correlation between this variation and theoretical models was observed. It was found that the characteristic sense and angle of wind of the fibres could be determined, and thus hemp and flax distinguished.

Use of Polarized Spectroscopy as a Tool for Examining the Microstructure of Cellulosic Textile Fibers

Textile artifacts form a vital part of our cultural heritage. In order to determine appropriate methods of conservation, storage, and display, it is important to understand the current physical state of an artifact, as effected by the microstructure of the component fibers. The semi-crystalline nature of the constituent polymer aggregates, the degree of crystallinity, and the crystallite orientation have a significant influence on mechanical properties. The value of polarized Fourier transform infrared (FT-IR) spectroscopy in probing these aspects of cellulosic fibers has been assessed. A variety of representative fibers (both natural plant fibers and regenerated materials) were examined by polarized attenuated total reflection spectroscopy (Pol-ATR) and polarized infrared microspectroscopy (Pol-μIR); the former is a surface sampling technique and the latter is a transmission technique. The introduction of a polarizer into the system allows the alignment as well as the nature of bonds to be determined, and thus the presence and extent of crystallinity or long-range ordering can be investigated. Using the data from the Pol-ATR experiments, it was found to be possible to derive the principle alignment of the cellulose polymer with respect to the fiber axis, along with an indication of the total cellulose crystallinity of the material, as measured by a crystallinity parameter, χ. The Pol-μIR spectra, on the other hand, yielded more limited information, particularly when considering plant fibers with more complex microstructures.

Reframing Magna Carta – Comprehensive Planning and Pragmatic Outcomes

Abstract In preparation for the British Library’s exhibition to mark 800 years of Magna Carta, the Library’s copies of the charter, and three related documents, were reframed. There were several requirements: minimal intervention; allow re-treatability; fully show rectos and text; present the charters as documents rather than artworks. Comprehensive risk assessments and work plans determined appropriate working methods, display angles, mounting techniques and materials, taking into account the particular features of each charter, including seals, ribbons and seal bags. Frames from commercial manufacturers were considered, and a selection made on several criteria: security, accessibility, environment, aesthetics and versatility. This project has demonstrated how a sophisticated and comprehensive initial assessment allowed a relatively simple but demonstrably appropriate solution to be implemented, using well established and understood materials and methods. This provided secure and sympathetic frames for the six documents, catering for the specific requirements of each item, and also allowed versatility should requirements change in future. We worked closely with other stakeholders, and were able to argue for the best outcomes for the objects themselves, demonstrating that high profile objects do not necessarily require expensive, “high-tech” solutions. Thorough planning and preparation ensured the reframing was completed within time and under budget.