Authors
Charlotte GamperKaren C. ThompsonAnita Quye
Topics
Textile materials and evaluationsCultural Heritage Materials AnalysisDyeing and Modifying Textile FibersDraft 19 th March 2013 Viscose Rayon: An Absorbing Problem. An Investigation into the Impact Conservation Wet Cleaning Treatments have on Historic Woven Viscose Rayon Fabrics; with a Supplementary Analysis of Current Techniques for Identifying Man-Made Fibres.Charlotte Gamper, Karen Thompson and Anita Quye.Viscose rayon was first invented over a century ago. 1 During this time it has been known by different generic and trade names. Its relative short existence is reflected in the minimal amount of literature available on its conservation. It is likely that viscose rayon textiles will increasingly appear at the textile conservator’s workbench and therefore more research is needed, to ensure well informed treatment decisions. This project focused on the low wet strength attributed to viscose rayon textiles and aimed to explore the appropriateness of wet cleaning as a treatment option for conservators working with this fibre by conducting a series of tensile strength tests on examples of the fibre. This research was undertaken as part of the main author’s dissertation. Testing was carried out at the Centre for Textile Conservation Centre and Technical Art History (CTCTAH) at the University of Glasgow. To begin, insight into why viscose rayon fibres have the particular characteristic of poor wet strength is given, looking at manufacture and chemical composition, to explain the impetus for research. Details of testing and analysis of their results is then given, to show how this may affect conservation treatment choice. 1.1 Viscose Rayon Manufacture and its Influence on Wet Strength The viscose process, patented in 1892, was invented by British chemists Charles Cross, Clayton Beadle and Edward Bevan. 2-3 Samuel Courtauld and Co. Ltd bought the rights to the viscose process and in 1905 began textile fibre production in their factory in Coventry, England. 4 To begin, man-made fibres were developed to replicate the desirable properties of natural silk, without its high cost, named at the time artificial silks. 5 Viscose rayon today is classified as a semi-synthetic regenerated cellulosic fibre; so-called as its production involves breaking-down the cellulose polymer of wood and regenerating the cellulose polymer molecular structure in filament form. R. Moncrieff explains that: ‘[…] the final filament differs chemically from the original cellulose of the wood in only one respect – that it has suffered some degradation during the manufacturing processes: the very long cellulose molecules have been partly 1 Susannah Handley, ‘Chapter 1, 1700s-1930. The Chemist Conquers the Worm’, in Nylon: The Manmade Fashion Revolution, (London: Bloomsbury, 1999), p. 21.2 Woodings, (2001a), p. 5.3 Textile Mercury Annuals, (1953), p. 666. 4 Handley, (1999), p. 21. 5 Handley, (1999), pp. 16-17.hydrolysed and have been broken down into shorter, although still very long, molecules.’ 6This degradation imparts low wet strength to the fibre.. The first viscose rayon fibres from 1905 had especially low dry and wet strength. 7 Improvements made to manufacturing over proceeding years led to a one hundred percent increase in fibre strength by the 1920s, 8 although viscose rayon still had low wet strength compared with other fibres, as shown by a Lux washing soap advert from 1926 (Illustration. 1). Since the 1920s, progressive manufacturing modifications and the use of finishing techniques has resulted in fibres with further improved wet strength and other properties, catering for a variety of end usages. 9 In its original natural form viscose rayon has a silk-like appearance but advances in manufacturing have enabled it to be processed with appearance and handle similar to fibres like cotton and wool. 10 The most significant improvements to wet strength are documented as occurring in the 1920s, 1950s and 1970s. 11 Knowledge of manufacturing changes has revealed that older examples are likely to display poorer wet properties than later examples. It was decided to contextualise this research by assessing the extent of loss in strength for wet cleaning historical woven viscose rayon fabrics with the aim of showing whether different treatment choices, based on year of manufacture, may be appropriate. A series of controlled scientific tests were conducted on specimens of viscose rayon from three eras, c.1940s, c.1960s and c.1980/90s, dated by researching fashion/textile fashions and obtained from charity shops and online auctions for this research. Their strength was measured using a tensile strength tester. . It was hoped to obtain an earlier viscose rayon object, dated 1905-1920, as fibres produced in this period had reportedly the lowest wet strength of all, but unfortunatelyexamples could not be sourced within the project timeframe. Tensile tests aimed to show any differences between dry and wet specimens which had been subjected to a controlled wet cleaning treatment, in order to contextualise research for conservation practices. In addition, specimens were also tested which had been subjected to a controlled wet cleaning treatment and then allowed to air-dry, to show whether any changes in wet properties were permanent. It should be noted that in addition to the scope of this research, the range of manufacturing modifications, briefly mentioned above, give rise to a diversity of fibre properties available of viscose rayon which complicate predictions for fibres behaviour during wet cleaning. 6 R. W. Moncrieff, ‘Chapter 9 - Viscose Rayon’, in Man-Made Fibres, (London: Butterworth & Co Ltd, 1975), p. 164. 7 Teresa A. Summers, Billie J. Collier, John R. Collier and Janice L. Haynes, ‘History of Viscose Rayon’, in Raymond B. Seymour and Roger S. Porter (eds.) Manmade Fibers: Their Origin and Development, (Essex: Elsevier Science Publishers Ltd, 1993), p. 77. 8 John W. S. Hearle, ‘Chapter 8 – Physical Structure and Fibre Properties’, in Calvin Woodings (ed.), Regenerated Cellulosic Fibres, (Cambridge: Woodhead Publishing in association with The Textile Institute, 2001), p. 214. 9 Cook, (2009), p. 11. 10 Hatch, (1993), p. 187.11 Kathryn L. Hatch, Textile Science, (St. Paul, USA: West Publishing Company, 1993), p. 186.Therefore for conservation, it should be understood that viscose rayon may not necessarily act within a conformed XXX common format.1.2 Viscose Rayon Fibre Chemistry and its Influence on Wet Strength When regular viscose rayon fibres are wetted, they have been described as losing a significant level of strength. The textile science lecturer Kathryn Hatch explains how: ‘[Viscose] Rayon loses about 50% of its tenacity when saturated with water.’ 12 12 Hatch, (1993), p. 184.Figure 1 - Lux Soap Advert, 1926 From Photoplay Vol. 30, July 1926, (Chicago: Photoplay Magazine Publishing Company, 1926).Low degree of polymerisation, poor fibre orientation and high water absorptionare characteristics of viscose rayon resulting from its manufacturing process, and all contribute to its poor wet strength. The low degree of polymerisation and poor orientation of the cellulose II molecules of viscose rayon results in fewer hydrogen bonds in the fibres than are possible in the cellulose I of natural cellulosic fibres 13, hydrogen bonding being in part responsible for the high strength of cotton cellulose. 14 Viscose rayon’s highly amorphous polymeric structure allows easy entry of water molecules during wetting, causing a significant amount of intermolecular hydrogen bonds to be disrupted. 15 The result is a relatively much weaker fibre when wet with clear implications for wet cleaning.
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PublishedAug 1, 2012
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