Paper Conservation: Decisions & Compromises

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Verdigris 2: Wet Chemical Treatments which are not Easy to Decide and Apply Kyujin Ahn | Andreas Hartl | Christa Hofmann | Ute Henniges | Antje Potthast University of Natural Resources and Life Sciences, Vienna, Department of Chemistry, Vienna, Austria; Austrian National Library, Conservation Department, Vienna, Austria Introduction Paper objects with copper pigments are threatened as they may exhibit an accelerated degradation of cellulose and heavy discoloration of the paper depending on the condition of the object. In some cases, the paper eventually becomes very fragile and even handling of the object becomes critical. Paper conservators and scientists have been seeking solutions in many directions – reinforcement, environmental controls, solution treatments, etc. As a part of the forMuse programme of the Austrian Ministry of Science and Research, various solution treatments of paper with verdigris were tested simulating a practical situation that conservators might face in their workshop. In the present study, various chemical treatments of a handmade rag paper containing verdigris bound in gum arabic, will be discussed in comparison to the results obtained from the same rag paper impregnated with copper. The copper impregnation represents a more homogeneous situation which can be better controlled and monitored. Methods and Materials The solutions applied to pre-aged test specimen varied from calcium bicarbonate in water to metal ion complexing agents or antioxidants in ethanol. Spraying on a suction table and brushing on the verso were mainly applied to samples with partially soluble verdigris (Type 1). Only immersion treatment was carried out for the samples that underwent oxidation and impregnation of a fixed content of copper (Type 2) prior to the treatment. After applying accelerated aging, measurements of molar mass and carbonyl group content of samples were performed by GPC (Gel Permeation Chromatography)-Fluorescence-MALLS (Multi Angle Laser Light Scattering)-RI (Refractive Index) system after selective chemical labelling of carbonyl groups. Results None of the alkaline treatments in water nor in a mixture of water and ethanol reduced cellulose degradation significantly for samples of type 1 regardless of the application methods employed. Especially 100% aqueous alkaline treatments degraded the sample much more compared to the untreated control. On the other hand, when those solutions were applied to samples of type 2 different results are obtained: Alkaline treatments with calcium bicarbonate or magnesium propylate were both effective to reduce Mw loss and formation of carbonyl groups. Benzotriazole in ethanol which has been used in the field of metal conservation worked as the most efficient inhibitor of copper-catalyzed degradation of cellulose among the applied chemical solutions, more importantly for both types of the samples although it causes significant discoloration of paper depending on its concentration. It was also found to be effective under photo-oxidative as well as under hot and humid aging conditions. A concentration of 0.5% was high enough to form a benzotriazole-Cu complex by immersion of samples of type 2 in solution while the same concentration of benzotriazole was not yet promising for sample type 1 with a spraying application method. Calcium phytate treatment followed by a deacidfication treatment did not lead to any retardation of cellulose degradation in the presence of copper ions for both types of samples unlike for paper containing iron gall inks ((Neevel 1995; Reißland 1999). Both sample types treated with tetrabutylammonium bromide, known as an antioxidant scavenging hydroxyl radicals, exhibited significant reduction of degradation compared to the untreated control. A single application of ethyl-p-hydroxybenzoate which decreased the degradation rate when it was combined with a non-aqueous deacidfication treatment (Henniges et al. 2006) did not show any beneficial effect in terms of molar mass protection of cellulose for both sample types. ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013 36
such samples, and the underpressure of the suction table needs to be optimized depending on the respective aim, either for generating a minimum migration of copper ions and washing out of degradation products or for impregnation with an active substance. Even with the rather complex set of test samples used in this study, a simple brushing application of benzotriazole or tetrabutylammonium bromide was found to be more promising to reduce copper-induced cellulose degradation. Selection of what and how to treat papers with copper pigments is highly dependent on variables that are not only connected to the paper substrate but also depending on the conditions of the pigment. Fig. 1 Molar masses of the control samples and the samples treated with Ca(HCO 3 ) 2 in mixture of water and ethanol (2:1) by various application methods after accelerated aging. Not only the selection of the chemical treatment is important, but also the application method itself should be taken into consideration depending on the conditions of the samples and the solutions. Spraying of the reagents on a suction table did lead to a large fluctuation of target characteristics, e.g. molar mass (cf. Fig. 1) and is not easy to control when a certain amount of active agent is to deposit homogeneously. Application by brushing the reactive agent on the verso was highly efficient with sample type 1 for the treatment with benzotriazole or tetrabutylammonium bromide. On the other hand, brushing on the verso was found to be not suitable for deacidfication treatments since the paper hardly changed its pH. Discussion and Conclusions As the copper impregnated samples of type 2 were treated and analyzed together, the results obtained from samples of type 1 that are close to a practical situation were better understood. The deacidfication treatment seems to be a challenge for heavily sized inhomogeneous rag papers with partially-soluble copper pigments independent on the application method. It is always accompanied by migration of copper ions that cannot be overcome with a deacidification treatment alone. Spraying the reagents on a suction table may lead to an inhomogeneous treatment for Acknowledgements We thank all project partners at University of Natural Resources and Life Sciences, Vienna, Austrian Nation Library, the conservation department of the Austrian State Archive, and the Preservation Directorate of Library of Congress. The financial support of the Austrian Ministry of Science and Research is gratefully acknowledged. Reference Henniges, U., Banik, G., Potthast, A. 2006. ‘Comparison of aqueous and non-aqueous treatments of cellulose to reduce copper-catalyzed oxidation process’. Macromol. Symp., 232:129-136. Neevel, J. 1995. ‘Phytate: a potential conservation agent for the treatment of ink corrosion caused by irongall inks’. Restaurator, 16:143-160. Reißland, B. 1999 ‘Neue Restaurierungsmethoden für Tintenfraß mit wässrigen Phytatlösungen’. In Tintenfraßschäden und ihre Behandlung, Banik, G. and Weber, H. (eds.), Stuttgart: Kohlhammer, pp. 113-220. Authors Kyujin Ahn 1 | Andreas Hartl 2 | Christa Hofmann 2 | Ute Henniges 1 | Antje Potthast 1 1 University of Natural Resources and Life Sciences, Vienna, Department of Chemistry, Muthgasse 18, 1190 Vienna, Austria kyujin.ahn@boku.ac.at 2 Austrian National Library, Conservation Department, Josefsplatz 1, 1015 Vienna, Austria, christa.hofmann@onb.ac.at ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013 37
Page 1 and 2: Paper Conservation: Decisions & Com
Page 3 and 4: Content Lieve Watteeuw Introduction
Page 5: Michael Wheeler | Nicholas Barnard
Page 8 and 9: New Trends in Preservation in the D
Page 10 and 11: and monitoring against adverse envi
Page 12 and 13: Steve Hobaica, Patrick Loughney, Ma
Page 14 and 15: The Albums of Duke Charles de Croÿ
Page 16 and 17: Fig. 4: turning the supporting pape
Page 18 and 19: Fig. 2: Close-up of some of the los
Page 20 and 21: manuscript paper, the binding would
Page 22 and 23: Figure 2 partial sewing: the blue d
Page 24 and 25: Books in Exhibitions: History and A
Page 26 and 27: Fig. 4 Museum in London and the pre
Page 28 and 29: Risk and Safety of Illuminated Manu
Page 30 and 31: Fig. 2 Atlas, the Crown papers are
Page 32 and 33: Acknowledgments The authors would l
Page 34 and 35: Verdigris I: Compromises in Conserv
Page 38 and 39: Integrated Modelling: The Demograph
Page 40 and 41: Fig. 3: The consequence of 50 insta
Page 42 and 43: Characterisation of Historical Pape
Page 44 and 45: pling is required, tide-lines are c
Page 46 and 47: Study of Phytate Chelating Treatmen
Page 48 and 49: Evaluation of stochiometric effects
Page 50 and 51: Practice and Progress in the Conser
Page 52 and 53: Fig. 1 Fig. 2 plex picture and prov
Page 54 and 55: Fig. 2: Coloured paper strips place
Page 56 and 57: the fire (on the other hand paper,
Page 58 and 59: inform decisions on conservation tr
Page 60 and 61: This paper summarizes what is known
Page 62 and 63: 2. Methods An interdisciplinary met
Page 64 and 65: Fig. 4: Dyed endpaper pasted at the
Page 66 and 67: Preservation of Architectural Drawi
Page 68 and 69: Notes 1 According Salvador Muñoz V
Page 70 and 71: course of time under the influence
Page 72 and 73: the curators in review of the treat
Page 74 and 75: cellulose powders with cellulose et
Page 76 and 77: Authors Xing Kung Liao Conservator
Page 78 and 79: Fig. 2: Our Railroad Workers and th
Page 80 and 81: The Restoration of Cartoons at the
Page 82 and 83: tation presumes that the works are
Page 84 and 85: To Remove or Retain? - Extensive In
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Fig. 4 repeated applications until
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The Migration of Hydroxy Propyl Cel
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tion issue allowed a visualisation
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Ethical Considerations Concerning t
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emoved with damp cotton swab. Then
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Conservation of a Book of Hours fro
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Fig. 4: Pigments movement and conse
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Notes 1 Brazilwood lake, lapis lazu
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pages, which would easily have torn
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The Microflora Inhabiting Leonardo
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Acknowledgments The authors would l
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Microorganisms in Books - First Res
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hyaline white mycelia on and in the
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Deconstructing the Reconstruction E
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Fig. 3: Poster after 2012 conservat
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Conservators’ Investigation of Ch
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had been used, may be false-positiv
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function will provide a holistic pi
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Fig. 2: Patriarchs of Chan Buddhism
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ing techniques, which build upon fu
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Applications of Image Processing So
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Fig. 3 Fig. 4 images in a single wi
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Analysing Deterioration Artifacts i
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Fig. 3 similarity maps. Similarity
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Strategy in the Case of a Wrecked P
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without preliminary consolidation.
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Fiber Optic Reflectance Spectroscop
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Fig. 3: 18 th century paper seal, i
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Fig. 3 Fig. 4 of responsibilities r
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Characterising the Origin of Carbon
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Fig. 3: Sampling depth for ATR spec
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Fig. 2: Filmoplast® tape attached
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Pluchart, F. 1971. Pop Art Et Cie.
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Fig. 3: The reverse of left screen
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