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Pigments et colorants de l’Antiquité et du Moyen Âge

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Institut de recherche et d'histoire des textes
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Centre de recherche sur les collections
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Équipe Étude des pigments, histoire et archéologie

Session B. Mesurer, caractériser, désigner, mémoriser les couleurs

Green cooper pigments and their alteration in manuscripts or works of graphic art

Gerhard Banik

Texte intégral

Introduction

  • 1 G. BANIK, F. MAIRINGER, H. STACHELBERGER : Erscheinungen und Probleme des Kupferfrasses in der Buch (...)

1Many important historical objects in libraries and archives, mainly illuminated manuscripts, documents, coloured prints and maps show serious damage as a result of destructive effects of pigments and inks. These documents therefore are acutely endangered. Often these deterioration phenomena are caused by green copper based pigments. Only few cases are known where the blue copper pigment - azurite - causes the decomposition of paper. The degree of damage ranges from colour change in painted areas to total destruction of pigments and carrier materials, papyrus, paper and parchment. The destruction occurs in several stages. First the green colour bleeds through the sheet, this is usually followed by an intensive browning of the painted area and finally the support becomes extremely brittle. Handling of objects in this state leads to perforation and losses1 (fig. 1). Besides the destructive action of green pigments, copper alloys - usually brass - which have been used in order to imitate gilding, cause similar destruction effects to paper objects. The chemical mechanism of the destruction phenomena was not fully understood for a long time although numerous theories have been proposed to explain the decay of papyrus, paper and parchment documents. This is not astonishing, as there are many possibilities of chemical reaction between copper pigments, binding media and the paper or parchment support. The chemical mechanisms of these processes are hard to fathom. The desire to preserve these items makes the development of effective treatment methods necessary, which can only be possible after clarification of the chemical reasons for deterioration.

Fig. 1. Damage of paper caused by green copper pigments. Green illuminated areas of the paper carrier show brown discolouration and perforation. (Abraham de Bruyn, Book on Costumes, 1578, p. 57, Austrian National Library, Theatre-collection, Inv. No. 622.191-C Rara).

  • 2 A. HABERDITZL : Untersuchungen über Abbauprozesse an Pergament, PhD Thesis, Technical University Vi (...)

2The origin of the destructive mechanism of copper based pigments is the result of a complex overlapping of different processes, the natural ageing of paper as well as the composition of pigments or occasionally metallic leaves and their ability to create chemical reactions with the carrier or the medium. These processes are strongly influenced by pollution, environmental and storage conditions, especially temperature and humidity. In case of paper also sizing and inorganic fillers play an important role. It is the goal of scientific research to unravel the chemical mechanisms of degradation in order to develop conservation methods which at least manage to slow down the progress of damage. Chemical investigations, however, come up against some basic difficulties. Firstly, it must be noted that damage varies in appearance. Hardly any reliable and dated reference material exists for the interpretation and subsequent documentation of results of the analytical examinations of samples taken from damaged objects. Furthermore a knowledge of historical manufacturing processes of the objects, their individual provenance, previous conservation treatments and storage conditions are some of the numerous parameters determining cause and degree of damage. This is exactly the sort of knowledge needed by a chemist and here the greatest lacunae exist. The literature covering the subject of chemical reasons for deterioration offers little support. The information available about degradation of paper/cellulose refers to natural ageing, but does hardly cover the additional influence of transition metal ion such as copper or iron. Often the information is discordant if not contradictory. Information on the degradation of protein-based materials such as parchment through pigments or metal leaves is non-existent in the literature with the exception of systematic investigations in this field recently undertaken by Haberditzl2.

Pigments

  • 3 J.G. GENTELE : Lehrbuch der Farbenfabrikation, F. Vieweg & Sohn, Braunschweig 1906.
  • 4 G. PLESSOW : Die Anstrichstoffe, W. de Gruyter, Berlin 1928.

3Until the rise of the chemical industry in the 19th century only a few green pigments with adequate fastness, chemical stability, colouring and covering power were known. Therefore the traditional use of green pigments containing copper persisted up to the beginning of the 20th century although their destructive nature and their lack of permanence were known34.

  • 5 PLINIUS : Naturgeschichte, translated by J.D. DENSO, Röser, Rostock 1764.
  • 6 S. AUGUSTI : I Colori Pompeiani, De Luca, 1967. Roma, p. 101.

4Some of these pigments were already used in the ancient world, such as malachite, chrysocolla and basic and neutral verdigris56. Among the green copper pigment verdigris - copper acetate in different modifications - and malachite - basic copper carbonate - were the most common used green pigments for colouration of books and works of graphic art. Malachite is generally considered as a stable and harmless pigment as far as its chemical reactivity with paper and parchment as support is concerned. The destructive effect - however - is frequently ascribed to the various forms of verdigris.

5Verdigris - copper acetate - is formed as a result of the treatment of copper or copper alloys with vinegar. According to the type of vinegar used and to additives, such as urine, honey etc. which are mentioned in old recipes, a number of different copper compounds are formed which strongly differ in colour and solubility. Only little information is available on the exact chemical composition of the pigment - called verdigris - that was used for illumination during the middle ages.

  • 7 D.V. THOMPSON: The Materials of Medieval Painting, George Allen and Unwin Ltd, London 1936, p. 163- (...)
  • 8 THEOPHYLUS: On Divers Arts, translated by J.G. HAWTHORNE and C. Stanley SMITH, Dover New York, 1979 (...)

6Usually verdigris was produced by hanging plates of copper over hot vinegar in a sealed container until green crystals were formed on the copper plate. Numerous recipes exist. In all these recipes copper metal or a copper alloy, such as bronze and later brass, were made to react with vinegar in presence of oxygen with excess of carbon dioxide. The reaction took place at elevated temperature for example in a dung hill7. The resulting products were complicated mixtures of basic and neutral copper acetates with malachite and some additional phases which could not be identified up to now. An interesting point is, that there exist variations of these recipes leading to a different green copper pigment called salt green or spanish green 8. Salt green was made following a procedure similar to the production of verdigris, but in this case the copper plates were coated with honey and salt. The resulting products then were again mixtures of basic copper salts, where besides copper acetates and carbonates basic copper chlorides were formed.

  • 9 V. RADOSAVLJEVIC: Conservation of Miniatures, ICOM Committee for Conservation, 3rd Triennial Meetin (...)

7In western Europe verdigris was generally made by treating copper or its alloys with vinegar. In the Near East, in Russia and Serbia sour milk was used instead of vinegar. This procedure led to products of different colour. According to investigations of Radosavljevic9 the chemical composition of this pigment is similar to malachite.

8It is not exactly known what effect traces of other metallic elements alloyed with the copper may have upon the composition and the reactivity of the resulting pigment. In addition it should be noted, that the different additives and the different types of vinegar used for the production of verdigris lead to a combination of not only acetates, but also copper malates and tartrates. Summarizing it can be said, that modern types of verdigris differ strongly in chemical composition and reactivity from products received from medieval recipes. There are indications in the historical sources that the term verdigris was used for different products as it is mentioned that the resulting pigment sometimes was nearly insoluble in water and sometimes showed high solubility in water. It seems to be evident that solubility is a keyword for the chemical reactivity of copper compounds especially as far as organic media are concerned.

  • 10 CENNINO D’ANDREA CENNINI: The Craftman’s Handbook, translated by D.V. THOMPSON Jr., Dover, New York (...)
  • 11 THEOPHYLUS: On Divers Arts, translated by J.G. HAWTHORNE and C. Stanley SMITH, Dover New York, 1979 (...)

9Very early the poor stability of some copper pigments was known by artists. The phenomena were described in the sources for example by Cennini10 who mentioned that verdigris «... is beautiful for the eye but it does not last...», or by Theophylus11 who warned of using salt green for book illumination: «Salt green is not good for books».

Table 1.Green copper containing pigments identified in illuminated manuscripts and works of graphic art (12, 13).

Table 1.Green copper containing pigments identified in illuminated manuscripts and works of graphic art (12, 13).
  • 12 E.H. VAN’T HUL-EHRNREICH, P.B. HALLEBEEK: A New Kind of Old Green Copper Pigments Found, ICOM Commi (...)
  • 13 G. BANIK: Naturwissenschaftliche Untersuchungen zur Aufklärung des Kupferfrasses an graphischen Kun (...)

10As said before, the sources for painting techniques mention a number of recipes for manufacturing copper based green pigments. The procedures allow the formation of a number of different basic copper salts. In fact, analyses of original samples show apart from malachite and the different types of verdigris many unusual copper compounds being present in green illuminated areas. Often there is an indication, that a chemical reaction of the pigment applied as colouring matter has taken place. Copper compounds identified to be present as green colouring matters in manuscripts or works of graphic art are given in table 11213.

11Especially interesting was the fact that copper chlorides present in original samples were mostly taken from undestructed areas of objects under investigation. In the published literature copper chlorides often are mentioned as being most destructive for paper and parchment. In our investigation there is no proof of a connection between the presence of basic copper chlorides and the decomposition of the carrier materials.

Analytical procedures

  • 14 G. BANIK, J. PONAHLO: Some Aspects Concerning the Degradation Phenomena of Paper Caused by Green Co (...)
  • 15 F. MAIRINGER, G. BANIK, W. KOEHLER, H. STACHELBERGER: Halbquantitative Röntgenmikroanalyse von Pigm (...)

12Pigments from original samples were analyzed be means of X-ray diffraction (Gandolfi technique), infrared spectroscopy and scanning electron microscopy (SEM) in combination with energy dispersive X-ray micro-analysis (EDS). Using X-ray diffraction and infrared spectroscopy green pigments often could be identified without problems in case of minor decay of pigments and carrier materials14. Analyzing pigments from badly damaged objects gets exceedingly difficult as the decomposition process affects the paint layer. The small amount of pigment particles remaining on those samples are indefinable, partially amorphous products of a reaction between the copper pigment itself and the decomposition products of the cellulose. In order to get better insight into the chemical composition of the remaining green particles a special analytical procedure was developped, that allows a non-destructive sampling of single grains of pigments from a surface15. The qualitative and quantitative analysis of single pigment grains is carried out by means of energy dispersive X-ray micro-analysis (EDS) in combination with a scanning electron microscope (SEM). Sampling is done by pressing a polished resin block equipped with a fine copper grid onto the surface of the object. Doing this a sufficient number of pigment particles stick to the surface of the resin block by electrostatic adhesion forces without need for an additional adhesive. The adhesion forces are strong enough to prevent migration or dislocation of the particles during the analytical procedure. The block loaded with the sample is then viewed under the light microscope and colour slides of the interesting areas are taken. The copper grid on one hand provides a coordinate system which helps to retrieve a selected particle on the image screen of the electron microscope and on the other hand serves as an internal element standard for the quantitative analysis of the occuring copper compounds (fig. 2). The colour rendition of the particles is obtained by projecting the colour slides simultaneously for comparison. The sampling technique leaves absolutely no visible traces or destruction on the object. The procedure allows the identification of several copper pigments being present e.g. basic and neutral verdigris, malachite and a chlorine containing copper compound. The latter must be according to its elemental composition (Cu 55 %, Cl 15-16 %) one of the many existing basic copper chlorides, besides the wellknown atacamite and para-atacamite (Cu 59, 5 %, C1 16, 7 %).

Fig. 2. SEM image of a specimen positionwith selected pigment grain (arrow)(15).

13From these analytical investigations it became evident that an increasing degree of damage leads to a decrease of copper in the remaining pigment particles. In extreme cases their copper content is as low as 8-10 %, which makes it impossible to identify the type of pigment that was originally used.

Decomposition mechanisms of support materials

14The damaged paper support contains copper in the oxidation state + 1 and + 2. The formation of copper compounds with copper present in the oxidation state + 1 can only be explained by the fact that a reduction of the originally used copper compound with the oxidation state + 2, has taken place. Moreover the cellulose in paper samples from damaged painted areas is largely depolymerized. The degree of polymerization is between 60 and 80. In samples from unpainted batches the degree of polymerization is between 200 and 500. This provides sufficient strength of the paper support. The extraordinary low degree of polymerization of cellulose in damaged areas explains the lack of strength and flexibility of paper.

15It should be mentioned, that the cellulose chain is split under acid conditions at the glucosidic linkage. Under acid and even under neutral conditions the new endgroups formed are aldehydes. Under alkaline conditions the new endgroups are carboxyl groups. The amorphous irregular parts of the cellulose fibres are attacked first by hydrolysis and oxidation.

  • 16 J.S ARNEY, A.J. JAKOBS, R. NEWMAN: The Influence of Deacidification on the Deterioration of Paper, (...)

16According to investigations of Arney et al.16 it is difficult to estimate the influence of acidity and oxidation on the decomposition of cellulose. The influence of pH on oxidation of cellulose is not fully explained and depends on the type of oxidation media. Transition metal ions, such as copper are capable to catalyze oxidation of cellulose in a wide pH range and cause extensive depolymerization of the cellulose chain. It highly seems, that the mechanics and the speed of the reaction are not as much determined by pH but by the transition metal ion and its concentration in the organic matrix.

  • 17 C.J. SHAHBANI, F.H. HENGEMIHLE: The Influence of Copper and Iron on the Permanence of Paper, in: Hi (...)
  • 18 L.F. McBURNEY: Cellulose and Cellulose Derivatives, E. Ott, H.M. Spurlin, M.W. Grafflin Eds., Inter (...)

17Interaction of copper ions with cellulose occurs under acid and alkaline conditions17. An important role is played by the capacity of the cellulose to absorbe copper ions. The copper ion is easily exchanged with the proton of the carboxyl groups of oxidized or partly oxidized cellulose under suitable conditions. Copper binding by cellulose is also possible by complexation of the metal ion with hydroxyl groups18. According to recent results absorption of copper increases noticeably with formation of carboxyl groups in cellulose which are formed as a result of cellulose oxidation under alkaline conditions. In addition it should be mentioned that copper acetate - i.e. verdigris - which is to a small extent soluble in water is slightly acid in aqueous solution. Verdigris is much better absorbed by cellulose fibres than other copper pigments. The uptake of verdigris by cellulose is strongly influenced by the used vehicle, for example wine, vinegar or honey.

  • 19 K.A. JAKES, J.H. HOWARD: Replacement of Protein and Cellulosic Fibers by Copper Minerals and the Fo (...)

18Copper ions are bound in a similar way to functional groups of proteins, for example parchment. Copper is readily taken up by amino groups under appropriate pH conditions and subsequently will complex with free carboxyl groups19.

  • 20 H. STACHELBERGER, G. BANIK, A. HABERDITZL: Naturwissenschaftliche Untersuchungen zum Pergament: Met (...)
  • 21 C. DEASY: Degradation of Collagen by Metal Ion - Hydrogen-peroxide Systems IV,J. American Leather A (...)

19Collagenous materials, such as parchment, are very sensitive to the detrimental action of several metal ions. Some of these can cause decomposition reactions involving the metal ion and hydrogen peroxide. The reaction is either started by the formation of hydrogen peroxide in the collagenous material due to UV radiation or by oxidation of unsaturated fats present. Reactions of this type will cause depolymerization of a protein polymer through the breaking of the peptide bonds. This reaction takes place at room temperature and finally the material will become water soluble20. Besides other ions, copper-(II) and iron-(II) will catalyze and accelerate this reaction. Compared to other metallic contaminants copper-(II) is the most effective metal ion. The effectiveness of copper ions as oxidative catalysts for collagen was demonstrated by Deasy21 by immersion of skin collagen in aqueous solutions of copper-(II) ions and hydrogen peroxide. Even a very small copper-ion concentration of 5 x 10-4M together with 3 % H2O2 leads to total decomposition of collagen, which then becomes water soluble (fig. 3). If the copper concentration is raised to 5 x 10 2M - still a rather low concentration - only 0. 5 % H2O2 is sufficient for the same result. There is an analogy between the extensive breakdown of collagen/parchment by metal/hydrogen peroxide systems and the decay of cellulose/paper by identical reaction systems. These mechanisms play an important role in the course of the destructive action of green copper pigments.

Fig. 3. Splitting of the peptide bond by copper ions and hydrogen peroxide (21).

20Coming back to paper respectively to cellulose, and its behaviour towards green copper pigments, the following mechanisms are possible:

    • 22 W. EVANS, W.D. NICOLL, G.C. STROUSE, C.E. WARING: The Mechanism of Carbohydrate Oxidation IX. The A (...)

    In an acid environment the oxidative decomposition of carbohydrates through the action of copper acetate follows a radicalic mechanism22.

    • 23 G. BANIK, H. STACHELBERGER: Identifizierung von Abbauprodukten der Cellulose in mit Kupferpigmenten (...)

    In an alkaline environment, the oxidative decomposition of cellulose catalyzed by copper ions leads to the formation of reducing groups, which together with the copper ions present react according to the well-known Fehling-reaction. The reaction products as shown in fig. 4, were identified by means of gas-chromatography in a number of damaged samples taken from original materials23. From these results, one can assume that at least the final stage of the destruction process and the intense browning of the paper is similar to this reaction.

Fig. 4. Gas-chromatographic separationof the water-soluble products of oxidative cellulose degradation caused by green copper pigments. Sample taken from p. 115 of the book on costumes (Fig. 1).
Key: I glycolic acid, II, III not identified, IV glyceric acid, V not identified, VI erythronic acid, VII threonic acid,VIII, IX 3-desoxypentonic acids, X ribonic acid and/or arabonic acid (23).

  • 24 G. BANIK, H. STACHELBERGER : Untersuchung von Pigmentschäden am Papierträger illuminierter graphisc (...)

21A final word on the morphological appearance of the damaged fibres. Severe changes, such as fissured surfaces or fibrillations of the fibres are seldom observed. In cross sections however, extensive internal changes, mainly the formation of large central cavities, can be seen. Desintegration of the paper fibres seems to start primarily at the lumen and according to elemental analysis the fibres show a relatively high copper content of about 8 % in the interior24. It therefore can be assumed that especially absorbent and water soluble copper compounds like verdigris are leaders in causing pigment destruction and the decay of the supporting materials.

22Under special circumstances deterioration of basic copper carbonates either malachite or azurite are documented. Azurite sometimes shows transition from blue to green. This is understandable as there exists a reversible balance between blue azurite and carbon dioxide on one side and green malachite and water on the other side, which is given in the following equation.

233 Cu2 (OH)2 CO3 + CO2 (g) ⇌ 2Cu3 (OH)2 (CO3)2 +H2O (1)

  • 25 R.M. GARRELS, C.L. CHRIST : Solutions, Minerals and Equilibria, Harper and Row, New York, 1965 p. 1 (...)
  • 26 HANNAH SINGER : Ein Beitrag zur Restaurierungsproblematik von Malerei auf grundierten Papierträgerm (...)
  • 27 F. MAIRINGER, G. BANIK, H. STACHELBERGER, A. VENDL, J. PONAHLO: The Destruction of Paper by Green C (...)

24From thermodynamic considerations there is indication that malachite should be stable when the partial pressure of carbon dioxide under normal conditions is below 2. 4 mm Hg. Under a higher partial pressure of carbon dioxide azurite is formed. Since the partial pressure of carbon dioxide in air is about 0. 24 mm Hg, it is evident that under normal conditions azurite tends to loose CO2 in presence of moisture and converts into green malachite25. This effect can be observed in some illuminated manuscripts stored under humid conditions26. As the conversion-reaction goes along with an increase of solubility, a destruction of the carrier material sometimes occurs. In some cases malachite, usually regarded as a stable, non-destrutive pigment, causes decay on paper (fig. 5). It is assumed that a starting reagent for the destruction phenomena is the long term influence of sulfur-dioxide, light and humidity. By this the basic copper carbonate is at least partly converted to a more soluble, basic copper sulfate which then accelerates the decomposition of the support27.

  • 28 G. BANIK: Mikroanalytische Untersuchung von Vergoldungsmaterialien in der Buchmalerei, Mikrochimica (...)

25Imitation of gilding on the basis of copper alloys - mostly brass - can produce similar damage as it can be observed with copper pigments (fig. 6)28. This decay is a result of the corrosion of the copper alloy under the influence of sufficient moisture. In this case a soluble copper-(II) compound is formed which penetrates into the paper web causing a green discolouration under the gilding. Analysis of the corrosion products showed the presence of basic copper carbonates, but the exact composition could not be identified. Corrosion of the metal leaf is autocatalytically accelerated, if metallic copper or a copper alloy is present besides copper ions. The final stage of this type of destruction is a deep brown discolouration and embrittlement of the support. The chemical mechanism follows similar reactions as are described above to explain the destructive effects of copper pigments. Decomposition of the metal layer and the support will continue as long as there is sufficient humidity and non-corroded metal on the paper.

Conclusion

26Although our knowledge about the chemical mechanisms of the decomposition of paper caused by copper pigments is still incomplete some important conclusions can be drawn. The discolouration and the loss of mechanical properties of paper is a result of the oxidizing action of soluble copper compounds. The presence of acidity plays an important role. An acid environment accelerates the decomposition reactions. Nevertheless a deacidification alone will not stop the decay unless soluble copper compounds are removed from the object or converted to chemical inert compounds.

Fig. 5. Decomposition and browning of paper caused by malachite. Object : Chinese wallpaper from Schlosshof Castle (Lower Austria).

Fig. 6. Destruction pheneomena in anilluminated manuscript (18th century)caused by corrosion of a gilding imitation (brass 92 % Cu, 8 % Zn). Object : Cod. Mixt. 838, Fol. 9, Austrian National Library, Manuscript collection (28).

Acknowledgment

27The research project «Untersuchungen der destruktiven Wirkungen von grünen Kupferpigmenten auf Papier und Pergament sowie Entwicklung geeigneter konservatorischer Massnahmen» is being supported by the Stiftung Volkswagenwerk. Collaborating institutes are the Institut für Farbenchemie, Akademie der bildenden Künste and the Staatsbibliothek Preussischer Kulturbesitz, Berlin. The author thanks the Stiftung Volkswagenwerk for the support which made the present work possible.

Notes

1 G. BANIK, F. MAIRINGER, H. STACHELBERGER : Erscheinungen und Probleme des Kupferfrasses in der Buchmalerei, Restaurator 5, (1981-1982) 71-93.

2 A. HABERDITZL : Untersuchungen über Abbauprozesse an Pergament, PhD Thesis, Technical University Vienna 1987.

3 J.G. GENTELE : Lehrbuch der Farbenfabrikation, F. Vieweg & Sohn, Braunschweig 1906.

4 G. PLESSOW : Die Anstrichstoffe, W. de Gruyter, Berlin 1928.

5 PLINIUS : Naturgeschichte, translated by J.D. DENSO, Röser, Rostock 1764.

6 S. AUGUSTI : I Colori Pompeiani, De Luca, 1967. Roma, p. 101.

7 D.V. THOMPSON: The Materials of Medieval Painting, George Allen and Unwin Ltd, London 1936, p. 163-168.

8 THEOPHYLUS: On Divers Arts, translated by J.G. HAWTHORNE and C. Stanley SMITH, Dover New York, 1979, p. 41.

9 V. RADOSAVLJEVIC: Conservation of Miniatures, ICOM Committee for Conservation, 3rd Triennial Meeting, Madrid 1972.

10 CENNINO D’ANDREA CENNINI: The Craftman’s Handbook, translated by D.V. THOMPSON Jr., Dover, New York, 1954, p. 33.

11 THEOPHYLUS: On Divers Arts, translated by J.G. HAWTHORNE and C. Stanley SMITH, Dover New York, 1979, p. 38.

12 E.H. VAN’T HUL-EHRNREICH, P.B. HALLEBEEK: A New Kind of Old Green Copper Pigments Found, ICOM Committee for Conservation, 3rd Triennial Meeting, Madrid, 1972.

13 G. BANIK: Naturwissenschaftliche Untersuchungen zur Aufklärung des Kupferfrasses an graphischen Kunstwerken, Das Papier 36, (1982) p. 438-448.

14 G. BANIK, J. PONAHLO: Some Aspects Concerning the Degradation Phenomena of Paper Caused by Green Copper Containing Pigments, ICOM Committee for Conservation, 6th Triennial Meeting, Ottawa, Preprints, 81/14/1 (1981).

15 F. MAIRINGER, G. BANIK, W. KOEHLER, H. STACHELBERGER: Halbquantitative Röntgenmikroanalyse von Pigmentpartikeln aus Farbschichten graphischer Kunstwerke - Methoden zur zerstörungsfreien Probenahme, Beitr. elektronenmikroskop. Direktabb., Oberfl. 14, (1981) p. 91-96.

16 J.S ARNEY, A.J. JAKOBS, R. NEWMAN: The Influence of Deacidification on the Deterioration of Paper, J. AIC 19, (1980) p. 12-33.

17 C.J. SHAHBANI, F.H. HENGEMIHLE: The Influence of Copper and Iron on the Permanence of Paper, in: Historic Textile and Paper Materials - Conservation and Characterization, H.L. Needles, S.H. Zeronian Eds., Advances in Chemistry Series 212, American Chemical Society, Washington, 1986, p. 387-410.

18 L.F. McBURNEY: Cellulose and Cellulose Derivatives, E. Ott, H.M. Spurlin, M.W. Grafflin Eds., Interscience, New York, 1954, p. 99-163.

19 K.A. JAKES, J.H. HOWARD: Replacement of Protein and Cellulosic Fibers by Copper Minerals and the Formation of Textile Polymorphs, in: Historic Textile and Paper Materials - Conservation and Characterization, H.L. Needles, S.H. Zeronian Eds., Advances in Chemistry Series 212, American Chemical Society, Washington, 1986, p. 277-287.

20 H. STACHELBERGER, G. BANIK, A. HABERDITZL: Naturwissenschaftliche Untersuchungen zum Pergament: Methoden und Probleme, in press.

21 C. DEASY: Degradation of Collagen by Metal Ion - Hydrogen-peroxide Systems IV,J. American Leather Ass. 65, (1970) p. 537-546.

22 W. EVANS, W.D. NICOLL, G.C. STROUSE, C.E. WARING: The Mechanism of Carbohydrate Oxidation IX. The Action of Copper Acetate Solutions on Glucose, Fructose and Galactose, J. American Chemical Society 50, (1928), p. 2267-2285.

23 G. BANIK, H. STACHELBERGER: Identifizierung von Abbauprodukten der Cellulose in mit Kupferpigmenten illuminierten Graphiken, Monatshefte sur Chemie 113, (1982), p. 845-848.

24 G. BANIK, H. STACHELBERGER : Untersuchung von Pigmentschäden am Papierträger illuminierter graphischer Kunstwerke, Mikroscopica Acta 86, (1982), p. 69-76.

25 R.M. GARRELS, C.L. CHRIST : Solutions, Minerals and Equilibria, Harper and Row, New York, 1965 p. 155.

26 HANNAH SINGER : Ein Beitrag zur Restaurierungsproblematik von Malerei auf grundierten Papierträgermaterialien, unpublished Seminar Report, Meisterschule für Konservierung, Akademie der bildenden Künste, Wien, 1986.

27 F. MAIRINGER, G. BANIK, H. STACHELBERGER, A. VENDL, J. PONAHLO: The Destruction of Paper by Green Copper Pigments Demonstrated by a Sample of Chinese Wallpaper, in: Preprints of the Contributions of the Vienna Congress (IIC), 7. -13. Sept. 1980 «Conservation within Historic Buildings», N.S. Brommelle, G. Thomson, P. Smith Eds., London, (1980), p. 180-185.

28 G. BANIK: Mikroanalytische Untersuchung von Vergoldungsmaterialien in der Buchmalerei, Mikrochimica Acta (Wien), I, (1983), p. 23-28.

Table des illustrations

Légende Fig. 1. Damage of paper caused by green copper pigments. Green illuminated areas of the paper carrier show brown discolouration and perforation. (Abraham de Bruyn, Book on Costumes, 1578, p. 57, Austrian National Library, Theatre-collection, Inv. No. 622.191-C Rara).
URL http://books.openedition.org/editionscnrs/docannexe/image/8132/img-1.jpg
Fichier image/jpeg, 73k
Titre Table 1.Green copper containing pigments identified in illuminated manuscripts and works of graphic art (12, 13).
URL http://books.openedition.org/editionscnrs/docannexe/image/8132/img-2.jpg
Fichier image/jpeg, 29k
Légende Fig. 2. SEM image of a specimen positionwith selected pigment grain (arrow)(15).
URL http://books.openedition.org/editionscnrs/docannexe/image/8132/img-3.jpg
Fichier image/jpeg, 62k
Légende Fig. 3. Splitting of the peptide bond by copper ions and hydrogen peroxide (21).
URL http://books.openedition.org/editionscnrs/docannexe/image/8132/img-4.jpg
Fichier image/jpeg, 16k
Légende Fig. 4. Gas-chromatographic separationof the water-soluble products of oxidative cellulose degradation caused by green copper pigments. Sample taken from p. 115 of the book on costumes (Fig. 1).Key: I glycolic acid, II, III not identified, IV glyceric acid, V not identified, VI erythronic acid, VII threonic acid,VIII, IX 3-desoxypentonic acids, X ribonic acid and/or arabonic acid (23).
URL http://books.openedition.org/editionscnrs/docannexe/image/8132/img-5.jpg
Fichier image/jpeg, 11k
Légende Fig. 5. Decomposition and browning of paper caused by malachite. Object : Chinese wallpaper from Schlosshof Castle (Lower Austria).
URL http://books.openedition.org/editionscnrs/docannexe/image/8132/img-6.jpg
Fichier image/jpeg, 28k
Légende Fig. 6. Destruction pheneomena in anilluminated manuscript (18th century)caused by corrosion of a gilding imitation (brass 92 % Cu, 8 % Zn). Object : Cod. Mixt. 838, Fol. 9, Austrian National Library, Manuscript collection (28).
URL http://books.openedition.org/editionscnrs/docannexe/image/8132/img-7.jpg
Fichier image/jpeg, 95k

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