Volume 16, Number 1, Jan. 1994, pp.21-22

The Conservation of Medieval Manuscript Illuminations and the Question of Compensation

Summary: The problem of flake loss and deterioration of the paint layer in medieval manuscript illumination has inspired a variety of remedies over the ages. Repainting large areas of an illumination or replacing whole miniatures was an accepted practice used by medieval illuminators as well as nineteenth- century restorers to compensate for losses in medieval manuscripts. Today the conservator's responsibility is twofold: to arrest causes for further flake loss, and to stabilize the condition of the design. Of course, the least invasive approach would be to reduce or eliminate any handling of the manuscript, but that may not be a practical solution. The dilemma, then, is whether to introduce a potentially non-reversible consolidant to stabilize the paint layer or to allow active flaking to continue.

Consolidants Used in Manuscript Conservation

In choosing a consolidant, all aspects of its appropriateness must be considered, such as its surface appearance, adhesive strength, working characteristics, and its effect upon the pigments, colorants, and media being treated. Unlike tempera (that is, egg emulsion) paintings, the media used in manuscript paintings and writing inks on parchment can remain water soluble after drying.

Among the many non-aqueous consolidants that have been suggested in the last ten years for flaking or friable media on parchment are: methyl methacrylate; methyl cellulose in ethanol; cellulose acetate; methyl cellulose in methylene/methanol chloride for text inks; Plexigum P-24, a synthetic resin; and in Russia, "Ftorolon" and "VA 2 EHA," a synthetic resin. Thirty years ago, microcrystalline wax, beeswax mixed with dammar resin, and soluble nylon were used to consolidate flake losses in manuscript illumination, but they are no longer used (see bibliography).

Gelatin or parchment size have been the aqueous consolidants most generally used to treat flaking pigments and inks on parchment. These consolidants have to be used sparingly so as not to dissolve medium-rich pigments, like an organic glaze or a granular paint film. On the other hand, a non-aqueous consolidant is potentially reversible, will not dissolve a water soluble medium, and is less hygroscopic but can leave a shiny, synthetic-looking residue and can overpenetrate and hence darken the skin. Caution must be used with both types of consolidant, so as not to saturate matte colors and change the reflectance, color, or surface gloss of the pigment. Furthermore, one question that has yet to be studied is whether our applying a localized consolidant might, in a microscopic way, be repeating the problem that was unforeseen by the manuscript illuminator when he or she painted a thin organic glaze over a different pigment, and which today appears as the cause of certain flake loss.

Parchment Repair and Infilling of Losses

The techniques first published by Tony Cains in his pioneering article in The Paper Conservator in 1982 are informed by his study of manufacturing methods of parchment and medieval repair techniques, such as the "baseball stitch," a mend similar to a medieval parchment maker's repair. In addition, Cains perfected a method of flattening parchment using a light tensioning method (employing padded clamps and pins into a homosote board, not weights as his predecessors had used). By tensioning the skin, the fiber bundles realign to the state the sheet was in originally when it was stretched on the frame during its manufacture. This method of flattening necessitates one to use parchment and skin materials for the infilling of losses and the repair of tears, since these repair materials must have a similar elasticity as the support.

An alternate method for infilling losses in parchment is to use toned, long-fibered Japanese paper. After realigning the design where necessary, losses are infilled using a laminate of Japanese paper and wheat starch paste; the leaves are then lightly humidified and pressed between blotters and weighted, as one would normally treat paper.

Each method has its own advantages. Although some might advocate only using skin materials to repair parchment, while others will recommend only using Japanese paper and believe that a parchment repair will introduce new stresses, both can be used to great effect. Treatment of a set of 9th c. Bible leaves in the Getty's collection (Ludwig I.1) illustrates the use of both techniques, as the leaves had been cut into sections and used in the binding of a 16th c. printed book. The first task was to humidify and realign the lines of text, using Tony Cains's tensioning method; the sections were held together with fish skin, then humidified overall, tensioned (and the process repeated) until the lines of text were realigned. The final infill, though, was made using Japanese paper, since the cut edges of the leaves made a parchment infill difficult to adhere, and the paper fibers could be more easily manipulated and required less overlap so as not to obscure the letterforms of the text.

By looking at how medieval manuscripts have been treated in the past, in the Middle Ages as well as in intervening centuries, conservators can not only better understand an object's condition, but may find by studying early restoration examples of highly sympathetic treatments or materials (such as a medieval parchment maker's sewn repair) or learn from their mistakes (as we might begin to wonder about the long term effect of our local applications of consolidants). Most importantly, we should be aware of the widest possible range of treatment options, look at the underlying principle of each one, and even question its prevailing wisdom, so that we might have a well-stocked tool kit of treatment alternatives in order to select the most appropriate method for the problem at hand.

Bibliography

Bervas, Marianne: "La Restauration de Miniatures sur Parchemin," from Sauvegarde et Conservation des Photographies Dessins, Imprimes et Manuscrits, Actes des Journess internationales d'etudes de l'Association pour la Recherches Scientific sur les Arts Graphiques (Paris: 1991).

Bykova, G.Z., A.V. Ivanova, and I.P. Mokretzova: "Conservation Methods for Miniature Paintings on Parchment: Treatment of the Paint Layer," in Conservation and Restoration of Pictorial Art. edited by Norman Brommelle and Perry Smith, (London: 1976), pp. 207-209.

Cains, Anthony: "Repair Techniques for Vellum Manuscripts," The Paper Conservator, volume 7 (1982/83), pp.15-23.

Clarkson, Christopher: "Preservation and Display of Single Parchment Leaves and Fragments," Abstracts and Preprints of the Institute of Paper Conservation Conference, Cambridge, 1980, pp. 113-119.

Clarkson, Christopher: "Rediscovering Parchment: The Nature of the Beast," The Paper Conservator, volume 16 (1992), pp.5-26.

Drayman, Terry: "The Conservation of a Petrarch Manuscript," Journal of the Walters Art Gallery, volume 30-31, (1968-1969), pp. 119-123.

Keck, Sheldon: "Mechanical Alteration of the Paint Film," Studies in Conservation, vol. 14 (1969), pp.9-30.

Marconi, Bohdan: "Some Tests on the Use of Wax for Fixing Flaking Paint on Illuminated Parchment," Studies in Conservation (1961), pp. 17-21.

Plossi, M. and P. Crisostomi: "Consolidation de la Couche Picturale des Enluminures avec Polymer Synthetiques Purs," ICOM Committe 6th Triennial Meeting: Ottawa, 1981, Preprints.

Powell, Roger: "Case History of Repair and Rebinding of an Eighth-Century Vellum Manuscript," in Philip Smith, New Directions in Bookbinding, (London: 1974), pp. 164-172.

Quandt, Abigail: "The Conservation of a 12th Century Illuminated Manuscript on Vellum," Preprints of Papers Presented at the Fourteenth Annual AIC Meeting, Chicago, Illinois, May 1986, pp. 97-113.

Quandt, Abigail, "The Documentation and Treatment of a Late 13-Century Copy of Isidore of Seville's Etymologies," The Book and Paper Group Annual, volume 10, 1991, pp. 164-195.

Wachter, Otto: "Diagnosis and Therapy in Parchment and Miniature Restoration," as published in Restaurator, vol. 5, no. 1-2, (1981-2), pp.135-150, trans. by Nancy A. Miller with a foreword by J. Franklin Mowery, ed. by Jack C. Thompson, reprinted by the Caber Press (1987).

Yusupova, M.V.: "Conservation and Restoration of Manuscripts and Bindings on Parchment," Restaurator, volume 4, (1980), pp.57-69.