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ABSTRACT
Observations of medieval bindings revealed a distinctive material: a fine white tawed skin, similar in appearance to parchment, but with flexibility suggestive of leather. A few rare medieval recipes describe leather manufactured from parchment. The result displays properties of both materials: firmness and flexibility, thinness and high resistance, with various applications. The cover material of the observed books may derive from such a preparation. Obtaining its equivalent could be advantageous for conservation, as Christopher Clarkson already noted. This study focuses on manufacturing ‘tawed parchment', based on medieval recipes and Clarkson's experiments, whilst attempting to better understand the technique through reproduction. It is, of course, an adaptation, using modern materials. Nevertheless, the principle remains: separate collagen fibres ‘welded’ during preparation of parchment; regain a three-dimensional structure; then tan it with alum in a process analogous to tawing. Results obtained, even if they could be improved, already offer interesting conservation solutions.
ZUSAMMENFASSUNG
Manche mittelalterlichen Einbände zeigen die Verwendung eines charakteristischen Materials: eine feine, weiße alaunbehandelte Haut mit pergamentähnlichem Aussehen, jedoch mit einer Schmiegsamkeit, die eher auf Leder schließen lässt. Es existieren einige wenige mittelalterliche Rezepte, welche die Herstellung von Leder aus Pergament beschreiben. Das Ergebnis war eine Art Mischmaterial mit den Eigenschaften von sowohl Pergament als auch Leder, d. h. mit jener Festigkeit und Flexibilität sowie Dünne und hoher Beständigkeit, die für verschiedenste Anwendungen wünschenswert sind. Das Überzugsmaterial der fraglichen Bücher wurde möglicherweise in der beschriebenen Art hergestellt. Christopher Clarkson merkte bereits an, dass ein entsprechendes Material bei der Restaurierung mancher Einbände vorteilhaft sein kann. Die Herstellung von “gegerbtem Pergament” nach mittelalterlichen Rezepten und Clarksons früheren Versuchen steht im Zentrum dieser Untersuchung. Das Erzeugnis ist natürlich als Annäherung zu verstehen, unter Verwendung heute erhältlicher Materialien. Gleichwohl bleibt das Prinzip identisch: Um Kollagenfasern voneinander zu trennen, die während der Pergamentherstellung miteinander “verschweißt“ wurden, und um eine gewisse dreidimensionale Struktur zurückzugewinnen, werden sie mit einer Alaunmischung in einem dem Gerben vergleichbaren Verfahren behandelt. Es konnten gute Resultate erzielt werden und selbst wenn diese noch weiter zu verbessern wären, sind bereits interessante Restaurierungslösungen entstanden, die dieser Artikel vorstellt.
Acknowledgements
In memory of Christopher Clarkson.
Grateful thanks to Marco Di Bella, John Gillis, Leandro Gottsher, Patrice Hebrard, Andrew Honey, Flavio Marzo, Nicholas Pickwoad, Alessandro Sidoti, Stefania Signorello, Jiří Vnouček, for responding to our enquiries. Thanks also to Ciarán Ó Fearail for proofreading.
Notes
1 A UNESCO, Memory of the World Register site (UNESCO, Citation2009).
2 Accessible using the Clairvaux Virtual Library (Médiathèque Du Grand Troyes, Citation2017).
3 With the support of Biblissima (Citation2020).
4 Bernard was originally a monk of Cîteaux.
5 Literally: “bookbinders”.
6 We are using “leather” as a generic name for tanned/tawed skins, but it should be borne in mind that, “because of the variable effects of the alum process and the unusual character of the product, tanners have always given it a special name, ‘tawing’, to distinguish it from tannages which provide leather of high resistance to water, and with quite different technical properties” (Reed, Citation1972: 64).
7 Analysis carried out by Elsa Van-Eslande, Laboratoire d'Archéologie Moléculaire et Structurale, UMR-CNRS 8220, Université Pierre et Marie Curie, Paris.
8 Chamois leather, split skin, etc.
9 It would not be the same if the skin had received a tanning treatment into the leather before stretching: there would be no displacement of the fibres that are fixed by the tannin. But, according to Reed (Citation1975), if the skin has been tanned slightly, the fibre network can be stretched and in drying leads to a parchment-like structure.
10 “Take the parchment and soak it in water for 3 natural days, then take it out and let it half dry, and do not stretch it at all. Then soak it in a pan of warm water, with a handful of bran in it, mix all well together, and let the mixture stand for 2 days; then take it out and wash it in 2 or 6 waters, or until it is washed enough, and squeeze it well. Then, take a vase, and fill it more than half full with water, and add to it as much alum as you think necessary, according to the quantity you wish to make, and one or two eggs beaten up; and do it all in order: first putting the water in a pipkin, and heating it over the fire. Then adding the alum, and when the alum is dissolved let it cool until it is tepid, and then put it into a clean shell, adding to it a little wheat flour and an egg or two, and mix the alum-water well with the other ingredients; then put the said parchment into it, and stir it well in the liquor. Then let it remain for 3 days, and let the said parchment be well covered with the preparation, and keep it free from dust or other dirt. Then take out the parchment and squeeze it well, and repeat the process; then put it to dry in the shade, but do not stretch it at all, and then beat it with the hammer, and it is done” (Merrifield, Citation1849: 574).
11 Note that in the Italian the term camoscio (chamois in English) is used, instead of tawing.
12 “After being hung or piled over a wooden horse, the skins are dried in air (crusted) and held in this stage for some weeks, to allow stabilization of ‘ageing’ effect to develop. After being conditioned to a certain water content by placing in a heap of damp sawdust, the skins are staked (mechanically stretched by pulling and pressing over a fairly blunt knife blade) to obtain a soft flexible handle. What is remarkable is that by this simple procedure a product of soft handle, velvety texture and light-fast, snow-whiteness result in technical characteristics which intrigue the tanner since they are difficult to achieve by other means” (Reed, Citation1972: 63).
13 Bran was first tried, as described in medieval recipes. The pH dropped, but only to an insignificant extent.
14 Potassium double sulphate of aluminium.
15 Aubry experimented with the mechanical strength of vegetable tanned leathers. Before ageing, a leather whose thickness is reduced by 30% loses 50 to 70% of its tensile strength. Reduced by 50%, this loss is 80 to 90% (Aubry, Citation2002: 124–125).
Additional information
Notes on contributors
Cédric Lelièvre
Cédric Lelièvre is a freelance book conservator based in Nîmes (south of France). He started his career in 2001 and has run his own business since 2006. He mostly treats early manuscripts and printed books from public collections but also undertakes commissions for preventive conservation evaluations and provides advice to museums, archives and libraries. During the last several years a number of important libraries, including those of Orléans, Carpentras and Troyes, have entrusted to him the conservation of some unique medieval manuscripts and bindings. Cédric’s passion for the construction and mechanism of books started thanks to Christopher Clarkson and Nicholas Pickwoad, whom he studied under in Spoleto (Italy). He was a member of the Ligatus team at St Catherine’s monastery (Egypt) on two occasions, which allowed him to more intensely study and observe early bookbindings. He has just started researching archive material and, more specifically, the first ledger bindings, to try to understand their evolution. Email: [email protected]
Élodie Lévêque
Élodie Lévêque is a Senior conservator in Trinity College Dublin and a member of the Beast to Craft Project (University of Copenhagen). She previously worked at the Institut de Recherche et d’Histoire des Textes (CNRS) in Paris as a research engineer. Prior to this, Elodie was a Manuscript Conservator at Montpellier University Library. For the past 6 years, her main focus has been on medieval bindings from the Clairvaux Collection of manuscripts. She also worked for the National Library of Ireland (2010–2016), conserving the Library’s manuscripts collections, incl. the Gaelic and the Ormond Deeds Collections. She is the author of numerous publications about manuscript conservation, in international peer-reviewed scientific journals such as the Journal of Paper Conservation; in addition, she is part of the seminar advisory board for Care and Conservation of Manuscripts (University of Copenhagen). She is a member of the International Council of Museums (Committee for Conservation), and of the International Association of Book and Paper Conservators (IADA). She graduated from the Sorbonne (Paris) in 2010. IRHT/CNRS, 40 avenue d’Iena, Paris 75016, France. Glucksman Conservation Department, The Library of Trinity College Dublin, Dublin 2, Ireland, https://www.tcd.ie/library/preservation/. Email: [email protected]
Claire Chahine
A former CNRS research engineer, Claire Chahine founded the leather and parchment department of CRC (Centre de Recherche sur la Conservation) in Paris, where she conducted research on the preservation and conservation of these materials. In this field, she collaborated in several European research programmes. She is the author of ‘Leather and Parchment or the Metamorphosis of Skin’ published in 2013 by CNRS-Editions. Since her retirement, she has been participating in the work of ARSAG (www.arsag.fr) including the publication of its journal Support / Tracé, of which she is now editorial director. Email: [email protected]