Destruction of the Binding Media of the Green Paint Layer in an Eleventh-century Greek
Manuscript
by VILENA KIREYEVA
Technological studies of medieval manuscripts often reveal such problems as diverse causes of
destruction of parchment.1-4 Apart from such common causes as light, humidity, dust and air
pollution one can name the materials used by medieval manuscript-makers themselves, for instance
ferrogallic inks or copper pigments. The destruction caused by them can sometimes perforate the
parchment.5
A Greek Gospel book, dated 1044, from the Russian State Library (the former Lenin Library, F.27O
Ia,N 15) can be described as a typical example of such destruction. The parchment under layers of
green paint in numerous ornamental initials had lost its natural dense and fibrous texture and
acquired a somewhat jelly-like appearance. In some sections the parchment was completely
destroyed, and its losses could be detected by outlines of the initials (Fig. 1-3). This phenomenon is
a result of destructive action of green pigment, as the other paint layers and the parchment
underneath them in the other sections of the folio are well preserved. Investigation of the green
paint layer revealed the presence of Cu2+, but it was impossible to define the pigment precisely, as it
was completely destroyed.
The destructive influence of copper pigments is common knowledge. But interest should also arise
while investigating such matters as the influence of copper ions on binding media - in our case on
carbohydrate materials that were detected in paint layers of the manuscript in question. It was
identified that a gum was used as a binding material. The samples were picked up from the losses of
the paint layer found in the folds of parchment leaves. The experiments were carried out using
methods for the investigation of carbohydrate binders: histochemical and microchemical methods
and thin-layer chromatography.
The results of the investigation of samples of green pigments found in losses
Fig. 1-3. Three stages of destruction of green copper pigment and parchment underneath
of the paint layer and microsamples taken from borders of outlines of perforated initials appeared to
be unusual: no polysaccharides or monosaccharides were revealed, while analysis of undestructed
green paints as well as other pig-
ments (using the same methods) indicated the presence of a gum as a binding material. That fact led
to the idea that intense destruction of hydrocarbonate binders could be caused by the action of
copper pigments. As noted above, on sections of parchment affected by decomposed pigment, only
ions of Gu2+ were revealed.
It is known from literary sources that polysaccharides and monosaccharides with free glucoside
hydroxyl group easily react with Cu2+. The result of this reaction is the breakdown of sugars to the
simplest organic acids.910 The reaction takes place at high temperature (+60°C) and humidity. The
reaction rate increases together with accumulation of acids and they hydrolyze the reaction.
Following these data, the samples of destroyed green pigments were analyzed to reveal the simplest
organic acids, using ion-exclusion chromatography. This method helps to separate the compounds
of the simplest acids and to identify them. The mechanism of separation using this method is of
combined nature.
The separation was carried out in a column filled with ion-exchange resin, and gel-filtration
appeared to be the most essential operation for separation of molecules.
The products of destruction were identified in a nonhydrolyzed specimen. It dissolved easily in
distilled water. The solution was placed in separation column using a Dionex 10 device. Separation
conditions: 6X20 mm column, Aminex as sorbent; 2 mm of benzoic acid as eluent. Eluent rate —
13 ml/min. Specimen volume - 50 microliters. In the sample of decomposed green pigment were
identified oxalic, lactic and acetic acids. So the binding material of a pigment was decomposed
under the action of ions of Cu2+ to the simplest organic acids.
In order to convince oneself that the destruction of gum owing to the action of ions of Cu2+ was not
accidental, some investigations on such action on different materials were carried on, that is on
various resins and also on honey that was often added as a plasticizer to protein binders (6-8). The
samples on parchment with paint layer on base of copper acetate Cu(CH3COO)2 were modeled.
Resins from plum, apricot and cherry trees were utilized as binders, as well as gum-arabic and
eggwhite plasticized by honey. Samples were placed in a chamber with relative humidity about
100% and temperature about 40°C. which are possible conditions for storing manuscripts in a
tropical climate. It should be noted that the increase of temperature to 60°C slowed the process of
decomposition. The destruction of resins was revealed by the method of ion-exclusion
chromatography described above. The average time needed for complete decomposition of
carbohydrate materials turned out to 160 days. It was determined that the resin from apricot tree
was decomposed to formic, oxalic and acetic acids; the resin from plum tree to oxalic, lactic and
acetic acids; the resin from cherry tree to oxalic, valeric, lactic and acetic acids; gum-arabic to
formic, oxalic and acetic acids; and honey to formic, oxalic, citric and acetic acids. Even if acetic
acid, as it may be thought, is a product of decomposition of copper acetate, the other acids
undoubtedly are the result of destruction of carbohydrate materials put on trial under the action of
ions of copper Cu2+.
Following the performed investigations, it is possible to determine that Gu2+ is active in relation to
carbohydrate binding materials in conditions of relatively high humidity and temperature not higher
than 60°C. The process of interaction in different periods of time may lead to complete destruction
of carbohydrate binder (and it should be kept in mind that its type, way of preparation and natural
qualities are important for this purpose). The results of this process may provide some additional
contribution to the destruction of the parchment as any other acid does. Traditional methods for
identification of carbohydrate binders taking into account the polysaccharides and monosaccharides in them could not be effective enough in view of the investigations described above.
SUMMARY
Destruction of the Binding Media of the Green Paint Layer in an Eleventh-century Greek
Manuscript
The investigation of the decomposed paint layer of an eleventh-century Byzantine manuscript
required a nontraditional approach to identify the carbohydrate binder. The experiments out-carried
indicated that the action of ions of Cu2+ leads not only to the destruction of parchment but also to
the decomposition of the carbohydrate binding media of the paint layer. Carbohydrate binder
decomposes to the simplest organic acids and they, in turn, contribute to the destruction of
parchment.
La destruction du liant dans la couche picturale verte d'un manuscrit grec du Xle siecle
L'etude de la couche picturale degradee d'un manuscrit byzantin du Xle siecle a necessite une
approche non traditionnelle pour identifier le liant glucidique. Les tests realises ont montre que
l'action des ions de Gu++ ne causait pas seulement la destruction du parchemin mais aussi la
decomposition du liant glucidique de la couche picturale. Le liant se decompose en acides
organiques les plus simples et ceux-ci a leur tour contribuent a la degradation du parchemin.
Zerstörung des Bindemittels in der grünen Farbe einer grkchischen Handschrift aus dem XI.
Jahrhundert
Die Untersuchung der zerstörten Farbschicht einer byzantinischen Handschrift aus dem 11. Jh.
erfor-derte eine unübliche Methode zur Erkennung von Bindemitteln auf Kohlehydratbasis. Die
Expenmente ergaben, daß zweiwertige Kupferionen nicht nur Pergament, sondern auch die
genannten Bindemittel zerstören. Die Endprodukte sind einfache organische Sauren, welche
ihrerseits zur Zerstörung des Pergaments beitragen.
REFERENCES
1. Banik, G. et al. Erschdnungen und Probteme des Kupferfrasses in der Buchmalerei. Restaurator
5 (1981-1982): 71 99.
2. Banik, G.: Matunvissenschaftliche Untersuchung zur Aufklarung des Kupferfrasses an
graphischen Kunstwerken. Das Papier 36 (1982): 43-48.
3. Banik, G. & Ponahlo, J.: Some aspects concerning the degradation phenomena of paper caused
by green copper containing pigments. ICOM Committee for Conservation, 6th Triennal Meeting,
Ottawa (1981). Preprints: 81/14/1.
4. Banik, G.: Discoloration of green copper pigments in manuscripts and works of graphic art.
Restaurator 2 (1989): 61-73.
5. Banik, G.: The influence of copper-containing pigments and iron gall inks on parchment
degradation. ICOM Committee for Conservation Working Group on Paper and Graphic
Documents. Jerusalem Meeting on Parchment. 1992, October 26th-3Oth.
6. Mokretsova, I. P.: [Materials and technique of Wtst-Emptm medieval book painting.]
Soobshtchenija VZNILKR 20 (1968): 85 (in Russian).
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the book and icon department] Pamiatniki drevney pismennosti 1 1906 in Russian .
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Vilena Kireyeva
Laboratory of Physical-Chemical Research
State Institute of Restoration
44, ul. Gastello
107014 Moscow
Russia