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A Million Brown Spots

A Million Brown Spots






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    A Million Brown Spots A Million Brown Spots Document Transcript

    • A MILLION BROWN SPOTS AFTER CONSERVATION: UNTANGLING THE CAUSE-EFFECT CHAIN Marieke Kraan Frank J. Ligterink Birgit Reissland Bernadette van Beek Bas van Velzen Ineke Joosten Peter Hallebeek This article is published on the ICN website with permission of ICON. Edinburgh Conference Papers 2006, ed. S. Jaques (London: The Institute of Conservation, 2007), 59-66 ©2007 Institute of Conservation
    • 59 A million brown spots after conservation: untangling the cause-effect chain Marieke Kraan, Frank J. Ligterink*, Birgit Reissland, Bernadette van Beek, Bas van Velzen, Ineke Joosten and Peter Hallebeek Introduction In 2003, discolouration of a large-format contemporary artwork on paper was treated locally with hydrogen peroxide in a private paper conservation studio in The Netherlands.1 The treatment result was considered to be satisfactory. Unexpectedly, three months later, a huge number of tiny brown spots emerged in the paper (Fig 1). These spots were rather disturbing and the artwork was considered to be a total loss. During and shortly after the treatment, there had been no indications that such a problematic side-effect would arise. The choice of hydrogen peroxide as a bleaching agent and the application method used had been based on sound results obtained throughout many years‘ experience of this treatment strategy. Due to the fact that treatment with hydrogen peroxide is common in paper conservation, an explanation for the phenomenon was considered essential to anticipate and prevent similar problems in the future. Moreover, clarification of the degradation mechanism was required in order to establish a potential method for the removal of the spots. History of the artwork The artist had created the artwork in 1992, on the request of an art gallery in Fig 1 Detail of the artwork showing the different Amsterdam, using acrylic paint on paper. The paper support is white and is areas of discoloration that appeared after about 0.4mm thick. Interestingly, the paper had been bought by the owner of the hydrogen peroxide treatment. art gallery, in all probability at Peter van Ginkel Art Supplies in Amsterdam. The dimension of the artwork is large, 149.5 246.0cm. Paper of this size is only Fig 2 Detail of the artwork showing cockling in available in a rolled format. The owner received a certificate from the gallery the margin area. claiming that the work of art is a painting in acrylic paint on Fabriano™ paper. Around the central painted area the artist left all the margins unpainted, their width varying from 5cm to 20cm. The object had been hanging in the living room of the owner for a period of about ten years. It had been mounted in a wooden frame, partly covering the outer edges of the paper. After some years, the paper had started to cockle (Fig 2) and it was for this reason that the owner had contacted a conservation workshop. When the work of art was unframed it became evident that the cockling had been caused by the framing technique. The paper had been fixed onto Meranti plywood with metal staples and a white, paper-based gummed tape (Fig 3). The staples had punctured the paper all along the edges. Those edges that had been covered with the wooden frame remained white, while the unpainted paper areas, which had been exposed to daylight, displayed perceptible and relatively even discolouration (Fig 4). The conservators suggested that the paper gum-tape be removed, all the staple holes be repaired and the cockling be reduced. In response to an additional request by the owner, it was decided to reduce the local discolouration along the edges so that the artwork could be mounted in a new frame, which would allow the entire sheet to be visible after conservation. The conservation treatment was carried out in early 2003. On the recto all 1 The owner of the artwork requested that the unpainted paper areas were dry-cleaned with an eraser powder. The white paper authors not reveal the name of the artist nor support of the gummed tape adhered to the edges of the work was removed mention the title of the artwork in publications, mechanically after the local application of a 2% methyl cellulose gel to moisten nor to contact the artist nor the art gallery where the work of art was sold. Thus, all illustrations the tape adhesive. Remaining adhesive residues were removed with cotton show only details of the artwork. swabs and demineralised water. The large central area of the artwork which was Edinburgh Conference Papers 2006
    • 60 Kraan, Ligterink, Reissland, van Beek, van Velzen, Joosten and Hallebeek staple paper tape covered with thick layers of acrylic paint precluded an immersion treatment. Moreover, in view of the large size of the object, it was decided to treat the artwork meranti plywood discolouration locally. glass First, all discoloured areas were wetted from the recto with demineralised water using an airbrush. The painted areas remained untreated and were fully frame covered with blotting paper throughout the treatment. In some areas the Fig 3 Cross section diagram of the original coverage extended into some unpainted areas due to the irregular outline of the frame and mount. paint. The moisture was subsequently blotted off, with the aim of extracting water soluble coloured degradation products. This initial washing procedure was not successful, as the discolouration did not disappear. As a consequence, the treatment was extended by applying a diluted solution of, an oxidizing bleach, hydrogen peroxide in water (3%) to minimise the discolouration.2 The 1 2 hydrogen peroxide solution was applied locally with an airbrush on the discoloured areas (Fig 5 (1)). The use of an airbrush achieved a subtle continuous 3 transition between discoloured and non-discoloured areas. After the hydrogen 4 peroxide treatment the object was left to air dry overnight. The next morning the discolouration had lessened but not sufficiently. 5 Therefore, it was decided to repeat the hydrogen peroxide treatment. Directly after the airbrush application, while the object was still moist, hydrogen peroxide was locally brushed along the most discoloured areas to increase the bleaching Fig 4 Schematic drawing of a detail of the artwork before conservation, illustrating the (1) effect (Fig 5 (2)). The applied quantity of applied solution might have varied painted area (2) unpainted area (3) discoloured locally in these areas. Again, the object was air dried. As a next step, the object area (4) area covered by frame and (5) area was sprayed several times on the recto using an airbrush with demineralised covered with paper tape. water, in an attempt to remove any remaining bleach residues from the paper. Fig 5 Schematic drawing of a detail of the Surplus liquid was removed using blotting paper. The discolouration was not artwork, illustrating the areas treated with perceivable after the treatment. The staple holes and small tears were filled from hydrogen-peroxide solution: (1) airbrush the recto with cotton linters pulp. They were supported on the verso with Kōzo application (2) brush application (3) untreated. No. 3 Japanese paper and wheat starch paste. Finally, the unpainted edges were slightly flattened by spraying the paper with demineralised water and allowing them to dry between thick blotting paper under light weight. After treatment, the artwork was mounted in a new frame by a picture framer, leaving the outer 1 edges of the artwork visible. The result was evaluated to be satisfactory. The artwork was placed in the living room of the owner. 2 3 Within a period of three months, thousands of tiny brown spots had appeared in the treated areas. The owner contacted the conservators again. Local discolouration in paper Local discolouration in paper artworks is usually considered to be disturbing, whether it is in the form of spots or more general, uneven areas, and as such is a reoccurring topic in the field of paper conservation research. In some cases, local discolouration can be attributed to specific contamination. However, it is often difficult to explain specific causes for certain discolouration patterns such 2 The solution was prepared by adding as foxing or mat burn. Until now there has been no published classification with demineralised water to a concentrated solution of reagent grade hydrogen peroxide (30% v/v; a generally accepted terminology to describe discolouration patterns in paper. 10ml:90ml). A few drops of ammonia (25% v/v) Although the occurrence of local discolouration in paper is a general issue there were applied to the solution to increase the pH to are only a few documented cases to which to refer. Some of those cases showed pH7–8. certain similarities with the type of scattered, local spots of discolouration that 3 J. Hofenk de Graaff, Onderzoek Collage evolved in the artefact of this study. Matisse Documentatiemap 75/34, Centraal 1 La Perruche et la Sirène by Henri Matisse Laboratorium, Amsterdam, 1975. Unpublished research report. A well known example, for a relatively fast progressing, inhomogeneous discolouration in paper, is the collage La Perruche et la Sirène by Henri Matisse, 4 W.G.Th. Roelofs, J. Hofenk de Graaff, C.J. Fuit and P.J. Hallebeek, Onderzoek ter onder- owned by the Stedelijk Museum in Amsterdam. The large-format paper steuning van de restauratie van Henri Matisse’s support for this collage (340 775cm) had to be replaced three times, because La Perruche et la Sirène, Documentatiemap 96/21, after a period of seven years and another period of four years, local Centraal Laboratorium, Amsterdam 1996. discolouration became apparent again and again. Despite serious research Unpublished research report. attempts no final conclusion could be drawn. None of the suggested theories 5 P. Vermeulen, ‘An Investigation into the could explain the typical semi-random patterns that occurred in the Discolouration of the Background Paper of Matisse’s La Perruche et la Sirène’, The Paper background paper.3, 4, 5 The large format of the paper, the relatively fast Conservator 21 (1997): 15–25. evolving areas of discolouration as well as their random nature showed
    • A million brown spots after conservation: untangling the cause-effect chain 61 similarities with the art work discussed here. Appearance, shape and distribution of the discolouration, however, did not correspond. 2 A nineteenth-century watercolour A second case of fast appearing paper discolouration was reported for a hydrogen peroxide treatment of a watercolour in pen and brown ink carried out in 1995.6 The paper support showed intense discoloured foxing stains before conservation, especially in the sky area, that disturbed the impression of the image. Due to the presence of fugitive watercolour, only restricted aqueous treatment was feasible. It was decided to bleach the foxing stains with an aqueous solution of hydrogen peroxide, applied locally with an airbrush. To remove soluble, discoloured products from the paper, wet blotting paper had been used. Approximately six months after completion of the treatment, intense brown paper discolouration appeared on the verso. Examination under a microscope revealed that colour accents drawn in brown ink were present on the recto exactly at those places where the discolouration occurred on the verso side. Testing with a bathophenanthroline indicator for iron(II) ions indicated that the ink contained iron ions and probably was an iron-gall ink. Hydrogen peroxide is a strong oxidizing agent that, in combination with the iron(II) ions present in the ink, had caused the undesirable catalytic oxidation of the cellulose.7 The resulting cellulose-degradation products are likely to have caused the paper discolouration over time. The hydrogen peroxide treatment, the application method using an airbrush, extraction of soluble products with wet blotting paper and the short period of time until the paper discolouration appeared, all correlated with the treatment procedure carried out on the artwork in this study. Summarising, it can be stated that the development of brown spots or discolouration in paper often remains difficult to explain, and nearly impossible to predict. Important factors that play a role in the development of these type of brown spots are the materials and processes used in: the manufacture of the paper, the creation of the art work, mounting, storage and conservation. The aim of this research was to deduce which combination of factors caused the appearance of the brown spots of discolouration in the present case. Experimental 1 Visual examination The recto and verso of the artefact were examined visually under both daylight and artificial light, as well as using a UV lamp, raking and transmitted light. Details were examined with a pocket microscope (25x and 50x) and a stereomicroscope present in the conservation laboratory. The primary support was compared to samples of all Fabriano™ papers that can currently be obtained in The Netherlands in roll format, supplied by the Dutch representative of Fabriano™ (Colart B.V., Capelle aan de IJssel). According to the representative, the current range of Fabriano™ papers coincides with those sold in the 1990s. 2 Bathophenanthroline-indicator paper for iron(II) ions The presence of iron(II) ions in the paper and the discoloured spots was determined by carrying out a non-bleeding contact test with a moistened bathophenanthroline-indicator paper.8 3 Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) Paper samples from spot areas were taken with a scalpel and a pocket microscope from the surface of the verso of the artwork. The samples were analysed with Energy Dispersive Spectroscopy (EDS, Thermo Noran 6 B. Reissland, ‘Media problems: Two Case Instruments, model: Vantage) in a JEOL 5910LV Scanning Electron Microscope Studies’, Papier Conserveerend Nederland (The (SEM) in low vacuum (30 Pa), accelerating voltage 15–20 kV. Both backscattered Hague, The Netherlands, 2001) unpublished. electron images and secondary electron images were taken. 7 M. Hey, ‘Paper Bleaching: Its simple 4 X-ray diffraction (XRD) Chemistry and Working Procedures’, The Paper Conservator 2 (1977): 10–23. In addition to the SEM/EDS analysis, some samples were investigated with the help of x-ray diffraction (GADDS micro diffractometer) to determine the 8 J.G. Neevel and B. Reissland, ‘Bathophenathroline Indicator Paper, crystalline nature of the substances present. Development of a New Test for Iron Ions’, PapierRestaurierung Mitteilungen der IADA, 6 No1 (2005): 28–36.
    • 62 Kraan, Ligterink, Reissland, van Beek, van Velzen, Joosten and Hallebeek Fig 6 Detail of the artwork showing homogeneous discolouration, spots Fig 7 Detail of the artwork showing a band of spots, verso. and tide lines, recto. Results 1 Visual examination The visual examination primarily focussed on paper discolouration patterns. A number of predominant features were distinguished (Fig 6): a homogeneous discolouration, local brown spots, tide lines and patterns appearing only under UV. The homogeneous paper discolouration that had originally been present before treatment had now re-appeared with even more intensity. In comparison to the non-discoloured paper these areas showed a reduced fluorescence under UV illumination. In addition to this, a distribution of many small, brown spots had formed. Nearly all treated areas had these spots, except for the margin areas which had been covered with gummed paper tape. When looking under Fig 8 Detail of the artwork showing absence of transmitted light, additional spots were visible underneath the paper surface, in spots in an untreated area (upper part) and the core of the paper. On the verso of the artwork the spots were concentrated in presence of spots in a treated area (lower part), a band which was about 1cm wide, parallel to the edges of the object. In some recto. locations, the band broadened to a few centimetres (Fig 7). This band coincided with the area where the hydrogen peroxide had been applied with a brush. The spots were circular, with a diameter of between 0mm and 2mm. The colour of the spots varied from faint to strong brown. Within some spots the colour distribution appeared homogeneous. Other spots showed a dark brown centre surrounded by a lighter area. The outlines of the spots varied from appearing very distinct to very diffuse. Under UV illumination the spots appeared darker against their background. On the verso of the treated area the spots were smaller, more distinctively bordered and more intensely coloured than on the recto. Another type of local discolouration consisted of slightly visible tide lines. Examination under UV illumination revealed fluorescent patterns similar to wood grain in appearance on the verso that were not visible in daylight. Apart from these areas of discolouration the following other features were noticed. In the untreated areas, no brown spots were observed with the naked eye (Fig 8). However, under a microscope (magnification 25x) a sparse distribution of minute black-coloured spots could be seen. Neither the thickness, colour nor texture of available Fabriano™ papers resembled those of the paper of the artwork. Contrary to the artwork paper, all Fabriano™ papers sold in roll format contain press marks along the roll edge. It is not possible that the artist had cut off these edge marks. None of the Fabriano™ papers examined exceeded a width of 150cm, including the two press mark edges with a width of 1.5cm each. Cutting off these Fabriano™ press-marks would have resulted in a maximum width of 147cm, the object however measures 149.5cm. Along the
    • A million brown spots after conservation: untangling the cause-effect chain 63 edges, with a width of approximately 1cm, differences in gloss was observed. 2 Bathophenanthroline-indicator paper for iron(II) ions At seven locations, four on the recto and three on the verso of treated and untreated areas, the non-bleeding iron test was conducted. All brown and black spots showed a positive reaction. 3 Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) When samples were taken for analysis, it became clear that the paper within the brown spots had severely degraded. When cut, the central parts of sampled spots fell out, leaving holes in the samples. Samples with smaller spots did not have this problem to the same extent. The backscattered image of the paper surface shows such a hole within a distribution of fibres and particles (Fig 9). EDS-analysis indicated an increased iron concentration around the edges of the holes (Fig 10). For those two samples that remained intact during sampling, local increased concentrations of iron and sulphur were determined with EDS-analysis that correlated to the brown spots of discolouration (Fig 11). Closer investigation of the core areas with the highest iron concentration revealed the presence of a central particle containing iron and sulphur with a size of approximately 10–20µm (Fig 12). One particle appeared as a single, mineral-like fragment, while the other had an amorphous conglomerate structure. The majority of particles visible in the SEM images showed a plate-like particle shape and contained magnesium and Fig 9 Backscattered electron image of a sample silica. Their particle size typically ranged between 1–10µm. of spot area with hole. 4 X-ray diffraction (XRD) One of the samples with an increased iron-sulphur concentration was analysed using x-ray diffraction. The diameter of the analysed area was ca. Fig 10 Elemental map, superimposed on a 800µm. Comparison of the diffraction data with those of the reference XRD- backscattered electron image. The edges of the database matched 3 crystalline substances: clinochlore, talc and iron sulphate. hole show a higher iron concentration (in red). Discussion Applying the results of our research to the condition of the artwork and its history allowed us to develop a better understanding of the cause-effect chain that finally lead to the unexpected outcome of the conservation treatment. 1 Paper production Our starting point was the manufacture of the primary support. Although a certificate stating that the artwork was made on paper produced by Fabriano™ (Italy) appeared to have been issued by the gallery that sold the artwork, this fact could not be confirmed. It is highly unlikely that a Fabriano™ paper was used. It remains unclear who actually produced the paper. Within the paper, three materials were identified with XRD: talc, chlinochlore and iron sulphate. The first two substances are commonly used as fillers in the paper industry.9 Talc (Mg3Si4O10(OH)2) is a mineral composed of magnesium silicate hydroxide. Its chemical inertness and its excellent white colour make it particularly suitable as a filler material for paper to improve gloss, opacity, brightness and ink retention. Clinochlore (Mg,Fe2+)5Al(Si3Al)O10(OH)8 contains iron and belongs to the chlorite group of clay minerals.10 Mineral clay materials are cheap and widely used in the paper industry. They improve brightness and gloss, and increase the opacity and the printability of paper. The plate-like particle shape of both minerals is consistent with the SEM imaging. The third substance identified is iron sulphate. Its presence 9 W.R. Willets, A.M. Brooks, W.L. Craig, G. can be understood in relation to the established presence of particles with a high Haywood, C.G. Albert, J.W. Kenney, P.W. Leppla, V.A. Belcher, R.S. McClellan and F.H. Denham, iron and sulphur concentration in the paper of the artwork. Chlinochlore naturally Tappi, Paper Loading Materials, Tappi Monograph occurs together with magnetite (Fe2+ Fe3+2 O4), pyrite (FeS) and other iron Series No. 19 (New York: Technical Association sulphides. Although materials destined for use as a filler in papermaking need to of the Pulp and Paper Industry, 1958) 69. be free from contamination and require the removal of impurities, this rule appears 10 The name chlorite is derived from the Greek not to have been applied and a contaminated material was used. Iron sulphides are word chloros, meaning ‘green’, in reference to its chemically unstable substances when exposed to oxidizing environments. Under colour, not to chlorine as a compound. In literature on fillers, the minerals from the chlorite the influence of water and oxygen they are transformed in complex reaction group are often referred to as being ‘chlorite’ systems to iron(II) sulphate and sulphuric acid,11 a particularly detrimental with no further specification. combination to organic materials such as cellulose. It is probable that the paper 11 C.A.J. Appelo and D. Postma, Geochemistry, originally contained a uniform distribution of minute, to the naked eye invisible, Groundwater and Pollution, 2nd edition (Leiden: iron sulphide particles which were transformed into iron sulphate. A.A. Balkema Publishers, 2005).
    • 64 Kraan, Ligterink, Reissland, van Beek, van Velzen, Joosten and Hallebeek 2 Mounting The presence of fluorescing wood-grain-like patterns on the recto of the paper and the observed gloss along the edges were consistent with the information on the mounting technique. 3 Storage The homogeneous discolouration appeared during the time that the object was exhibited in the owners’ home. Whilst framed, different parts of the artwork had been exposed to different levels of light as some areas had been covered by either the frame or paint layers. Those areas of the paper that had had less light exposure showed a higher level of fluorescence on the verso. It is likely that an optical brightener present in the paper had degraded under the influence of UV and light in the exposed areas, causing the paper to appear more yellow. It is also likely that the temperature and humidity conditions to which the paper had been exposed varied locally in the frame. Which factor finally caused the discolouration cannot, however, be determined. 4 Conservation It is apparent that the hydrogen peroxide treatment triggered the occurrence Fig 11 Elemental map, superimposed on a backscattered electron image of a sample taken of the brown spots. Most likely the introduction of an oxidizing agent led to the from a brown spot. At the centre and left side local transformation of the iron sulphide particles to iron(II) sulphate throughout below, the iron concentrations are highest (iron the treated areas. The brush application of an additional treatment solution had in red). caused the spots to appear on the verso also. The applied blotting procedure, Fig 12 Backscattered electron image from centre intended to remove residues of the bleaching agent, has proven to be insufficient. of Fig 11. Within the high iron concentration a particle could be observed containing the Conclusions elements iron, sulphur and oxygen. The occurrence of the disturbing brown spots in the artwork can be understood as being the result of a combination of mainly two factors. The paper used for the artwork is of poor quality. In combination with the use of an oxidizing treatment agent and the, probably, insufficient washing procedure, large amounts of microscopic particles of iron sulphide, present in the paper, transformed into iron sulphate, a detrimental substance for organic materials. However, in the presence of atmospheric oxygen these iron sulphides are chemically unstable, and can have been expected, in the long run to have caused discolouration even without the addition of any treatment agent. Recommendations in paper conservation literature concerning the use of hydrogen peroxide as a bleaching agent are ambiguous. Although various authors claim that hydrogen peroxide is a relatively mild and well controllable bleaching agent, it is also known that hydrogen peroxide in combination with traces of iron and other transition metals can cause problems. Until recently however, no suitable test method has been available to conservators to test for the presence of iron. Even so, in the current case with iron-containing particles embedded in the paper, one has to doubt if their presence could have been detected beforehand. For future treatments we strongly recommend pre-testing objects for the presence of metal contamination, using a microscope, UV illumination and specific indicator tests. The occurrence of undesired side-effects as a result of a conservation treatment is rather frustrating for all parties involved. It should be stressed that risk can never be fully eliminated from the conservation profession. It is the task of conservators and conservation scientists to identify and mitigate significant risks by sharing knowledge and experience amongst themselves, and also to 12 The discolourations were removed using the following procedure: Initial thorough blotter communicate these risks in any decision making processes with owners and washing (distilled water, application from recto curators. and verso with airbrush), subsequent application of sodium borohydride in concentrations of Epilogue 0.1%, 0.4 % and 0.2% (dissolved in water with the addition of ethanol to improve the penetration), Following this research the artwork received another conservation treatment. followed by thorough blotter washing (distilled The spots have been removed.12 The object has returned to its original location in water) and a deacidification treatment applying the owners’ house. Although the current result is felt to be acceptable it is a saturated solution of calcium bicarbonate. recognized that the object remains unstable and is likely to meet more Finally, the treated areas were surface sized with gelatine (0.5% in water, application with generations of paper conservators on its path. airbrush).
    • A million brown spots after conservation: untangling the cause-effect chain 65 Acknowledgements ce cas sensibilisera les restaurateurs et leur permettra d’informer plus We would like to thank the following conservators, chemists and other précisément leurs clients sur les risques potentiels liés aux traitements avec specialists for their valuable contributions: Nico Lingbeek (Lingbeek du peroxyde d’hydrogène. papierrestauratie, NL), Francien van Daalen (van Daalen Papierrestauratie, NL), Gerhard Banik (Staatliche Akademie der Bildenden Künste Stuttgart, Zusammenfassung D), Andrea Pataki (Staatliche Akademie der Bildenden Künste Stuttgart, D), Ein großformatiges, zeitgenössisches Kunstwerk wurde lokal mit Michaela Ritter (Masson Pictet Boissonnas Gemälde-und Wasserstoffperoxid gebleicht, um Verfärbungen im Papier zu entfernen. Graphikrestaurierungen AG, CH), André van Oort (Haarlem, NL), Bob Drei Monate nach dieser Behandlung wurde eine Vielzahl kleiner brauner Hildering (Apeldoorn, NL), Linda Roundhill (Arts and Antiquities Flecken auf dem Werk sichtbar. Conservation, Woodinville, USA), Leslie Kruth (Stanford University Um dieses Phänomen zu verstehen und um ähnliche Probleme in der Library, USA), Lenkat & Madhari (India), John Havermans (TNO, Delft, Zukunft zu vermeiden, wurde das Werk visuell begutachtet und mit NL), Hiromi Tanimura (Japan), Niccolo Caldararo (San Francisco State Bathophenathrolin – Eisenindikatorpapier, Energiedispersiver University, USA), Sylvia Rodgers Albro (Library of Congress, USA), Han Röntgenspektroskopie (EDS, Thermo Noran) in einem Rasterelektronen- Neevel (ICN Amsterdam, NL). mikroskop (SEM, JEOL 5910LV) sowie mit Röntgendiffraktion (XRD, Furthermore, we would like to thank Piet van Nassau (Colart B.V., NL) GADDS Mikrodiffraktometer) analysiert. Die Untersuchungen zeigten, daß and the colleagues of Van Ginkel Kunstenaarsbenodigdheden (NL) for das Papier mit mikroskopisch kleinen Partikeln (< 10 Mikrometer) sharing information on the subject of the Fabriano™ papers as well as for kontaminiert war, die Eisen und Schwefel enthielten. Ursprung dieser the contribution of paper samples for further analysis. Verunreinigung war höchstwahrscheinlich der Ton ‘Clinochlore‘, der als Füllstoff bei der Papierproduktion eingesetzt worden war. Das Summary unglückliche Zusammenspiel der Anwesenheit der Füllstoffpartikel und A large-format contemporary artwork was locally treated with hydrogen der Wasserstoffperoxid – Behandlung verursachte ungewollt die peroxide to remove paper discoloration. Three months after treatment a katalytische Oxidation der Zellulose, was letztendlich zur Bildung der large number of small brown spots appeared in the artwork. braunen Verfärbungen in den behandelten Bereichen führte. In order to understand the phenomenon and prevent similar problems in Eine wichtige Schlussfolgerung besteht darin, daß die Restauratoren das the future, the artwork was examined visually and analysed with Problem mit den ihnen derzeit zur Verfügung stehenden Testmethoden bathophenanthroline iron-indicator paper, with energy dispersive nicht vorhersehen konnten. Wir hoffen, daß dieser Fall Restauratoren spectroscopy (EDS, Thermo Noran) in a JEOL 5910LV Scanning Electron alarmiert und es ihnen ermöglicht, ihre Auftraggeber in Zukunft Microscope (SEM) and x-ray diffraction analysis (XRD, GADDS micro umfassender über die potentiellen Risiken einer Wasserstoffperoxid – diffractometer). The research showed that the paper support was Behandlung zu informieren. contaminated with microscopically small particles (~10 micrometers) containing iron and sulphur. The source of this impurity was most likely the Resumen clay clinochlore that was introduced as filler during paper production. The Una obra contemporánea de gran formato fue localmente tratada con unlucky combination of the presence of these particles and the hydrogen peróxido de hidrógeno para eliminar descoloración en el papel. Tres meses peroxide treatment caused an undesired catalytic oxidation of the cellulose después del tratamiento aparecieron sobre la obra numerosas manchitas that finally resulted in the formation of the brown spots of discolouration in marrones. the treated area in such a short period. Con el fín de entender el fenómeno y de preveer similares problemas en It is concluded that the problem could not have been anticipated using el futuro, la obra fue visualmente examinada y analizada con papel test methods currently available to paper conservators. We hope that the indicador del hierro con fenantroline, con espectroscopía de energía present case will raise the awareness amongst conservators and will enable dispersa (EDS, Thermo Noran) en un JEOL 5910LV microscopía electrónica them to inform their clients more precisely about the potential risks de barrido (SEM) y bajo análisis de difracción por rayos X (XRD, GADDS associated with hydrogen peroxide treatments. micro difractómetro). La investigación mostró que el papel de soporte estaba contaminado con partículas microscópicas (~10 micrones) que Résumé contenían hierro y sulfuro. El orígen de estas impurezas era, muy Une oeuvre d’art contemporain de grand format a été traitée localement probablemente, la cal de clinocloro que fue introducida como relleno avec du peroxyde d’hydrogène afin d’enlever le jaunissement du papier. durante la producción del papel. La desafortunada combinación de estas Trois mois après le traitement, un grand nombre de taches brunes sont partículas y el tratamiento de peróxido de hidrógeno causó una indeseable apparues dans l’œuvre. oxidación catalítica de la celulosa que finalmente provocó, en tan corto Afin de comprendre le phénomène et pour éviter des problèmes tiempo, la formación de las descoloridas manchas marrones en el área similaires à l’avenir, l’œuvre d’art a été examinée visuellement et analysée tratada. avec un papier indicateur de la présence de fer à base de Se concluyó que el problema no podría haber sido prevenido con los bathophénanthroline, par spectroscopie à dispersion en énergie (EDS, habituales métodos de testar papel usados por los conservadores de papel. Thermo Noran) dans un microscope électronique à balayage (SEM) JEOL Esperamos que el presente caso alerte a los conservadores y que les permita 5910LV et par diffractométrie de rayons x (XRD, micro diffractomètre informar con precisión a sus clientes sobre los potenciales riesgos asociados GADDS). La recherche a montré que le support en papier était contaminé a los tratamientos de peróxido de hidrógeno. avec des particules microscopiques (~10 micromètres) contenant du fer et du soufre Il est plus que probable que la source de ces impuretés est le Biographies clinochlore de l’argile ajouté pendant la fabrication du papier comme Marieke Kraan and Bernadette van Beek jointly run the private paper charge. La combinaison malencontreuse des ces particules et le traitement conservation studio Atelier KOP in Arnhem. avec le peroxyde d’hydrogène a causé une oxydation catalytique non désirée et a finalement entraîné la formation de taches de couleur brune Frank Ligterink, Birgit Reissland, Dr. Ineke Joosten, Peter Hallebeek are dans la zone traitée dans un délai aussi court. conservation scientists at the Research Department of the Netherlands On a conclu que ce problème n’était pas prévisible par les tests Institute for Cultural Heritage (ICN). Bas van Velzen is head of the Book habituellement utilisés par les restaurateurs de papier. Nous espérons que and Paper Conservation Training Program at the ICN.
    • 66 Kraan, Ligterink, Reissland, van Beek, van Velzen, Joosten and Hallebeek Materials and suppliers Ethanol Alcohol ketonatus 96% v/v (ketonated Methyl cellulose, Methylcellulosum, 4000 m.Pa.s: Ammonia: 25%, chemical pure: ethyl alcohol): OPG Farma Interchema Fagron Farmaceuticals BV Bufa BV Rozenburg Nieuwekerk aan de IJssel Uitgeest The Netherlands The Netherlands The Netherlands Demineralized water: Gelatine powder: Sodium borohydride, powder, 98+%, nitrogen Tendo’s Genfarma BC flushed: Tenden BV Sterrebaan 14 Acros Organics Rotterdam 3606 EB Maarssen http://www.acros.com The Netherlands The Netherlands Wheat starch powder, Tritici amylum: Eraser Powder: Akablast; Cotton linters, white; Hydrogen peroxide 30%, medical pure, Genfarma BV Filter paper thin (120g m-2) and thick (300g m-2): stabilized: Zaandam Jansen Wijsmuller & Beuns Merck KGaA The Netherlands Wormer Frankfurter Strasse 250 The Netherlands 64293 Darmstadt Germany Japanese paper: Kōzo No. 3: Private supplier, Japan Contact addresses Marieke Kraan and Bernadette van Beek: Atelier KOP (Kunst Op Papier) Postbus 1221 NL-6801 BE Arnhem The Netherlands Frank Ligterink, Birgit Reissland, Dr. Ineke Joosten, Peter Hallebeek and Bas van Velzen: Netherlands Institute for Cultural Heritage (ICN) Conservation Science Department Research/Training and Education Gabriël Metsustraat 8 NL-1071 EA Amsterdam The Netherlands email: frank.ligterink@icn.nl *author to whom correspondence should be addressed