Very few stone sculptures conserve their original polychromy nowadays so the exceptional condition presented by the oil paint film of the Tomb of Chancellor Villaespesa in the Cathedral of Tudela (Spain) here presented as case study suggested that both the chemical-mineral composition of the oil paint films and of the lithotypes chosen for the artists to be in contact with the polichromy, could be responsible for their unexpected durability. When the mechanisms governing these painted structures stability are not understood properly, conservation materials and methods and even environmental conditions can have a dramatic effect in their performance and compromise their stability in the long term. In this study, mock-ups simulating different oil paint layers on the sandstone of the case study have been prepared. Mock-ups with the same oil paint films on other substrates have been made for comparison purpose. After four years of natural ageing, the aggregation of lead and calcium carboxylates have been identified and characterized on some mock-ups by means of the combined use of UV-VIS light microscopy, SEM-EDX and micro FT-IR spectroscopy. pH and conductivity have been measured and monitorized both in the mock-ups and the case study. Saponification reactions, ionomer formation and carboxylate aggregation in lead white or minium oil paint films contributed to make them less acidic, less ionized, less hydrolyzed and less soluble after ageing sandstone or on pine wood at room environmental conditions for four years. The same given paint films became more acid and more ionized after ageing on a glass slide. Understanding the properties of such films, the chemical-physical mechanisms governing their adhesive and cohesive forces, and their surface pH is not easy. Mineral assemblages as well as the availability of ions in the substrate of a given oil paint film containing lead white or minium play a fundamental role in the eventual formation, migration and aggregation of lead and calcium carboxylates not only at their surface but also within the substrate-film interface. Furthermore, monitoring surface pH and conductivity as well as understanding solubility issues and the adhesion forces existing between soils, the paint layer and the substrate is needed when designing any conservation strategy to minimize risks and to preserve the balance acquired by these artworks in time. / Muy pocas esculturas pétreas conservan su policromía original. El excepcional estado en el se mantienen las películas pictóricas al óleo del caso de estudio de esta tesis doctoral (el Sepulcro de Villaespesa de la catedral de Tudela, Navarra, España) sugiere que tanto la composición químico-mineral de la roca seleccionada por sus escultores como la composición de las películas pictóricas al óleo con las que se policromó dicha piedra, podrían ser responsables de su inesperada durabilidad. En el transcurso de esta tesis doctoral se prepararon probetas con distintas películas pictóricas al óleo sobre la arenisca del caso de estudio. Para hacer un análisis comparativo también se prepararon probetas con las mismas películas sobre otros soportes. Se monitorizó el pH y la conductividad el caso de estudio así como de todas probetas. A través del uso combinado de microscopía óptica, SEM-EDX y micro espectroscopía FT-IR se estudió la formación y envejecimiento de las películas al óleo identificó y se caracterizó la agregación de carboxilatos de calcio y plomo en algunas de las películas pictóricas al óleo con pigmentos de plomo. En aquellas películas al óleo con albayalde o minio que envejecieron durante cuatro años sobre substratos de arenisca y madera de pino, las reacciones de saponificación, la formación de ionómeros y la agregación de carboxilatos contribuyeron a generar estratos pictóricos menos ácidos, menos ionizados, menos hidrolizados y menos solubles. Dichas películas pictóricas se tornaron más ácidas e ionizadas tras envejecer, en las mismas condiciones medioambientales, sobre vidrio de microscopio. La comprensión de los mecanismos físico-químicos que gobiernan no solo el pH y la conductividad sino también las fuerzas adhesivas y cohesivas de estas películas a lo largo del tiempo, no es sencilla. Tanto los agregados minerales como la disponibilidad de iones que presentan sus substratos juegan un papel fundamental en la eventual formación, migración y agregación de carboxilatos de calcio y plomo no solo en su superficie, sino también en la interfase substrato-película pictórica. Cuando los mecanismos que gobiernan los equilibrios físico-químicos de estos sistemas pictóricos no se comprenden adecuadamente, los materiales y métodos empleados en su conservación así como las condiciones medioambientales en las que se mantienen pueden tener un efecto dramático en el comportamiento de estos sistemas pictóricos y comprometer su estabilidad a largo plazo. / Molt poques escultures pètries conserven la seua policromia original. L'excepcional estat de conservación en que es conserven les policromies del cas d'estudi d'aquesta Tesi Doctoral (el Sepulcre de Villaespesa de la catedral de Tudela, Navarra, Espanya) sugereix que tant la composició química-mineral i la porositat de les roques seleccionades pels artistes com la composició de les pel·lícules pictòriques a l'oli que van preparar per a policromar la pedra, podrien ser responsables de la seua inesperada durabilitat. Quan els mecanismes que governen els seus equilibris fisicoquímics no han estat compresos adequadament, els materials i mètodes emprats en la seua conservació així com les condicions mediambientals en què es mantenen poden tinder un efecte dramatic al comportament d'aquests sistemes pictòrics i comprometre la seua estabilitat a llarg termini. En aquesta tesi es van preparar provetes amb diferents pel·lícules pictòriques a l'oli sobre l'arenisca emprada en el cas d'estudi. També es van preparar provetes amb les mateixes pel·lícules sobre altres suports per fer una anàlisi comparatiu. Després de quatre anys d'envelliment natural, es va identificar i caracteritzar l'agregació de carboxilats de calci i plom en algunes de les provetes a través de l'ús combinat de microscòpia òptica, SEM-EDX i micro espectroscòpia FT-IR. També es monitarizaren el pH i la conductivitat de les provetes així com del cas d'estudi. En aquelles pel·lícules a l'oli amb blanc de plom o mini que van envellir durant quatre anys sobre substrats de gres i fusta de pi, les reaccions de saponificació, la formació de ionómeros i l'agregació de carboxilats van contribuir a generar estrats pictòrics menys àcids, menys ionitzats, menys hidrolitzats i menys solubles. Aquestes pel·lícules pictòriques es van tornar més àcides i ionitzades després envellir, en les mateixes condicions mediambientals, sobre vidre de microscopi. La comprensió dels mecanismes fisicoquímics que governen el seu pH i la seua conductivitat així com les forces adhesives i cohesives d'aquestes pel·lícules al llarg del temps no és senzilla. Tant els agregats minerals com la disponibilitat de ions que presenten els seus substrats juguen un paper fonamental en l'eventual formació, migració i agregació de carboxilats de calci i plom no només en la seua superfície, sinó també en la interfase substrat-pel·lícula pictòrica. / Aguado Guardiola, E. (2017). Estudio del rol de los agregados minerales en la formación, envejecimiento y conservación de películas pictóricas al óleo [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90462

In this thesis, geometry is used as a basis for conducting experiments aimed at growing and arranging inorganic minerals on curved interfaces. Mineralisation is directed using crystalline and liquid-crystalline metallic soaps and surfactant/water systems as templates.¶ A review of the history, syntheses, structure and liquid crystallinity of metallic soaps and other amphiphiles is presented as a foundation to understanding the interfacial architectures in mesostructured template systems in general.¶ In this study, a range of metallic soaps of varying chain length and cation type are synthesised and characterised to find potentially useful templates for mineral growth. These include alkaline-earth, transition metal, heavy metal and lanthanide soaps. These are systematically characterised using a variety of analytical techniques, including chemical analyses, x-ray diffraction (XRD) infrared spectroscopy (IR) and differential scanning calorimetry (DSC). Their molecular and crystal structures are studied using transmission electron microscopy (TEM), cryo-TEM, electron diffraction (ED), electron paramagnetic spin resonance (EPR), absorption spectroscopy (UV-VIS), high resolution laser spectroscopy, atomic force microscopy (AFM), nuclear magnetic resonance spectroscopy, scanning electron microscopy (SEM), electron dispersive x-ray analysis (EDXA), thermal gravimetric analysis (TGA) and magnetic measurements. Models for the molecular and crystal structures of metallic soaps are proposed. The soaps are predominantly lamellar crystalline or liquid crystalline lamellar rotor phases with tilted and/or untilted molecular constituents. These display evidence of varying degrees of headgroup organisation, including superstructuring and polymerisation. A single crystal structure is presented for a complex of pyridine with cobalt soap. Simple models for their structure are discussed in terms of their swelling properties in water and oils. Experiments are also presented to demonstrate the sorbent properties of aluminium soaps on oil spills.¶ The thermotropic liquid crystallinity of alkaline earth, transition metal, heavy metal and lanthanide soaps is investigated in detail. This is done to assess their suitability as templates, and to document their novel thermotropic behaviour, particularly the relatively unknown lanthanide soaps. Liquid crystalline behaviours are studied using high-temperature XRD (HTXRD), hot-stage optical microscopy and DSC. Models for a liquid crystalline phase progression from crystals to anisotropic liquids are discussed in terms of theories of self-assembly and interfacial curvature. The terminology required for this is drawn from various nomenclature systems for amphiphilic crystals and liquid crystals. General agreement with previous studies is reported for known soaps, while liquid crystallinity is demonstrated in the lanthanide and some non-lanthanide soaps for the first time. A general phase progression of crystalline lamellar through liquid crystalline lamellar to non-lamellar liquid crystalline is discussed in terms of models concerned with the molecular and crystal structures of the soaps and their phase transitions via headgroup and chain re-arrangements.¶ Experiments aimed at guiding growth of metal sulfides using metallic soaps as templates are described, and a model for this growth is discussed. Metal sulfides have been successfully grown by reacting crystalline and liquid crystalline transition metal and heavy metal soaps with H2S gas at room temperature and at elevated temperature. These have been characterised using XRD, TEM, ED and IR. Sulfide growth is demonstrated to be restricted and guided by the reacting soap template architecture. Zinc, cadmium, indium and lead soaps formed confined nanoparticles within the matrix of their reacting soap template. In contrast, curved and flat sheet-like structures, some resembling sponges were found in the products of sulfided iron, cobalt, nickel, copper, tin and bismuth soaps. A model to explain this behaviour is developed in terms of the crystal and liquid crystal structures of the soaps and the crystal structures of the metal sulfide particles.¶ Liquid crystalline iron soaps have been subjected to controlled thermal degradation yielding magnetic iron oxide nanoparticles. Some XRD and TEM evidence has been found for formation of magnetic mesostructures in heat-treated iron soaps. Models for the molecular and liquid crystalline structure of iron soaps, their thermotropic phase progression and eventual conversion to these magnetic products are discussed. Systematic syntheses of mesoporous silicates from sheeted clays are discussed.¶The templates that have been used are cationic surfactants and small, organic molecular salts. Experiments are reported where a cooperative self-assembly of surfactant/water/kanemite plus or minus salt and oils yields 'folded sheet materials' (FSM'S). Templating of kanemite has also been achieved using cobalt cage surfactants. A theoretical prediction of the specific surface areas and specific volumes of homologous sets of FSM's gave excellent agreement with measured values. The geometry and topology of the mesostructures are discussed. A theoretical model is also discussed regarding the curvature found in the sheets of natural clays , and results of templating clays and silica using metallic soaps are presented. Experiments and a model for low temperature nucleation and growth of microporous silicalite-1 are described in terms of silica templating by water clathrates.¶ Finally, the problem of finding minimal surface descriptions of crystal networks is addressed. Combinatoric methods are used to disprove the existence of possible embeddings of type I and II clathrate networks in non-self intersecting periodic minimal surfaces. The crystal network of the clathrate silicate, melanophlogite is successfully embedded in the WI-10 self-intersecting surface. Details of a previously unreported, genus-25 periodic surface with symmetry Im3m are discussed.