Multiscale approach in the assessment of nanocellulose-based materials as consolidants for painting canvases Alexandra Bridarolli Submitted for the degree of Doctor of Philosophy University College London Eastman Dental Institute August 2019 1 Abstract This thesis investigates mainly the use of nanocellulose-based treatment for the consolidation of degraded cotton canvases of modern paintings and includes within this some case studies on linen canvases (sized and unsized) and 19th cent. historical samples from paintings. It. uses a multi-scale analytical approach where primarily controlled relative humidity dynamic mechanical analysis (DMA-RH) was used to evaluate the effect of the novel nanocellulose based preparations. It aims at quantifying the advantages, disadvantages, and limitations of their application. Initially, the baseline viscoelastic response to RH variations of a degraded cotton canvas was measured by DMA-RH. This technique was used further together with SEM to assess morphologically and mechanically 6 traditional consolidants including natural such as animal glue and synthetic materials. Following the same protocol, two solutions of nanocellulose-based consolidants developed in the frame of the Nanorestart project were assessed. These materials consisted of nanocellulose dispersions in water or water/ethanol and nanocomposites of nanocellulose- reinforced cellulose derivatives in polar/apolar solvents. Overall, higher consolidation at lower weight added was measured for the nanocellulose-based treatments tested when compared to the traditional consolidants. The penetration of the consolidant in the canvas also shows to greatly differ between treatments with the nanocellulose showing low penetration. Higher mechanical response to RH was also measured after treatment in particular with the water-based treatment. The results demonstrate how the adhesion, measured here at the nanoscale, and consolidant penetration into the canvas are dominant factors for the development of consolidation treatment for painting canvases. The assessment of the novel consolidants was finally carried out on historical canvases. Most treatments show to perform well on historical paintings in terms of handling properties, penetration and surface appearance and consolidation. Preliminary time-resolved neutron radiography with new purpose built sample chamber and RH controller provided visual information on time-dependent moisture response of the samples. 2 Declaration I confirm that the work presented in this thesis is my own original work. When information has been derived from published work, it has been cited when appropriate. Results that have been published by my colleagues and me are also indicated. Samples obtained as a results of collaborations have been noted. Alexandra Bridarolli 3 Acknowledgements Firstly, I must extend my gratitude to my two supervisors, Dr Marianne Odlyha and Dr Laurent Bozec for their continued advice and support during the PhD. Without their support, this thesis would not be where it is today. Their consideration allowed me to pursue the varied topics found in this thesis. I must then thank my two other supervisors Dr Aurelia Chevalier and Dr Manfred Anders who I am grateful for their support, the recommendations they were able to give me throughout this PhD and the ideas that were raised during our discussions and exchanges. This research would not have been possible without funding from the H2020 Nanorestart European project and from the Engineering and physical Research Council (EPSRC) through the Centre for Doctoral Training In Science and Engineering in Arts, Heritage and Archeology. I should also thanks other partners from the Nanorestart project who have always been there when I needed help. For their help, support, friendship, open-minded attitude and curiosity, I would like to thanks in particular: Romain Bordes, Oleksandr Nechyporchuk, Marta Oriola, Nadine Böhme, Katharina Schumann, Katrien Keune and Giovanna Poggi. Because this PhD has shown me that research can sometimes be very competitive, I would first like to thank first John Duncan at Lacerta Technology for his unconditional support and help with the DMA. I also thank Dale Moulding at the Institute of Child Health UCL for his help with ImageJ and collaborators in Switzerland R. Fischer and Dr Mannes who have given their time to answer my very basic questions about neutron radiography. I would also like to thank collaborators at the institute of conservation of Copenhagen Dr Krarup Andersen and Dr Dorte Sommer and Dr René Larsen. All these people have showed me that research should always be driven by curiosity. For their time and help, I am grateful to Dr Nicky Mordan, Dr George Georgio, Dr Graham Palmer and Dr Isabel Kingston. I would not have known that much about Eastman and its devices without them. Because this PhD would have been far less special without it, I also thank the team at SEAHA. The first year of PhD has been the most challenging and exciting thanks to the lectures of Dr. Matija Strlic and Josep Grau-Bove and my colleagues Danae, Sarah, Vladimir, Mark, Isabella, Lucie, Scott and Nathalie. Finally, because life is not all about cultural heritage and conservation, my final words will be for my peers at the Eastman Dental Institute: Adam, Lucia, Ana, Nabih, Nazanin, Sarah, Mayda. There are many more people throughout UCL and London who provided their help. 4 Nanorestart European project This research project has been carried out in the frame of the European NANOrestart project which has been running from September 2014 to September 2018. As such, most of the materials and consolidants used in this project were provided by project partners. This includes the cotton canvas and the nanocellulose-based consolidants tested. The main collaborators of this research are cited below: - Romain Bordes and his research group at the Department of Chemical and Biological Engineering, Chalmers University (Gothenburg, Sweden) who provided with the nanocellulose dispersions and the treated degraded cotton canvas samples (solution 1 in Chapter 2) and consolidant consisting of multi-layered nanoparticles (solution 3 in Chapter 2) presented in Chapter 5 and 6. - Manfred Anders and his group at the Zentrum für Bucherhaltung (Leipzig, Germany) who provided the nanocomposite consolidants (solution 2 in Chapter 2). - Piero Baglioni and his research group at CSGI, University of Florence (Italy) who provided a consolidant consisting of multi-layered nanoparticles (solution 3 in Chapter 2) - Marta Oriola and her team at the Department of Fine Arts, University of Barcelona (Spain) who provided the cotton canvas and prepared the samples described in chapter 6. - Aurelia Chevalier from the Aurelia Chevalier Atelier (Paris, France) who participated in the research carried out in Chapter 7. 5 Impact statement This project has used a comprehensive nanometrology and mechanical approach to review the potential of new consolidants for the structural consolidation of canvas paintings supports. It is hoped that these treatments will offer an alternative to lining and consolidants currently in use and prevent the re-occurrence of the issues highlighted in the Greenwich conference. It is also expected that the results of this project will enable further research groups worldwide, from heritage scientists to conservators to consider the approach that we present in this manuscript to assess the performance of the materials used in conservation. This work in this thesis has been presented in approximately a dozen conferences, seminars, workshops and internal meetings of the Nanorestart European project, and published as 3 articles with several co-authors. One of the papers was published in a high impact factor journal as first author. Three more papers are currently under preparation. This research was also presented to larger, non-specialized audiences, at the Cheltenham Science festival as well as at the UK semi-final 3MT thesis competition which was also podcasted. The work in Chapters 4, 5 and 6 was performed in collaboration with other European institutions in the framework of the Nanorestart European project. Chapter 4 and 6 benefited from the close collaboration with professional painting conservators. Chapter 5 consists of the assessment of a range of canvas consolidants developed by research groups based in various universities and a private conservation centre. Part of the work presented in Chapter 5 was also carried out with two MRes students from Birkbeck University (University of London, UK). Several collaborations were also set up with other institutions. The work presented in Chapter 7 is the result of one of these collaborations. The study was successfully carried out at the neutron facility at ISIS (UK) and involved the participation of another group from the private company Lacerta Technology Ltd (UK). New collaborations were also started with heritage institutions such as the Munch Museum in Oslo and the school of conservation in Copenhagen. Samples from an original canvas used by the Norwegian painter Edvard Munch were obtained for further testing. Complementary analysis of samples of this thesis could also be obtained in the framework of the thesis of a 1st- year conservation student from the school of conservation in Copenhagen. 6 Scientific publications (1) Odlyha, M.; Lluveras-Tenorio, A.; Lucejko, J.J.; di Girolamo, F.; Hudziak, S.; Strange, A.; Bridarolli, A.; Bozec, L. Violin varnishes: microstructure and nanomechanical analysis. (To