Auswahl der wissenschaftlichen Literatur zum Thema „Siccative oils“

A stony sculptural composition of the Nativity Scene is preserved in Altamura’s Cathedral (Apulia, Italy). This commonly called Apulian “presepe”, attributed to an unknown stonemason, is composed of polychrome carbonate white stone sculptures. While earlier stratigraphic tests have unveiled a complex superimposition of painting layers—meaning that several editions of the sculptures succeeded from the 16th to 20th century—a chemical investigation intended to identify the organic binding media used in painting layers was undertaken. Drawing on current literature, two strategies were exploited: a non-invasive in situ digestion analysis and an approach based on micro-removal of painting film followed by the Bligh and Dyer extraction protocol. Both peptide and lipid mixtures were analyzed by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and reversed-phase liquid chromatography coupled to mass spectrometry by electrospray ionization (RPLC-ESI-MS). Attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) examinations were also performed on micro-samples of painting films before lipids and proteins extraction. While human keratins were found to be common contaminants of the artwork’s surfaces, traces of animal collagen, siccative oils, and egg white proteins were evidenced in different sampling zones of the sculptures, thus suggesting the use of non-homogeneous painting techniques in the colored layers.

The most widespread varnish formulations used by master violin-makers of the “Italian Golden Age”, including Antonio Stradivari, were based on mixtures of siccative oils (e.g., linseed oil) and natural resins (e.g., colophony). Similar formulations are still used for the finish of contemporary instruments. Although most precious violins made by Stradivari and other Cremonese Masters are kept in museums, several instruments are still played and their finish may undergo deterioration due to contact with the players. Moreover, the decay of the traditional varnish may occur due to mechanical stress and natural aging caused by environmental agents (e.g., exposure to uncontrolled light, humidity, and temperature changes). The main aim of this research work is to investigate the possible improvement of varnish resistance to the decay induced by different aging processes. For this purpose, the traditional varnish (linseed oil/colophony 3:1 w/w) was recreated in the laboratory following an ancient recipe and then it was functionalized with a cross-linking agent (3-Glycidyloxypropyltrimethoxysilane, GLYMO). Plain and functionalized varnishes underwent artificial aging (UV light, temperature, and humidity variations), and their properties were comparatively studied using different techniques. All the results suggest that the functionalized varnish displays improved resistance to the aging process and particularly enhanced photostability and increased hardness (resistance to scratches).

The object of this paper is the diagnostic campaign performed on the polychrome wooden statue, revered as St. John, stored in the church dedicated to the “Beata Vergine d’Itria” (Blessed Virgin of Itria), (Noragugume town, Sardinia, Italy). The restoration of the statue gave the occasion to investigate micro-samples from the wooden support and from the polychromy in order to gather information that could be useful for the intervention. In fact, there was limited information on this fine carved statue and its iconographic pattern appeared to be not strictly canonical. Moreover, these kinds of artworks, having religious significant for the faithful, have been generally modified over time to satisfy possible changes in artistic or religious needs or ecclesiastical reforms. The aims of this study are: (i) support the restorers in defining the conservation status of the statue, and (ii) perform a series of analyses to identify the wood and the materials of the painting layers. Specifically, wood micro-sample was examined under the microscope in order to investigate the anatomical characteristics useful to identify the species; pigments were studied through X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS); organic materials were analysed by Fourier transform infrared spectroscopy (FTIR); and, lastly, the panting technique was investigated through micro-stratigraphy (MS). The analysis performed on the micro-sample taken from the support allowed for identifying the wood as poplar. XRF detected chemical elements that could be associated to pigments such as azurite, blue smalt, red lead, white lead and ochres, and Au for the gilding. SEM-EDS confirmed these pigments and allowed to find also other elements useful to suggest the presence of further materials such as Ag in the metal foil. FTIR detected proteinaceous binder and siccative oils that were mapped in the micro-stratigraphy by using histochemical tests. All this information was used by the restorers to address the intervention from the cleaning to the final retouching.

In this work, we studied the manufacturing processes and the conservation state of gilt and painted leather fragments from Palazzo Chigi in Ariccia (Italy) by using different analytical techniques. Leather fragments present a silver leaf superimposed onto leather support. A gold varnish and different painted layers decorate it all. A top-down analytical approach was used to investigate this complex multilayer structure, which adopted techniques with different sampling depths. Organic and inorganic constitutive materials together with related degradation products were studied by time of flight secondary ion mass spectrometry (ToF-SIMS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and macro X-ray fluorescence (MA-XRF). The findings have revealed the presence of different elements and species as calcium and iron in the leather support, which was attributed to the un-hairing process in the leather tanning. Regarding what concerns the silver leaf, where the varnish cracked, silver chlorides, oxides, and sulfides were detected as degradation products of the silver leaf. Proteinaceous compounds were also identified where the silver leaf is unprotected by the varnish. These ion signals reveal a potential use of animal glue on both sides of the silver leaf to promote durable adhesion. In the gold varnish, the surface analysis revealed organic compounds such as resins and oils. In particular, the copresence of linoleic, arachidonic, and lignoceric acid ion signals in the yellow area suggests the use of aloe as a colorant. Lead ions in the same area were detected and attributed to the use of lead as siccative. Blue areas were obtained by using indigo and lead white in addition to an oil binder. This is confirmed by the detection of indigotin, fatty acid, and lead soap ion signals. A copper-based pigment was used to depict the green areas and copper oxalates were identified as its degradation products. Lastly, no significant information about the red colorant was obtained. Colophony is present as a component of the final varnish.

L'analyse approfondie des biens patrimoniaux est cruciale pour aider à leur préservation et protection. Elle exige des compétences variées, notamment dans le cas des œuvres d'art pour lesquelles une connaissance de leur contexte historique et de leur composition chimique est nécessaire. La restauration ou conservation de peintures anciennes présente ainsi de grands défis du fait de la complexité chimique du matériau considéré, des transformations qu'il a pu subir au fil du temps et de la disponibilité limitée des échantillons. Dans sa thèse (Sorbonne Université, 2022), C. Bouvier a démontré que l'imagerie par spectrométrie de masse ToF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) était une méthode pertinente pour étudier les processus de vieillissement dans les peintures anciennes. Des coupes stratigraphiques de peinture étudiées à une très haute résolution spatiale ont révélé des informations sur les processus chimiques mis en jeu. Cependant, le grand nombre de composés présents dans ces échantillons a rendu difficile l'interprétation des spectres de masse, en particulier la compréhension des processus de dégradation des huiles siccatives utilisées comme liants dans les tableaux. Ce travail de thèse a visé au développement d'une approche combinée d'analyse afin de pallier à ces limites et permettre l'identification approfondie de coupes stratigraphiques de peintures, en s'intéressant en particulier à la caractérisation de composés polymères organiques présents dans les résines naturelles et les huiles siccatives des peintures. La stratégie expérimentale choisie a d'abord consisté à analyser des références de résines par Py-GC×GC MS (Pyrolysis-comprehensive two-dimensional gas chromatography-mass spectrometry) pour identifier les marqueurs de résines diterpéniques et triterpéniques. Des composés jusque-là non détectés ont pu être mis en évidence et ont ensuite été utilisés pour permettre la distinction de résines dans des spectres ToF-SIMS. Une méthode GC-MS a ensuite été développée pour quantifier diverses huiles siccatives. Ces résultats ont validé des mesures ToF-SIMS de la littérature des rapports d'intensité d'acides gras, démontrant ainsi la capacité de l'approche à caractériser de façon fiable les processus de vieillissement des peintures. Cette approche a de plus permis l'analyse des espèces chimiques présentes dans les siccatifs en fonction de la profondeur de la couche picturale, la teneur initiale en siccatif et le temps de vieillissement. Les résultats obtenus ont permis l'analyse TOF-SIMS d'échantillons complexes. Une maquette de vernis (mélange résine-huile) a été préparée et analysée à différents stades de dégradation sous lumière en environnement contrôlé, ainsi que des prélèvements historiques provenant d'une peinture de la Renaissance et d'un pastel. L'objectif était de déterminer les causes de dégradation et la composition chimique de ces échantillons. Des analyses spectroscopiques complémentaires, notamment la spectroscopie infrarouge photothermique optique (O-PTIR) et la microscopie électronique à balayage (MEB), ont été employées pour appuyer ces résultats. L'existence de différentes voies de dégradation a finalement pu être établie pour le tableau de la Renaissance italienne et les données expérimentales ont permis de confirmer certains procédés décrits dans les traités de fabrication de pastels grâce à la détermination de la composition d'un prélèvement. En conclusion, l'association Py-GC×GC-MS/imagerie ToF-SIMS a été utilisée pour la première fois dans ce travail de thèse. Les résultats obtenus ont démontré la pertinence de cette approche multimodale pour une compréhension approfondie des processus de vieillissement des huiles siccatives. Ces travaux ont permis d'enrichir de façon significative la base de données existante pour l'identification des constituants organiques dans les peintures anciennes
A detailed analysis of cultural heritage work is crucial for their preservation and protection. This task requires a wide range of skills, especially in the case of artworks, where knowledge of their historical context and chemical composition is essential. The restoration or conservation of old paintings presents significant challenges due to the chemical complexity of the materials involved, the transformations they may have undergone over time, and the limited availability of samples. In her Ph.D. thesis (Sorbonne University, 2022), C. Bouvier demonstrated that imaging through ToF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) is a relevant method for studying aging processes in old paintings. Cross-sections of paint analysed at very high spatial resolution revealed valuable information on the underlying chemical processes. However, the vast number of compounds present in these samples made mass spectra interpretation challenging, especially in understanding the degradation processes of drying oils used as binders in paintings. This thesis aimed to develop a combined analytical approach to overcome these limitations and enable a more in-depth identification of paint cross-sections, focusing specifically on the characterisation of organic polymer compounds present in the natural resins and drying oils of the paintings. The chosen experimental strategy first involved analysing resin references by Py-GC×GC-MS (Pyrolysis-comprehensive two-dimensional gas chromatography-mass spectrometry) to identify markers for diterpenic and triterpenic resins. Previously undetected compounds were revealed and subsequently used to differentiate resins in ToF-SIMS spectra. A GC-MS method was then developed to quantify various drying oils. These results validated ToF-SIMS measurements from the literature based on fatty acid intensity ratios, demonstrating the approach's reliability in characterising the aging processes in paintings. Additionally, this approach enabled the analysis of chemical species in drying agents as a function of the depth of the paint layer, the initial content of the drying agent, and the aging time. The obtained results facilitated the ToF-SIMS analysis of complex samples. A varnish model (resin-oil mixture) was prepared and analysed at different stages of light-induced degradation in a controlled environment, alongside historical samples from a Renaissance painting and a pastel. The objective was to determine the causes of degradation and the chemical composition of these samples. Complementary spectroscopic analyses, including Optical PhotoThermal InfraRed spectroscopy (O-PTIR) and Scanning Electron Microscopy (SEM), were employed to support these results. Different degradation pathways were eventually established for the Italian Renaissance painting, and experimental data confirmed certain processes described in pastel manufacturing treatises by determining the composition of a sample. In conclusion, the combination of Py-GC×GC-MS and ToF-SIMS imaging was employed for the first time in this thesis. The results demonstrated the relevance of this multimodal approach for a comprehensive understanding of the aging processes in drying oils. This work significantly enriched the existing database for identifying organic constituents in old paintings

À partir du XVe siècle, les peintres préparent leurs peintures en broyant les pigments en présence d’huiles siccatives, comme l’huile de lin. Cette dernière constitue le liant, et forme un film solide après un long temps d’exposition à l’air. Afin d’accélérer le processus de séchage, il était d’usage pour les peintres de traiter leurs huiles avant d’y adjoindre des pigments. De nombreuses recettes historiques recommandent de chauffer les huiles en présence d’oxydes métalliques, appelés siccatifs. Parmi eux, l’oxyde de plomb (II) PbO était le plus fréquemment utilisé. En complément, de l’eau pouvait être ajoutée dans le milieu réactionnel. De tels traitements modifient la composition chimique des systèmes : les triglycérides de l’huile sont partiellement saponifiés et des savons de plomb sont formés. Simultanément, les propriétés physico-chimiques des huiles (consistance, couleur) évoluent. Ce travail vise à préciser les changements induits par le pré-traitement des huiles et à en comprendre l’origine. Dans ce but, les recettes historiques ont été transcrites en un protocole de formulation reproductible. Dans un second temps, la caractérisation des huiles traitées obtenues a été effectuée aux trois échelles : macroscopique, mésoscopique et moléculaire. L’impact de la quantité initiale de PbO (de 0 à 50% mol) et de l’ajout d’eau a été étudié. À l’échelle macroscopique, les propriétés rhéologiques sont fortement modifiées : l’huile seule, initialement newtonienne, voit sa viscosité augmenter avec la teneur en savons de plomb. Au-delà de 50% de PbO, les huiles saponifiées sont rhéofluidifiantes. L’échantillon d’huile chauffé avec 50% de PbO est également viscoélastique. À l'échelle supramoléculaire, des analyses SAXS et cryo-TEM ont révélé la présence de domaines lamellaires dispersés dans une matrice non organisée. La teneur en savons de plomb a un impact sur l’étendue et la distance caractéristique des domaines lamellaires. Afin de comprendre l’impact du cisaillement sur la structuration lamellaire identifiée au repos, les échantillons ont ensuite été analysés en rhéo-SAXS avec un faisceau synchrotron. Sous cisaillement continu, les lamelles ont adopté une orientation préférentielle dite parallèle. Un délaminage progressif a également été observé, plus marqué pour les échantillons les plus saponifiés. De manière surprenante, le cisaillement oscillatoire de l’échantillon viscoélastique a induit la formation de cylindres unilamellaires alignés dans le plan de cisaillement, conjointement à une diminution de l’élasticité de l’échantillon. En parallèle, l’influence de l’ajout d’eau au cours du chauffage a été étudiée : un déphasage progressif des échantillons a été observé, et les deux phases ont été caractérisées aux trois échelles. La caractérisation fine de la composition chimique des huiles saponifiées s’est avérée délicate mais a mis en évidence la grande diversité des espèces présentes dans les huiles traitées (savons, triglycérides partiellement saponifiés, chaînes aliphatiques isomérisées, cyclisées, etc.), et ce en raison des nombreux mécanismes réactionnels impliqués lors du chauffage. Aborder les huiles saponifiées selon une approche multi-échelles apporte un éclairage nouveau sur ce type de matériaux : le lien entre structuration supramoléculaire et comportement rhéologique a clairement été établi. La reconstitution de recettes historiques d'huiles chauffées en présence de PbO et l'utilisation de techniques analytiques complémentaires nous permet de mieux comprendre les pratiques picturales en usage à partir du XVe siècle. Afin d’affiner encore notre connaissance de ces systèmes, l’étude des huiles saponifiées au cours du séchage gagnerait à être poursuivie. Les observations faites sur les systèmes liquides pourraient ainsi être reliées aux altérations constatées à long terme sur les œuvres d’art
Since the 15th century, artistic painters have prepared paint mixtures by adding oil binders to various pigments. Oils commonly used in historical paints, such as linseed oil, are called drying oils: they exhibit natural hardening properties after a long period of exposure to air. To accelerate the drying process, numerous historical recipes mention the use of inorganic drying compounds (or “driers”). Among them, lead (II) oxide PbO was the most frequently used. The driers were ground, added to the oil and the mixture was heated, possibly with water. Such treatments modify the chemical composition of the systems: the triglycerides of the oil are partially saponified and lead soaps are formed. Simultaneously, the physicochemical properties of the oils (consistency, color) change. This work aims to detail the changes induced by the pre-treatment of oils and to understand their origin. To do so, the historical recipes were first translated into a reproducible formulation protocol. In a second step, the characterization of the obtained treated oils was performed at the macroscopic, mesoscopic and molecular scales. The impact of the initial amount of PbO (from 0 to 50 mol%) and of the addition of water were studied. On a macroscopic scale, the rheological properties are significantly modified: oils cooked with 0 to 31% PbO behaved like Newtonian fluids. With 50% PbO, metal soaps induced important modifications of the rheological properties, leading to viscoelastic systems with shear-thinning behavior. At the supramolecular scale, SAXS and cryo-TEM analyses revealed the presence of lamellar domains dispersed in an unorganized matrix. The lead soap content has an impact on the extent and on the characteristic distance of the lamellar domains. To understand the impact of shear on the lamellar structuring identified at rest, the samples were then analyzed by rheo-SAXS on a synchrotron beamline. Continuous shear led to a preferential parallel orientation of the lamellae. A progressive delamination was also observed, increasingly marked for the most saponified samples. Surprisingly, an oscillatory shear on the viscoelastic sample induced the formation of unilamellar cylinders aligned in the shear plane, together with a decrease in the elasticity of the sample. In parallel, the influence of the addition of water during heating was studied: a progressive demixing of the samples was observed, and the two phases were analyzed. The fine characterization of the chemical composition of the saponified oils proved to be arduous but highlighted the great diversity of species present in the treated oils (soaps, partially saponified triglycerides, isomerized and cyclized aliphatic chains, etc.), due to the numerous reaction mechanisms involved during heating. The multi-scale approach applied to saponified oils sheds new light on this type of material: the link between supramolecular structuring and rheological behavior has been clearly established. The reconstitution of historical recipes of oils heated with PbO and the use of complementary analytical techniques allow us to better understand the pictorial practices in use from the 15th century. In order to further refine our knowledge of these systems, the study of saponified oils during drying would require further research. Observations performed on the liquid systems could thus be correlated with the alterations that occur on the works of art in the long term

New formulations for processing pine wood based on vegetable oil waste using nanoscale magnesium oxide have been studied. As a filler in the composition of impregnating compositions, coniferous wood flour was used in an amount from 1 to 3%, as well as magnesium oxide nanopowder in a dosage from 0.01 to 0.1%. Processing pine wood with compositions based on vegetable oil with additives of magnesium oxide allows to improve the hydrophobic properties of the wood surface, reduce its swelling, moisture and water absorption. The most optimal parameters were obtained from wood samples treated with a composition containing 1% wood flour, 0.01% magnesium oxide and 1% siccative.

The study of the surface tension of wood of various tree species impregnated with used sunflower oil was carried out. Samples of birch, pine and linden wood were used for oil treatment. Impregnation of wood materials was carried out by the method of “hot-cold baths”. As an impregnating material, used refined fryer oil was used. In more detail, the paper examines the effect of an impregnating composition based on used fryer oil, with a filler and a desiccant on birch wood. Wood flour of coniferous wood species and a metal salt-based drier were used as a filler. The surface tension for all images was determined by the edge angle of wetting. For this purpose, the method of a liquid drop on the surface of a solid body was used. It was found that the impregnation of untreated wood with deep-frying oil leads to an increase in the surface tension on all samples, to a greater extent this is typical for pine wood. The introduction of a 1% siccative in the impregnating composition together with wood flour reduces the drying time and improves the water-repellent properties of birch wood.

The purpose of this work was to develop and study new safe formulations for wood processing based on used vegetable oil. The waste of refined vegetable oil, which remains after cooking, was used as the modifying base of the developed compositions. Impregnation of wood samples of standard sizes was carried out by the method of “hot-cold baths”. Starch was used as a filler, and a precipitated type NF-1 desiccant was used to accelerate the drying of the applied compositions. The properties of wood were controlled by changes in such indicators as water absorption, as well as swelling in the radial and tangential directions. The use of a desiccant in compositions based on used vegetable oil and starch makes it possible to reduce the drying time and solidification of the surface film and improve the water-repellent properties of wood. The optimal dosages of the siccative and filler were selected. A comparative assessment of the use of compositions based on used vegetable oil fordifferent types of wood is carried out on theexample of birch and pine. The developed impregnating compositions have availability, low cost and environmental safety. The use of protective compositions based on used vegetable oil allows you to improve the properties of natural wood and dispose of production waste.