Color Changes and Chemical Reactivity in Seventeenth-Century Oil Paintings © Annelies Van Loon 2008
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Color Changes and Chemical Reactivity in Seventeenth-Century Oil Paintings © Annelies van Loon 2008 All rights reserved. No parts of this publication may be transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without the prior permission in writing of the author. The work described in this thesis was performed at the FOM Institute for Atomic and Molecular Physics (AMOLF), Molecular Paintings Research Group, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands. The research is part of the De Mayerne program of the Netherlands Organization for Scientific Research (NWO) and the research program no. 49 (Mass spectrometric imaging and structural analysis of biomacromolecules) of the Foundation for Fundamental Research on Matter (FOM). ISBN/EAN 978-90-77209-17-2 Front cover Gerard van Honthorst, Frederik Hendrik’s Steadfastness, 1650-52, Oranjezaal, Royal Palace Huis ten Bosch, The Hague The Netherlands Microscope detail of whitened dark paint surface as a result of bone black degradation, see Fig. 3.B.2. Photo credit SRAL Maastricht Design & lay-out Annelies van Loon Edwin Verweij Color Changes and Chemical Reactivity in Seventeenth-Century Oil Paintings academisch proefschrift ter verkrijging van de graad van doctor aan de Universiteit van Amsterdam op gezag van de Rector Magnificus prof. dr. D.C. van den Boom ten overstaan van een door het college voor promoties ingestelde commissie, in het openbaar te verdedigen in de Agnietenkapel op dinsdag 15 januari 2008, te 12.00 uur door Annelies van Loon geboren te Alkmaar Promotiecommissie Promotor: Prof. dr. J.J. Boon Overige commissieleden: Dr. A. Burnstock Prof. dr. A.G.A. van Grevenstein-Kruse Dr. J. Kirby Atkinson Prof. dr. J.P. Filedt Kok Prof. dr. C.G. de Koster Prof. dr. P.J. Schoenmakers Faculteit der Natuurwetenschappen, Wiskunde en Informatica MOLART Reports This thesis is the fourteenth in the series of MOLART reports. The MOLART reports summarize research results obtained in the course of the MOLART and De Mayerne research programs supported by the Netherlands Organization for Scientific Research (NWO). 1. Molecular studies of fresh and aged triterpenoid varnishes, Gisela A. van der Doelen, 1999. ISBN 90-801704-3-7 2. A mathematical study on craquelure and other mechanical damage in paintings, Petri de Willigen, 1999. ISBN 90-407-1946-2 3. Solvent extractable components of oil paint films, Kenneth R. Sutherland, 2001. ISBN 90-801704-4-5 4. Molecular changes in egg tempera paint dosimeters as tools to monitor the museum environment, Oscar F. van den Brink, 2001. ISBN 90-801704-6-1 5. Discoloration in Renaissance and Baroque oil paintings, Margriet van Eikema Hommes, 2004. Archetype Publications, London. 6. Analytical chemical studies on traditional linseed oil paints, Jorrit D.J. van den Berg, 2002. ISBN 90-801704-7-X 7. Microspectroscopic analysis of traditional oil paint, Jaap van der Weerd, 2002. ISBN 90-801704-8-8 8. Laser desorption mass spectrometric studies of artist’s organic pigments, Nicolas Wyplosz, 2003. ISBN 90-77209-02-6 9. Molecular studies of Asphalt, Mummy and Kassel earth pigments: their characterization, identification and effect on the drying of traditional oil paint, Georgina M. Languri, 2004. ISBN 90-77209-07-7 10. Analysis of diterpenoid resins and polymers in paint media and varnishes; with an attached atlas of mass spectra, Klaas Jan van den Berg (forthcoming). 11. Binding medium, pigments and metal soaps characterized and localized in paint cross- sections, Katrien Keune, 2005. ISBN 90-77209-10-7 12. Paints quantified: image analytical studies of preparatory grounds used by Van Gogh, Beatrice Marino, 2006. ISBN-10 90-77209-19-6 ISBN-13 978-90-77209-19-6 13. Reporting highlights of the De Mayerne Program, research program on molecular studies in conservation and technical studies in art history, Jaap J. Boon and Ester S.B. Ferreira (editors), 2006. ISBN 90-77875-14-X 14. Color changes and chemical reactivity in seventeenth-century oil paintings, Annelies van Loon, 2008. ISBN/EAN 978-90-77209-17-2 Published MOLART reports can be ordered from Archetype Publications, 6 Fitzroy Square, London W1T 5HJ, UK, Tel: +44 207 380 0800 Fax: +44 207 380 0500, [email protected]. Photo credits Royal Picture Gallery Mauritshuis, The Hague Royal Collections, The Hague Margareta Svensson, Amsterdam Limburg Conservation Institute (SRAL), Maastricht State Building Agency (Rgd), The Hague Edwin Verweij, Amsterdam Mark Richter, Technical University Munich, Germany Kröller Müller Museum, Otterlo Staatliche Museen, Kassel, Germany Table of Contents Introduction 9 Chapter 1 Improving the Surface Quality of Paint Cross-sections for Analytical Imaging Studies with SR-FTIR and Static-SIMS 23 Chapter 2 The Relationship between Preservation and Technique in the Paintings of the Oranjezaal 43 Chapter 3 The Whitening of Bone Black in Oil Paint Films 93 Chapter 4 White Hazes and Surface Crusts on Dark Oil Paint Films 119 Chapter 5 Darkening as a result of Increased Transparency in 17thC Oil Paintings 205 Summary / Samenvatting 241 Dankwoord 257 About the Author 261 introduction Introduction color changes and chemical reactivity in traditional oil paintings Traditional oil paintings are not stable systems, and despite the fact that so many Old Master paintings are considered to be generally well preserved, the oil paint used by the seventeenth-century painters as discussed in this thesis is an extremely dynamic system, much more dynamic than is usually thought. Paintings are, in fact, subject to all kinds of chemical and physical processes taking place on a micro and molecular level in the paint layers that only over time (eventually) become visible changing the original appearance of the work of art. These processes are inherent to the artist’s choice of materials and his working methods. They are triggered or accelerated by external factors, such as light, moisture, heat, atmospheric pollutants, from display, storage or certain conservation and restoration interventions. Depending on the materials and the sorts of exposure these changes can be extreme or barely perceptible. Artists’ knowledge of materials can be inferred from historic sources. Seventeenth-century artists were generally well-educated professionals, who were organized in guilds in order to limit competition and to ensure the quality of work. Although they had a thorough knowledge of materials, commercial reasons also played a role in the choice of materials, production processes and speed with which paintings were produced. Artists were usually also well informed about the limited durability of some pigments, their knowledge corresponding with what we know today. Of course, they were not aware of all the possible paint defects that could occur, since some changes have only become visible after 50 or 100 years, or even longer. Historic sources reveal that of pigments and colorants used in traditional oil paintings, the red and yellow organic lake pigments, the blue organic colorant indigo, the blue cobalt-glass smalt, red lead, the blue/green copper pigment verdigris and lamp black were known to be the most problematic when used in oil. The organic pigments are susceptible to light fading, smalt paints have the tendency to turn brown or gray over time, red lead can grow lighter, verdigris glazes often become an opaque brown and lamp black may either darken or become whitish. The reason that they were still used predominantly lies with the limited choice or availability of pigments in that time. In other cases, economical reasons may have prevailed. In the historic recipes, various methods are described to prevent or minimize discoloration, such as limiting a light-sensitive pigment to the underpainting, bleaching the oil medium in the sunlight, substituting another type of binding medium, or the exclusive use of high quality materials [Van Eikema Hommes 2004]. The understanding of the painted work of art on a micro and molecular level has made considerable progression the past ten years partly due to the MOLART (1995-2002) and De Mayerne (2002-2006) NWO research programs, cooperative projects between scientists, conservators and art historians (see MOLART Reports), 10 but also to the development of analytical instrumentation and growing interest from the museums themselves for this kind of research. This knowledge has important consequences for the art historical interpretation of a painting, as well as for the preservation and presentation of the work of art. This thesis focuses on changes in appearance in seventeenth-century oil paintings as a result of natural ageing. It involves interdisciplinary research at the boundary of chemistry, conservation and art history. Interpretation problems that arose during restoration treatment of paintings formed the basis for much of the work. The case studies presented include paintings and painted ceilings from the Royal Picture Gallery Mauritshuis, the Oranjezaal ensemble in the Royal Palace Huis ten Bosch, the Johan de Witt house, the Trippenhuis, and the Staatliche Museen Kassel. They were examined in close collaboration with the conservators responsible for their care. The first chapter addresses the preparation of paint cross-sections and the various analytical techniques, mostly developed during the MOLART and De Mayerne programs for painting studies. Using the techniques as described in Chapter 1, the chemical and physical processes responsible for the degraded appearances of the paintings were investigated. The following four chapters deal with various degradation phenomena as encountered in seventeenth-century oil paintings. In the case of the unique ensemble of paintings of the Oranjezaal in the Royal Palace Huis ten Bosch, which was extensively investigated as part of this thesis, the paintings have remained in situ under known conditions with minimal intervention since 1650. The ensemble of 40 paintings offered a unique opportunity to investigate changes in appearance and ageing processes and relate them to other known materials and methods used by the various artists, since the external factors are similar.