Education. Section about the education activities, programmes in the Lithuanian Art Museum

Plate 19. The Januševskiai nobility’s proof document, verso before.

Plate 20. The Januševskiai nobility’s proof document, verso, after treatment.

Plate 21. The fragment of the document with seal, before conservation.

Plate 22. The fragment of the document with seal, after treatment

The Baltic Nordic Conference on Conserved and Restored Works of Art 6-9 October 1999, Taliinn, Estonia. The Conservator as Investigator. Tallinn, Conservation Centre Kanut, 2000. P. 87-90.

The paper deals with the conservation of three objects, the support of which is parchment. It presents the processes of flattening and repairing, using Gore-Tex laminate, the ultrasonic humidification chamber and the suction table. A restorer is always interested not only in the result of his work, but also in a safe and comfortable course of the work. Some causes and conditions of parchment deformation and the reasons for their treatment are described. Two ways of repairing a damaged parchment are presented. A torn and strongly deformed painting "The Landscape of Plateliai" was repaired with goldbeater's skin straps coated with sturgeon glue. The "Nobility Rights Privilege" had been damaged very much by moisture and microorganisms. It was lined with Japanese paper "Kozu" and the glue was Klucel G solution in water. The original and repair materials are glued more strongly by using a suction table and, therefore, weaker glue can be applied. Thus, the original is less changed and the process remains reversible.

Parchment, deformations, flattening, repairing, Gore-Tex laminates, humidification chamber, suction table

Parchment during its production is dried while stretched on a frame in accordance with La Lande – one night in summer and several days and nights in winter. Once dried the parchment absorbs moisture slowly. The equilibrium between the fibrils and the water is reached after a rather long dampening in an environment saturated with moisture. It depends on one collagen feature: it remains together even in a damp state. Besides that, in leather cross-links appear in the collagen molecules, which is non-specific to other collagen types. They are much less in a young animal's leather and they are partly reversible. The cross-linking increases in an old animal's leather fibrils and aged parchment, and they are not decomposed neither by weak acid solutions nor by known denaturing agents such as urea which was used in conservation. Thus, when leather gets older, it becomes denser.

The cause of leather deformations is concealed in the structure of the leather fibrils. When absorbing and giving out moisture, every fibril changes greatly in its dimensions. Fibrils in leather are located unevenly and during saturation that arrangement becomes significantly clearer – small "unpredicted" areas appear in certain, less stretched and denser places. Strongly stretched and thinner places shrink even more when leather is ageing, causing wrinkles in an earlier flat sheet.

It often happens that such sheets, saturated or even worse, saturated only in spots and not dried under tension and then stored in a dry or even warm environment, fix themselves into a new relief. Straightening in some cases can be relatively simple and smooth. Success significantly depends upon how the leather absorbs moisture. Leather must have 30% humidity. Only then can it be stretched (E.Heidemann, 1992). If parchment is made of really thick calfskin, collagen fibres in it make a dense net. While being kept in 100% RH environment, only its surface becomes damp first and less humidity penetrates inside. It is not possible to relax the fibres inside the leather, therefore it is difficult to stretch it in the desired direction in the same way the manufacturer did.

Some parchment conservators are very careful about technological innovations. They think that the parchment produced in the middle ages should be conserved in the traditional way. This point of view as a principle can be accepted; though in some cases we are inclined to apply modern methods.

In the autumn of 1998, we restored 12 documents from the manuscript department of the library of the Lithuanian Academy of Sciences. We failed to get rid of the deformations of two documents by flattening them in a frame. A copy of a 1527 act by which the land property boundaries between Sofija Korčevska Rudka's and Jonas Dolobova's possessions were established had been dampened in several places. While drying the sheet separated into several planes, the parchment became deformed along the tide lines.

We dampened the parchment through a Gore-Tex laminate and flattened it in a frame. The durations of the three flattening processes were after the first dampening two hours, after the second – four and after the third – 24 hours. After flattening we continued the drying process between needle-felts (polyester PES 450/466 Lascaux), having a board and weight on top of the leather as a press. Unfortunately, the deformations in the thick calf's skin with tightly interwoven fibres remained.

We failed to dampen this parchment in the usual way. Most often Lithuanian manuscript writers used rather thick and smoothed parchment, which we successfully dampened by applying the Gore-Tex PTFE membrane on polyester felt in the course of 1-3 hours (H.Singer, 1992). Only the thin split leather parchment moistens well in an ultrasonic humidification chamber (Lascaux HC-5). The fine mist of water molecules enters the chamber via an ultrasonic damper and one can suppose that for that reason drier, thicker and denser material in it is moistened evenly but slowly and too little. Sometimes a better damping result can be reached by having combined both these methods, i.e. to begin to moisten an object in a chamber and only later transfer it into the Gore-Tex sandwich. This way was suitable in this particular case, which is mentioned above.

We moistened the document in the chamber for three hours and then through the Gore Tex for an hour. We spread polyester fleece on a suction table, switched on the suction to150 mbars, put the parchment on to the table, covered it with Melinex and by raising the covering Melinex from time to time carefully pulled out and flattened the skin by hand. Heavy pressure pushed all the parchment planes into one level and the convex places of creases smoothed out. In an hour we covered the parchment from above with polyester felt, natural latex rubbersheeting and dried it for an hour. Later we moved it to dry under a board and weight.

This document had no deep bending marks that could make the flattening on a suction table more difficult. Besides, they rarely remain after flattening in the frame. It is important to flatten parchment keeping the flesh side upwards and the hair side downwards on the table, because the hair side of leather, even when being damped is usually less resilient.

Conservators often remain unsatisfied with the fact, that after flattening and drying parchment on a suction table, the sheet becomes too flat, even its corners bend, its middle part swells. It is not difficult to avoid this. One just should not dry the parchment totally, only for a short time, making sure that the new positions of the fibres in the material are fixed. A couple of hours or slightly more is sufficient for that and later it must be put to dry under a board.

This negative aspect can help when the conservator has to get rid of large parchment deformations and work with a large quantity of material. That was necessary when we were conserving one very deteriorated painting on parchment, "The Landscape of Plateliai".

Figure 1. "The Landscape of Plateliai", verso, before conservation

Figure 2. The framed painting "The Landscape of Plateliai", verso, after conservation

The thin parchment, 38x55 cm in size had been stretched on a simple strainer and stored under very adverse conditions. It reached us spotted, speckled with tide lines, with a cracked, flaking and crumbling paint layer. The whole left edge was separated by a 2,5 cm tear and the tear angle was increasing. As one could expect, the parchment had preserved its characteristics.

Having moistening the sheet through a Gore-Tex laminate, we joined the edges of the tear and temporarily flattened them with a self-adhesive paper strip Filmoplast P. Before that the paint layer was consolidated. It was impossible to stretch and straighten the unsteady flattened parchment in a frame; therefore the suction table was used.

Even that was not easy. Through moistening the parchment both of the edges of the tear joined well into one seam. However, the deformation, according to the tear's width, migrated – the left lower angle rose and bent. Technology saved it in this case as well. We spread the wet parchment on polyester, put it on the suction table, stretched it and fixed the picture's area with a seam along the whole parameter. After that the suction of the table was switched on to 150 mbars. Melinex was put under the lower left corner of the parchment. Later the whole parchment was pressed under the board with felts and weights. A fold is better in any case then a pressed wrinkle.

We glued the seam with goldbeater's skin stripes using sturgeon glue and once more we used Filmoplast P in order to protect the seam from moisture.

We moistened the parchment three times more and flattened it in the frame gradually returning all its parts into one plane. We succeeded in doing it only after we had removed the Filmoplast P. The parchment was moistened for the fifth time and then it was stretched on the suction table with a 100 mbar suction. After an hour it was laced under a board and weights to be pressed.

Is there something new that could be said about parchment reparation? One has read in La Lande's treatise that parchment producers repairing parchment dampened it, covered a patch with gum Arabic and flattened it with a hammer. The strength of the seam always depends on two things: the glue's strength and the force, which presses the strengthening agent to the original material. Both aspects depend upon one another.

First – the tear was repaired in the picture "The Landscape of Plateliai". It was mentioned above that this parchment was comparatively thin and it absorbed moisture very quickly. The seam, as one can understand, should be very firm. 1,5 cm wide goldbeater's skin strips were prepared in advance. They were covered with 7% sturgeon glue, dried and covered once more with 5% glue and then they were dried again. Before repairing the parchment the strips were moistened with water. Then one had to wait for the glue to swell. After that the strips were attached to the parchment where the tear was. Then we turned the seam side down towards the suction table, allowing the moisture to be absorbed directly into a polyester fleece spread under the parchment. The thin goldbeater's skin was pressed with a 100 mbars suction, glued firmly and the glue surplus was not absorbed into the original.

In another case, while conserving the Januševskiai proof of nobility document, it was essential to mechanically strengthen a great part of the parchment damaged by humidity and microorganisms. As we did not have any possibility to restore the lost part with parchment, we decided to use Japanese paper and in such way to stop the deterioration of the parchment. Other smaller tears that existed in the document were fastened with thin parchment stripes. All operations were carried out on the suction table (colour plate 19).

One worked according to a well spaceconsidered plan. Everything was prepared in advance: parchment straps were cut off and smoothed with a scalpel, Japanese paper Kozu was torn according to the contours of damages and the glue was prepared. At first the tears were fastened. For that 7% rabbit skin glue was used. The parchment stripes were covered with glue and dried. Then glued once more and put on the places of tears, then pressed with little sand bags for a short period of time. The Japanese paper was glued using a mixture of 1% Klucel G and 1,5% wheat starch "Amiel".

The parchment was put onto a polyester fleece on the suction table with the face side upwards. Japanese paper was laid under it and a 150mbar suction was switched on.

The back-side of the parchment and the whole paper were evenly sized with a prepared glue mixture using a wide brush. It was covered with woolen felt and melinex. Moisture and surplus glue were absorbed into the polyester and woolen felt, allowing the parchment and the paper to dry evenly.

For the procedure really weak glue was used. It has to be mentioned that sizing any fiber material on a suction table always gives a better result. The starch and cellulose in the glue mixture migrate to deeper layers and concentrate in areas where the fiber is the thinnest. The solution in those places is quickly absorbed and is therefore spread in large quantities. Practically, no glue layer formed between the original parchment and the Japanese paper. The repaired parts are firmly fastened to the original (A. M. Reeve, 1984) (colour plate 20).

Some conservators are skeptical about the introduction of non-original materials into parchment, but in this concrete case the lining of the document on to Japanese paper gave a good result. As this parchment part was greatly damaged by humidity and microorganisms, very thin and having separated into separate fragments, the Japanese paper was the optimum suitable choice for strengthening it mechanically. Besides, the paper saturated with liquid glue became significantly thicker and it remained elastic and not rigid. The whole document sheet became sufficiently firm and deformations did not occur immediately after the conservation or after several years (colour plates 21 and 22).

We would like to thank Nancy Bell and professor Verena Flamm, who advised on how to conserve and restore the painting on parchment and Antanas Lukšėnas, Modestas Ežerskis and Algis Blažys for the photographs taken.

1. Heidemann, E., 1991. Das Verhalten der Haut bei der Pergamentherstellung interpretiert aus der Biophysik und Biochemie ihrer Struktur.Pergament. Sigmaringen.

Die Kunsf Pergamenf zu machen. Texte und Untersuchungen zur Archivpflege 4. Munster.

3. Reeve, A.M., 1984. A New Multipurpose Low-Pressure Conservation Table for the Treatment of Paintings. Studies in Conservation vol. 29.

4. Qandt, A B., 1996. Recent Developments in the Conservation of Parchment Manuscripts. AIC, The Book and Paper Group Annual, vol. 15.

5. Singer, H., 1992. The Conservation of Parchment Objects Using Gore-Tex laminates. The Paper Conservator vol. 16.