The conservation of panel paintings and related objects The conservationResearch agenda 2014 -2020 of panel paintings and related objects Britta New The Painted Support: Properties and Behaviour of Wood CHAPTER 2 2014 -2020 Research agenda 2014 -2020 The conservation of panel paintings and related objects 1 Research agenda CHAPTER 2 2 The conservation of panel paintings and related objects The Painted Support: Properties and Behaviour of Wood Research agenda 2014 -2020 Britta New The conservation of panel paintings and related objects Research agenda 2014 -2020 Britta New The Painted Support: Properties and Behaviour of Wood CHAPTER 2 Research agenda 2014 -2020 The conservation of panel paintings and related objects 3 4 4 The conservationofpanelpaintingsandrelatedobjects Research agenda2014-2020 2014 -2020 Britta New The PaintedSupport:PropertiesandBehaviourofWood CHAPTER 2 Research agenda and related objects of panel paintings The conservation . .. from the Getty Foundation as part of the Panel Paintings Initiative. from theGettyFoundationaspartofPanelPaintingsInitiative. Scientific ResearchandtheRijksmuseumAmsterdamwithgrantsupport This reportwaspreparedattherequestofNetherlandsOrganisationfor Research agenda 2014 -2020 Britta New The conservation of panel paintings and related objects The Painted Support: Properties and Behaviour of Wood 5 CHAPTER 2 Contents Summary 8 1. Introduction 11 1.a The panel painting 13 1.b. Background to the report 14 2. The Painted Support: Properties and Behaviour of Wood 17 2.a. Construction of a Panel Painting 19 2.b. Fundamentals of Wood Structure 20 2.c. Damage Observed in Wooden Panels 32 2.d. The Role of Climatic Conditions 44 2.e. Current Conservation Practise 46 2.f. CONTENTS The conservation of panel paintings and related objects Research agenda 2014 -2020 Conclusions 57 2.g. Research questions 59 2.h. References 61 3. The painted surface and interface 73 3.a. Types of damage 77 3.b. The interaction of layers and adhesion 77 3.c. Review of Research 78 3.d. Research questions 82 3.e. References 85 4. Adhesives, consolidants, coatings 91 4.a. The hows and whys of adhesion 93 4.b. The nature of wood as an adherend 99 4.c. Conservation reports 102 4.d. Insights required for designing conservation applications 105 4.e. Conclusions 107 4.f. Research questions 109 4.g. References 111 The conservation of panel paintings and related objects Research agenda 2014 -2020 6 5. Acquisition of Information 117 5.a. Population Studies 119 5.b. Modelling 120 5.c. Methods & Imaging 122 5.d. Conclusions 131 5.e. Research questions 132 5.f References 133 6. Knowledge dissemination and education 139 6.a. Knowledge and skills requirements 142 6.b. Knowledge dissemination 148 6.c. Project Planning, Proprietary Materials, and Advanced Technology 156 6.d. Future desired outcomes 157 Research agenda 2014-2020 The conservation of panel paintings and related objects CONTENTS 6.e. Future Research questions 161 6.f. Relevant Journals and References 163 7. Conclusions 169 Appendices 1. Glossary 178 2. Proceedings of the expert meeting, 9-11 January 2011 190 3. Author biographies 206 Participants in the expert meeting 9-11 January 2011, Amsterdam 212 Acknowledgements 222 Colophon 224 Abstracts of relevant literature can be found at: www.nwo.nl/science4arts Research agenda 2014 -2020 The conservation of panel paintings and related objects 7 Summary Until the early 17th century almost all portable paintings were created on wood supports, including masterpieces by famous painters, ranging from Giotto to Dürer to Rembrandt. The structural conservation of these paintings requires specific knowledge and skills as the supports are susceptible to damage caused by unstable environmental conditions. Unfortunately, past structural interventions often caused significant damage due to insufficient knowledge of the behaviour of the wood panels, glue and paint layers. Over the last fifty years, the field has developed treatment strategies based on interdisciplinary collaboration and on the knowledge of specialist conserva- SUMMARY The conservation of panel paintings and related objects Research agenda 2014 -2020 tors. Most current conservation protocols rely on empirical knowledge of conser- vators and are not necessarily based on a scientific understanding of the nature and behaviour of wood and paint layers. In order to move the field forward, it is imperative to strengthen scientific research into the production methods, ageing and future behaviour of panel paintings, being an intricate interplay between different materials. A deeper understanding of the processes that adversely affect panel paintings over time will contribute to the improved care and conservation of these artworks. The Netherlands Organisation for Scientific Research (NWO) and the Rijksmuseum Amsterdam brought together a group of experts from different disciplines to recommend specific areas in the field that would benefit from systematic research. The experts concluded that targeted interdisciplinary research projects are key to understanding the behaviour of panel paintings and help conservators make better informed decisions. Research into chemical and physical properties of wood, glue and paint layers should be combined with an evaluation of past and current conservation treatments. Research should also consider the history of the object, studio practice, conservation history and thoughts on long-term impact of treatments. The conservation of panel paintings and related objects Research agenda 2014 -2020 8 Over the next seven to ten years key research topics should include: _ Hydromechanical properties of ageing wood in panels, _ Interlaminar stresses and fractures mechanics, also affecting the paint layers _ Loss of adhesion among the paint layers, _ Adhesives with appropriate chemical and physical properties, _ Non-destructive testing and development of theoretical models. Successful projects encourage close collaboration between conservators and (conservation) scientists, as each discipline brings a unique perspective to the discussion. This collaboration would include the review of existing literature, the development of a database with population studies, and the establishment of a calibration system between laboratories. Given the growing need for skilled conservators with a good scientific background, it is imperative that outcomes are widely shared with the conservation community. Wide dissemination can only be achieved with the support of national and interna- tional funding organisations, e.g. in the framework of the European Joint Pro- gramming Initiative on Cultural Heritage. Research agenda 2014 -2020 The conservation of panel paintings and related objects SUMMARY Strengthened collaboration among international stakeholders, concerned with the conservation of panel paintings, is vital to the advancement of the field. Existing programmes in a number of countries offer a useful basis, such as the Getty Panel Paintings Initiative and the NWO-programme Science4Arts. Museums, conservation institutes, cultural heritage institutions and universities must play an important role in promoting best practices, knowledge dissemination, and education. These organizations must take the lead to establish an international network of knowledge centres with open access policies that will stimulate knowledge transfer. Research agenda 2014 -2020 The conservation of panel paintings and related objects 9 CHAPTER 1 10 The conservation of panel paintings and related objects Introduction Research agenda 2014 -2020 Nico Kos and Paul van Duin 1. Introduction Research agenda 2014 -2020 Britta New The conservation of panel paintings and related objects The Painted Support: Properties and Behaviour of Wood 11 CHAPTER 2 Introduction 1. CHAPTER 1 12 The conservation of panel paintings and related objects Introduction Research agenda 2014 -2020 Nico Kos and Paul van Duin 1. Introduction 1.a. The panel painting For centuries wood was used as a common material for a variety of artworks, ranging from Egyptian Fayum coffin portraits to Old Master paintings. Unique masterpieces are painted on wooden panels. The Ghent Altarpiece by Van Eyck (1432) is just one fine example, but equally important objects can be found in many countries. Panel paintings are constructed from wooden boards, joined together by glue, dowels, and crosspieces. The painted surface of a panel typically has an interface of fabric and/or gesso that carries the paint layers, on one or both sides of the panel. Nico Kos and Paul van Duin Introduction CHAPTER 1 While wood can be a long-lasting material, it is unstable material and over time will show signs of deterioration, such as warping, splitting, and cracking. Mechanical and/or chemical degradation often results in damage, such as the detachment of the ground- and paint layers and loss of paint, and are generally the primary impetus for intervention. Most information on degradation processes is empirical. In the past a lack of knowledge of the consequences of treatments has sometimes led to irreversible damage (e.g. wash boarding). This has been aggravated by the adverse climate conditions under which panels are sometimes kept. There is, as yet, a lack of sufficient scientific research into the properties of ageing wood and its chemical and physical interactions with paint layers. This should deepen the understanding of these processes and the consequences of ageing and of interventions. Also the conservators’ knowledge of the production, the studio practice,