UNIVERSIDADE DE LISBOA FACULDADE DE CIÊNCIAS DEPARTAMENTO DE QUÍMICA E BIOQUÍMICA MOLECULAR ASPECTS OF THE CHEMICAL DRYING OF OIL PAINTS FORMULATED IN THE PERIOD 1890-1940 Pedro Alexandre Santos Leitão Caetano Alves DOUTORAMENTO EM QUÍMICA (QUÍMICA) 2015 UNIVERSIDADE DE LISBOA FACULDADE DE CIÊNCIAS DEPARTAMENTO DE QUÍMICA E BIOQUÍMICA MOLECULAR ASPECTS OF THE CHEMICAL DRYING OF OIL PAINTS FORMULATED IN THE PERIOD 1890-1940 Pedro Alexandre Santos Leitão Caetano Alves Tese supervisionada pela Professora Doutora Maria Helena Ferreira da Silva Florêncio e pelo Professor Doutor Jaap J. Boon ESPECIALMENTE ELABORADA PARA OBTER O GRAU DE DOUTOR EM QUÍMICA (QUÍMICA) 2015 ACKNOWLEDGMENTS This work would never been possible without the help, guidance, encouragement, and belief of so many people that it’s hard not miss anyone who contributed in some way to the completion of this thesis. First I have to acknowledge my supervisors: Prof. Helena for accepting me as her PhD student on a project she had no idea of, for mentoring me always and gave me the liberty to learn from others in the conservation field, and for all the valuable lessons in Life and Mass Spectrometry, as well as in Analytical sciences in general; and to Prof Jaap Boon who I met personally in 2006 at the end of the De Mayerne Programs and who believed that I could be trusted with a project that was not far from what he had built up in the previous Molart program, for building a project that is somehow a gap in our knowledge and giving me the best advice during all these years now: “don’t try to reinvent the wheel” and “think critically”. Also for putting me in contact with world experts in conservation science all over, starting with Prof. Leslie Carlyle that was my “emeritus supervisor”, and was my supervisor at Tate Britain Conservation Science, she taught me endless details of conservation, and later when we both moved back to Lisbon, the endless hours of fruitful discussion, conferences, paper reviewing, guidance and the “focus” word, “you’ll have time for that at a Post-doc, Focus!” . While at Tate with Leslie, I had the pleasure of being able to share the Lab and critical thinking with Joyce Townsend (thank you for the samples on the Camden town artists), Stephan Hackney and Bronwyn Ormsby (thank you ever since, and the Py-GC/MS analysis) who were pretty much the high standard reference on conservation science. Also to Jacob Thomas, for my research help, my first account of PhD finishing at a close, while I was pressing Oils. But back home I had so many times the assistance and advice from my GEMAB group at FCUL, Prof. Carlos Borges (“we have a Book chapter!”), Prof. Filomena Duarte (“keep it simple”) and Prof. Teresa Fernandez, as well as the younger members that put up with me on a daily basis Pedro Vaz (FTIR doubts), now PhD Paulo Madeira ( I could never thank you enough for all that you taught me on MS, ion trap and FT-ICR, ESI or MALDI, thank you for being a friend “Daddy”) and Rita, Tiago and Tânia, the “young team” for all the help the Lab, always believing in my work, for being such good colleagues and great lunch times. While in Amsterdam I have to thank Klass Jan van der Berg, for accepting me at Netherlands Cultural Agency, and presenting me with a multidisciplinary and collaborative place aiming at building knowledge across science and art, and giving me access to the Technisches Mitteilungen fur Malerei whole archive. Also to the “basement people” Francesca Izzo (we will publish soon on Rodchenko samples), Beatriz and Alba Campo, for being such good people always with a smile. In Lisbon I was also collaborating with José de Figueiredo Conservation and Restoration Lab, this is where I fell in love with conservation science, back in 2001, and cannot leave them out of these acknowledgments because they are the reason I chose these field of work, where I developed my Masters and have always supported me: Prof. António Candeias, Engª Isabel Ribeiro, Ana Mesquita e Carmo, Lília Esteves, Zé Oliveira, Zé Carlos Frade, Sara Valadas, Milene Gil and all the good people from the conservation departments. I could not end this Thesis without my personal Friends, I’ll just say you know who you are, and a special thank you. To Sandra for the final push till the End. Aos meus Pais INDEX Acknowledgments Chapter 1 Introduction 1 Chapter 2 Critical Review 13 Chapter 3 Raw Materials 110 Chapter 4 Analytical Techniques 161 Chapter 5 Discussion & Conclusions 218 1 ARTIST’S OIL PAINT – CONTROVERSY & RESEARCH ABSTRACT This chapter reflects on the various perspectives of artist’s oil paint uses, with a focus on the research on oil. Since the empirically based formulation introduced by artist’s to the colourmen, to the science based developments in the raw materials, formulation, analysis and conservation science particularly. 1.1 INTRODUCTION There are extensive studies and general citations on the subject of oil paint studies, and vegetable oils. The most widely used siccative oil is, by far, Linseed oil (Linum usitatissimum) only to be followed by Poppy (Papaver somniferum) and walnut oils (Junglans Regia). But it is thought that by the turn of the 19th to early 20th century 1 there were changes introduced in artist’s oil paint formulation, mainly empirically, by colourmen which would affect Art works ever since. The main aspect we are here dealing with is the introduction of less siccative oils, the semi-drying or even non-drying oils, in unknown quantities, which not only prolongs the shelf life of tube oil paints but imparts new characteristics to the paint. Other possible consequences of these less drying formulations have been studied, in order to distinguish them from “normal” formulations, to understand the process of dripping paints, as a direct consequence of less drying starting materials. 1.2 A TECHNICAL DESCRIPTION OF OIL PAINT Historically artist’s oil Paint, as it has been used since early times, consists of a Binder, or Vehicle, and the pigment. These were ground together in a slab of Porfirus stone and collected with help of pallet knifes to be collected and stored in pig’s bladders before the introduction of paint collapsible tubes. The Pigments used are more or less described historically, ever since the first cave drawings to modern pigments, industrial and synthetic, inorganic and organic. As for the Binders less is known or at least less is agreed on unanimously, and this is why we are here reflecting on this subject. Although it did not change as much as the pigments, it changed from artist to artist and workshop to workshop manufacturer and colourmen. In a simple way, the oil binding media consisted of drying or siccative oil, named this way for the ability to form a dry film with time. 2 Not so common, and the objective of this study, is the use of semi-drying or nondrying oils, or simply other types of oil, that would replace partly or entirely Linseed oil. Drying oils are natural triacylglycerides (TAG’s) containing high percentage of polyunsaturated fatty acids that give these oils the property of air-drying. These polyunsaturated fatty acids readily oxidise to form a three-dimensional network by the oxidative polymerization mechanism of drying oils (we will return to this point). Most complex in the paint making is the addition of additives, and these could consist of a myriad of things, ranging from beeswax to resins, or fillers to driers of various sources, and these complex mixtures are extremely complicate analytical puzzles in chemistry. We will focus on the Binding media and it’s treatments for use in Oil Paint. 1.3 BRIEF HISTORY Historically artist’s oil Paint has been used since early times, it is known to been used since Egypt it’s is already mention in Treatises since Vitruvius Charles Eastlake did a good overview of past treatises, like Cennini [1], and presents a good summary in his “Materials for a History of Oil Painting” [2]. It would be exhaustive to present all the books related to this topic, like Field’s “Chromathography”[3], Bouvier, Merimeé [4], Chevreul[5], Tingry, Muckley [6] [7]and others, but Leslie Carlyle has a brilliant text, The Artist’s Assistant [8], which enumerates all of these to the 19th Century. There is also an extensive review on a 3 collection of texts in N.S Baer and N. Indictor “Linseed oil and related Materials: an annotated Bibliography” in three parts (Part I Antiquity to 1940; Part II from 1940 to 1960; Part III 1961-1972) Published by AATA)[9-11]. 1.4 A VIEWPOINT ON SOME CRITICISM Preface to Muckley[6] “Of the three fixed-oils considered most proper for the purposes of painting, to wit, Poppy, Nut and Linseed Oil, the first named is that which since its introduction to the art has taken the lead of all the rest, and might be said almost to be the only oil now used, certainly with us, both the others, and especially the last, having in comparison but few favorers; though Nut Oil is that which the Italians adopted, while Linseed had the preference of the Dutch and Flemings.” Bouvier, Pierre Louis [12] in Chapter IX p70 4 “Whether an oil might not be obtained of a drying quality and sufficient strength for oil painting which shall have the property of continuing permanently colorless remains for research. Yet, according to our present knowledge, it may be questioned whether oils do not uniformly change in color in proportion to their natural power of drying.