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In attempting to document the degradation processes occurring on cultural heritage objects, imaging-based analytical techniques present many advantages, as they provide spatial and spectral information and allow the simultaneous investigation of the chemical and morphological characteristics of a sample. This study presents a protocol based on chemical imaging – Fourier transform infrared microspectroscopy (μ-FTIR) and hyperspectral imaging (HSI) – aimed at monitoring the formation of metal soaps on model metal coupons. Oil-painted metal supports are in fact not immune to degradation due to metal soaps formation, a phenomenon that affects all oil-painted surfaces from the initial curing of the paint film. Copper and zinc sheets were coated with cold-pressed linseed oil and artificially aged for one month in order to instigate the formation of metal soaps. Their reaction was then monitored by means of µ-FTIR. The chemical maps showed an increasing trend over time, elucidating some aspects and differences in the mechanism of formation of the organic salts for the two metal substrates. Additionally, the samples were analysed using two hyperspectral cameras, operating in the visible-near infrared and short-wave infrared spectral range. The appropriateness of the two cameras in the investigation of metal soaps, and the effect of the thickness of the coating on the data obtained, is discussed here.

Up to 70 % of the oil paintings conserved in collections present metal soaps, which result from the chemical reaction between metal ions present in the painted layers and free fatty acids from the lipidic binders. In recent decades, conservators and conservation scientists have been systematically identifying various and frequent conservation problems that can be linked to the formation of metal soaps. It is also increasingly recognized that metal soap formation may not compromise the integrity of paint so there is a need for careful assessment of the implications of metal soaps for conservation. This review aims to critically assess scientific literature related to commonly adopted analytical techniques for the analysis of metal soaps in oil paintings. A comparison of different analytical methods is provided, highlighting advantages associated with each, as well as limitations identified through the analysis of reference materials and applications to the analysis of samples from historical paintings., Conservation and Heritage scientists frequently face challenging issues related to metal soaps phenomena in oil paint systems. This review provides a critical overview of analytical techniques available for the identification, localisation and study of the presence of metal soaps. Advantages and disadvantages of each technique are discussed and the comparison between data collected from ad hoc and real painting samples is reported.

In this study, the investigation of the oil painting on canvas I Tesori del Mare made by Plinio Nomellini in 1901 is presented. The aim of the research was threefold: the examination of the state of conservation in view of the restoration treatment, together with the identification of the causes of degradation and the study of the artistic technique. During the years, the artwork underwent several cleaning and fixing interventions, resulting in a patchy appearance of the surface. Nevertheless, the presence of consistent liftings persists, while the protective coating shows uneven chromatic alteration, both requiring further analysis. Multispectral imaging allowed for better visualization of the figuration’s structure and the restored areas. The combined use of Raman spectroscopy, Fourier Transform Infrared spectroscopy in the Attenuated Total Reflection mode (FT-IR ATR), and Scanning Electron Microscopy coupled with an Energy Dispersive Spectroscopy (SEM/EDS) enabled better understanding of the stratigraphy through the identification of some pigments, the binder, and the aged varnish layer on the top. SEM/EDS highlighted the presence of zinc in both the ground layer and the paint layers. Furthermore, FT-IR ATR spectroscopy showed peaks related to metal soaps such as zinc stearate, which are known to cause severe delamination of the paint layers, explaining the recurring lifting issues. Eventually, the varnish layer was found to be acrylic resin, presumably mixed with varnishes applied in past restoration treatments.

This article presents an overview of Liu Kang’s (1911–2004) canvas painting supports from his early artistic phases, Paris (1929–1932) and Shanghai (1932–1937). The research was conducted on 55 artworks from the collections of the National Gallery Singapore and Liu family. The technical examination of the paintings was supplemented with archival photographs of the artist at work to elucidate his practice of preparation of painting supports. The analyses conducted with light microscopy, SEM–EDS, and FTIR allowed us to characterise the structure of the canvases and identify the natural fibres and formulation of the grounds. In addition, references to contemporary colourmen catalogues, in relation to certain materials, were made. The obtained results suggest that, in both locations, Liu Kang employed commercially prepared canvases purchased by the roll or by the metre, together with bare strainers or stretchers of standard sizes. In Paris, the artist commonly used linen canvases, while in Shanghai he preferred cotton canvases, with linen used sporadically. The identified grounds from the Paris and Shanghai canvases are white and single-layered, but their formulations vary significantly between the two locations. Hence, grounds composed predominantly of lead white with extenders and drying oil as a binder are considered as exclusive to the Paris phase. However, semi-absorbent or absorbent grounds based on chalk are typical for Shanghai phase. This research contributes to the knowledge of Liu Kang’s painting materials and working practices during the pre-war period in Paris and Shanghai.

Organic remains preserved on eight copper alloy artifacts of the Byzantine Collection of the Benaki Museum with an Egyptian provenance were investigated, implementing a multi-analytical approach combining microscopy-FTIR and GC/MS. The transmission spectra of powder samples provided important information on the vessels regarding inorganic and organic components. In the latter case, subsequent extractions with a range of solvents allowed discrimination of components with different polarities and provided data on the suitability of the solvents for the acquisition of more informative spectra. GC/MS was implemented for the detailed characterization of the compounds present in the samples because of the complex nature of the residues preserved. A wide range of fatty acid oxidation products was identified, including a series of α, ω-dicarboxylic acids typical of such remains. In addition, vicinal dihydroxy-docosanoic and dihydroxy-eicosanoic acid, oxidation products of erucic and gondoic acid, respectively, were detected. Both are found in abundance in oils from plants belonging to the Brassicaceae family and imply their multiple uses in medieval Egypt.

In a cultural heritage context, fatty acids are usually found as breakdown products of lipid-containing organic remains in archaeological findings, binders in aged oil paintings, and additives in modern art-related materials. They may further interact with the ionic environment transforming into metal soaps, a process that has been recognized as a threat in aged paintings but has received less attention in archaeological objects. The investigation of the above related categories of materials with infrared spectroscopy can provide an overall picture of the organic components’ identity and demonstrate their condition and prehistory. The capability of investigating and distinguishing fatty acids and their metal soaps through their rich infrared features, such as the acidic carbonyl, the carboxylate shifts, the variable splits of alkyl chain stretching, bending, twisting, wagging, and rocking vibrations, as well as the hydroxyl peak envelopes and acid dimer bands, allows for their direct detailed characterization. This paper reviews the infrared spectra of selected saturated fatty monoacids and diacids, and their corresponding sodium, calcium, and zinc salts and, supported by newly recorded data, highlights the significance of their spectroscopic features.

In this study, the structural characteristics and thermal degradation behaviour of barium, calcium and zinc soaps of hemp seed oil prepared using the metathesis method are reported. Scanning electron micrographs of the metal soaps showed similar plate-like microstructures and are indicative of an orderly packed particulate structure. The bands at 1509, 1539 and 1543 cm-1 in the FTIR spectra showed the association of the carboxylate ion with Ba, Ca and Zn ions respectively The thermal decomposition consisted of one single step on the weight loss – temperature curves located around 250 – 450 oC for all the divalent metal soaps at the various heating rates and the observed loss in weight which occurred before 200 oC was minimal (< 10%). The average values of the apparent activation energy for the thermal process were 18.73, 13.77 and 8.48 kJ/mol for Zn-HSO, Ca-HSO and Ba-HSO respectively.

Metal soaps formation is a well-known issue in oil paintings. Along the lifetime of the painting, carboxylic acids coming from drying oil (free fatty acids, acids from hydrolysis of triglycerides and from oxidation processes) can react with cations of some pigments (in particular, smalt, lead white and zinc white) forming the related carboxylic salts. As observed by many authors, the formation of these carboxylates, with the tendency to migrate and to aggregate, not only modifies the behavior and the aspect of the paint film but also complicates the cleaning approach. In previous works we have demonstrated that a similar pigment reactivity is possible even in presence of natural resins (such as colophony, dammar, mastic, etc) historically used as final varnishes on paintings. In this case, in the reactions the terpenic acids, among the main components of the resins, are involved. In this work, the carboxylates formation kinetics has been studied starting from two representative acids (palmitic and abietic) of painting oils and natural varnishes. Successively, the reactivity of the palmitic acid with the potassium abietate and of the abietic acid with the potassium palmitate has been verified. This investigation aims at clarifying in which way terpenic acids can be involved in the metal soaps reactivity confirming that also surface varnishes may play a significant role in the carboxylates formation and reactivity. It is important to keep in mind that a finishing varnish can be removed and reapplied many times during the lifetime of a painting, thus renewing the provision of reactive terpenic acids at the interface of the painted layers.

Metal soaps are formed in paint layers thorough the reaction of metal ions of pigments and fatty acids of organic binders. In this study, micro-ATR-FTIR spectroscopic imaging was used to analyse the formation of lead soaps in oil-based paint layers in relation to their exposure to moisture sources. The investigations were carried out on authentic samples of complex stratigraphies from cold painted terracotta statues (Sacred Mount, Varallo, UNESCO) and different IR-active lead white pigments, organic materials, and lead soaps were discriminated. The saponification of selected paint layers was correlated to the conservation history, the manufacturing technique, and the build-up of layers. The presence of hydrophilic layers within the stratigraphy and their role as a further water source are discussed. Furthermore, the modifications experienced by lead-based pigments from the core of an intact grain of pigment towards the newly formed decay phases were investigated via a novel approach based on shift of the peak for the corresponding spectral bands and their integrated absorbance in the ATR-FTIR spectra. Qualitative information on the spatial distribution from the chemical images was combined with quantitative information on the peak shift to evaluate the different manufacture (lead carbonate, basic lead carbonate) or the extent of decay undergone by the lead-based pigments as a function of their grain size, contiguous layers, and moisture source. Similar results, having a high impact on heritage science and analytical chemistry, allow developing up-to-date conservation strategies by connecting an advanced knowledge of the materials to the social and conservation history of artefacts. Supplementary Information The online version of this article (10.1007/s00216-020-03016-6) contains supplementary material, which is available to authorized users.

Metal soaps or metal alkanoates are metal-organic complexes held together with metal cations and the functional groups of hydrocarbon chains. They can be synthesized at a high yield by simply mixing the metal and organic sources, forming crystalline frameworks with diverse topology, and have been studied in the past because of their rich polymorphism-like liquid crystals. Their ability to melt while retaining the crystalline properties upon cooling is unique among nanoporous materials and is especially attractive for membrane fabrication. Herein, metal soaps as a new class of material for molecular separation are reported. Three metal soaps, Ca(SO4C12H25)(2), Zn(COOC6H13)(2), and Cu(COOC9H19)(2), hosting lamellar structure with molecular-sized channels are synthesized. They are processed in thin, intergrown, polycrystalline films on porous substrates by two scalable methods, interfacial crystallization and melting with an extremely small processing time (a minute to an hour). The resulting crystalline films are oriented with the alkyl chains perpendicular to the porous substrate which favors molecular transport. The prepared membranes demonstrate attractive gas separation behavior, e.g., 300-nm-thick Ca(SO4C12H25)(2)membrane prepared in a minute using interfacial crystallization yields H(2)permeance of 6.1 x 10(-7)mol m(-2)s(-1)Pa(-1)with H-2/CO(2)selectivity of 10.5.

During a routine condition survey in 2007 at the Georgia O’Keeffe Museum in Santa Fe, micro-protrusions were found scattered across the surfaces of the artist’s oil paintings produced between 1920 and 1950. In many of her works, including Pedernal (1941) and A Man from the Desert (1941), lead soaps were found aggregated at the painting surface, forcing the surrounding paint to deform into pin-sized protrusions. The structure and composition of the protrusions was analyzed to determine why they formed. Microsamples were removed from four of O’Keeffe’s paintings and investigated using a combination of SEM–EDX, GC–MS, and FT-IR. The combined GC–MS and FT-IR results indicate that the protrusions contain primarily lead carboxylates. The results obtained for a series of ground samples removed from four different paintings were then compared with samples collected from a commercially pre-primed canvas roll found in the artist’s house in Ghost Ranch, NM. We identified two different types of canvases: i) a commercially pre-primed canvas and ii) artist primed canvas. This commercially pre-primed canvas roll has a similar morphology to the ground layers in her paintings that contain protrusions additionally these grounds were found to contain an excess of free fatty acids and metal carboxylates (lead soaps) based on a comparison to canvases the artist primed herself. Based on the analytical results from the four paintings and the commercial pre-primed canvas, we concluded that the artist’s use of this particular commercially pre-primed canvas between 1920 and 1950 play an important role in the observed micro-protrusions.

Green pigments in micro-samples taken from three late-medieval painted objects from Norwegian churches have been investigated with the aim to characterize their constituents and understand how they relate to damages observed in passages containing green paints. The cross-sections were analyzed by optical microscopy under visible and UV light, Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectrometry and vibrational spectroscopies (Raman, ATR-FTIR). In addition, Gas Chromatography coupled with Mass Spectrometry was employed for the characterization of binding media, using a derivatization methodology recently developed for the detection of metal soaps in paint samples. This extensive characterization aided the identification of the individual constituents and the stratigraphy of green paints. It also builds the foundation for future ageing studies that can provide better insights into the mechanisms of the processes at stake in selective delamination of paints containing copper complexes.

Metal soaps and resinates are known to be spontaneously formed in artistic paintings, as a product of the reaction between aliphatic and terpenoid acids released by hydrolysis and oxidation of the organic media and certain cations contained in some inorganic pigments. In this paper we present an optimization and the validation of a GC/MS method for the qualitative and quantitative analysis of mixtures of terpenoid acids and aliphatic mono and dicarboxylic acids and metal carboxylates of terpenoid and aliphatic mono and dicarboxylic acids in the same paint microsample. This is based on a two-step analytical approach entailing the subsequent use of two silylating agents, N,O-bis(trimethylsilyl)trifluoroacetamide for the analysis of free acids and metal carboxylates, and 1,1,1,3,3,3-hexamethyldisilazane for the analysis of free acids. The application of this approach is possible because of the good stability at room temperature of the TMS derivatives of aliphatic and terpenoid species, characterized by high boiling points and relatively low vapour pressures. The method was then applied to the characterization of samples collected from two reference paint layers aged for 20 years, a paint sample taken from a pulpit, and sample of the varnish coating of a wooden writing desk, both from the second half of the seventeenth century.

In this paper we present a new analytical GC/MS method for the analysis of mixtures of free fatty acids and metal soaps in paint samples. This approach is based on the use of two different silylating agents: N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS). Our experimentation demonstrated that HMDS does not silylate fatty acid carboxylates, so it can be used for the selective derivatization and GC/MS quantitative analysis of free fatty acids. On the other hand BSTFA is able to silylate both free fatty acids and fatty acids carboxylates. The reaction conditions for the derivatization of carboxylates with BSTFA were thus optimized with a full factorial 32 experimental design using lead stearate and lead palmitate as model systems. The analytical method was validated following the ICH guidelines. The method allows the qualitative and quantitative analysis of fatty acid carboxylates of sodium, calcium, magnesium, aluminium, manganese, cobalt, copper, zinc, cadmium, and lead and of lead azelate. In order to exploit the performances of the new analytical method, samples collected from two reference paint layers, from a gilded 16th century marble sculpture, and from a paint tube belonging to the atelier of Edvard Munch, used in the last period of his life (1916–1944), were characterized.

International audience; This study focuses on the short-term reactivity of zinc oxide with different types of drying oils. Chemical grade zinc oxide (with diameter

The formation and growth of metal soaps is of interest in heritage science, as soaps have been linked to a range of alteration and degradation phenomena potentially affecting works of art. However, current approaches detect metal soaps mainly in an invasive way or only at a late formation stage when the metal soaps are formed on the surface of the artwork. In contrast, Optical Coherence Tomography (OCT) has been proven to be a very suitable tool to obtain subsurface morphological information of complex multi-layered systems, such as paintings, in a non-invasive way. In this work, the capability of detecting metal soaps with an 810 nm ultra-high resolution (UHR) OCT in a selection of real and mock-up samples has been explored with OCT virtual cross-section images complemented with invasive structural and chemical analysis (SEMEDX and ATR-FTIR spectroscopy and imaging). Although the visualization of metal soaps with OCT was evident in some samples, we also show that this is not always the case. In addition, the results of this work show that extra care is needed when interpreting OCT cross-section images to avoid the risk of misinterpreting features present in the paint stratigraphy.

The degradation process involving the formation of metal soaps in drying oils is a well-known problem due to the reaction of cations coming from pigments reacting with free fatty acids from the oil. A similar behavior has been observed during an experiment concerning the aging of different natural resins (shellac, dammar, and colophony) in the presence of common historic pigments (smalt, ochre, umber, azurite, lead white, zinc white, and titanium white). In the case of natural resins, the terpenic acids react with the cations in the pigments. Each resin shows a different reactivity and affinity to different cations related to the complex mixture of terpenic structures and acids contained in natural resins. So far it has not been possible to identify one or more specific acids preferentially involved in this “saponification” process. Colophony seems to be the most reactive resin, while zinc white and smalt appear to be the most reactive pigments. The explanation for the different reactivity of the acid components of the three resins is unclear. Studies on acidity of different resins, free acid mobility, and pigment reactivity are ongoing. Generally, the presence of a pigment has been proven to modify the stability of resins that have undergone accelerated aging. Mixtures of resins and pigments have been exposed to natural and different artificial aging conditions (photooxidative, thermal, thermo-oxidative, and wet cycles).

The degradation process involving the formation of metal soaps in drying oils is a well-known problem due to cations from pigments reacting with free fatty acids from the oil. The aggregation of these carboxylates in semi-crystalline structures can lead to eruptions through the paint layers and 'blooming' on the surface. In this work, the metal soaps formation in presence of natural resins has been assessed and studied by means of Fourier transform infrared spectroscopy with experiments concerning the ageing of drying oil and different natural resins (shellac, dammar and colophony) in the presence of common historic pigments (smalt, ochre, umber, azurite, lead white, zinc white and titanium white). Mixtures of resins and pigments have been exposed to photo-ageing in solar box up to 1000h, thermal ageing at 50°C up to 1100h and 6month of room conditions exposure as reference. The decrease in the intensity of the carbonyl band in the spectra, as well as the contemporary increase of the metal carboxylates (in the range from 1500 to 1650cm-1) absorption bands, were used as the main indicators of metal soap formation. It has been observed that some pigments, particularly zinc white and smalt, present a 'catalytic' effect favouring the simultaneous formation of associated oxalates. The formation of oxalates and different degradation products from natural resins in the presence of pigments is particularly important, as it deeply affects the removability of varnishes and, more generally, the cleaning processes. Moreover, it permanently modifies the interface between painting and varnish layers as well as the aesthetic aspects of the painted surfaces. The influence of natural resins reactivity with pigments and their role in the oxalate formation is an issue still unexplored.

The interaction of sodium octanoate, decanoate or dodecanoate with lead(II) has been studied in aqueous solutions using potentiometry, electrical conductivity, turbidity and ICP–OES measurements. These show an alkyl chain length dependence on the behavior. At the lead(II) concentration used (1.0 mM), relatively strong interactions are observed with the decanoate and dodecanaote, leading to formation of the lead carboxylates (soaps) as insoluble complexes. All techniques show 1:2 (metal:carboxylate) stoichiometry corresponding to charge neutralization. With sodium octanoate and lead(II), a rather weaker interaction is seen, and complexation is only observed at metal:carboxylate ratios > 0.5. However, in contrast to our previous work on octanoate and calcium(II) in aqueous solutions [1] , precipitation does occur at higher concentrations. This difference between the behavior of the metal ions is probably due to the more covalent nature of the bonds of the carboxylate with Pb2+ than with Ca2+. Association constants of the complexes have been determined from potentiometric measurements and are consistent with data on solubility products. A comparison is made of the effect of surfactant head group on the interactions with lead(II) using two surfactants with the same chain length: dodecanoate and dodecylsulfate. Differences in their interactions with this metal ion in aqueous solutions are interpreted in terms of greater covalency of the bond between the metal and the carboxylate than with the sulfate group.

The origin(s) and role(s) of metal soaps in paints are a worldwide concern today. These hybrid compounds, containing both fatty acid chains and metals associated with a carboxylate function, are increasingly identified in paints. As reviewed in the first part of this work, the presence of metal soaps in paints is differently interpreted in scientific publications: metal soaps are sometimes considered to play a positive role as anchor points, during paint drying processes; they can also be considered as responsible for many degradation processes (protrusions, efflorescences, darkening, etc.). Their origins are also interpreted in various ways. In some paintings (in particular from the twentieth century), they have sometimes introduced on purpose, as additives, to modify the physical properties of the painting materials. In older paintings, metal soaps are usually thought to result from an uncontrolled reaction of oil with lead-based pigments, in particular lead white, red lead, and lead tin yellow. In the second part of this work, the review of historical recipes of lead-based paint shows an important number of recipes based on controlled mixing of oil with lead driers. In the third part, the experimental reproduction of such traditional recipes using walnut oil and litharge (PbO) shows that lead soaps can be formed, both in about one hour at ∼100°C, or in about one month at room temperature. It shows as well that after a few years, litharge is no longer detected in the paint medium, while different lead carbonates are. Finally, the micro-infrared spectroscopy and micro-X-ray diffraction re-analysis of protrusions from a nine-year model painting shows together with lead soaps, the presence of Pb5(CO3)3(OH)2O (‘synthetic plumbonacrite’), an unusual phase recently observed in a protrusion from a painting by Vincent Van Gogh. This work highlights (i) the multiple origins and roles of metal soaps in paints and (ii) the importance of combining the analysis of fragments from historical paintings with the analysis and reproduction of historical recipes. In particular, we show that the components detected today in historical paintings may severely differ from those originally used or prepared by the painter, complicating the assessment of the painter's intentions. More than the presence of metal soaps, the key questions to be tackled should be about their origins and (re)mobilization.

Zinc soaps of rubber seed oil (RSO) and epoxidised rubber seed oil (ERSO) were prepared and their use as PVC stabilizers investigated. Characterization of Zn soaps of RSO prepared by different techniques and ERSO gave information on the purity, structure and thermal behaviour of these materials. From the analysis, the production of these materials for use in thermal stabilization of PVC would be optimized as their use greatly enhanced the stability of PVC as obtained from the conductivity measurements using the 763 PVC Thermomat. The minimum amount of HCl release was obtained for the samples with Zn soaps and ERSO indicating a synergistic effect. Zn soaps having Zn(OH)2 stabilized PVC better than pure Zn soaps., Turkish State Planning Organization Project 2002, K120 390

This study investigated the extraction of Cocos nucifera seed oil (CSO) from Cocos nucifera seed using aqueous processing and the production of metal soaps from the oil and their characterization in terms of colour, pH, free caustic alkalinity, foaming power, foam stability, and corrosion inhibition test. The metal soaps of the oil produced by metathesis were soaps of nickel, calcium, barium, zinc, iron and magnesium. The results of tests of the metal soaps showed that Ni-CSO was greenish in colour, Zn-CSO, Mg-CSO, Ba-CSO and Ca-CSO were white and Fe-CSO had a dark-brown colour. The pH of the metal soaps varied between 6.5 to 8.2. The free caustic alkalinity was low and varied between 0.30 % to 0.43 %. Foam stability was in the order Fe-CSO 0.80, Ca-CSO 0.81, Zn-CSO 0.86, Ni-CSO 0.90, Mg-CSO 0.92 and Ba-CSO 0.93. For corrosion inhibition test Ni-CSO at 100 mg/L, Ca-CSO at 60 mg/L, Mg-CSO, Ba-CSO and Fe-CSO at 40 mg/L inhibited tiger head razor blade corrosion while the other concentrations of the metal soaps showed varied degrees of corrosion.Keywords: Cocos nucifera seed oil; metal soaps; corrosion inhibition; foam stability

Mesophase induction was observed in binary mixtures of the liquid-crystalline lanthanum(III) dodecanoate and a nonmesomorphic lanthanide(III) dodecanoate. The compounds have the stoichiometry La(x)Ln(1-x)(C11H23COO)3 (where x is the mole fraction of lanthanum, Ln = Nd, Eu, Ho, Tb, and Yb) and were characterized by elemental microanalysis. The thermal behavior was investigated by hot-stage polarized optical microscopy, by differential scanning calorimetry, and by X-ray diffraction at elevated temperatures. The mesophase behavior of the compounds strongly depends on the composition of the mixtures and on the lanthanide ion. For lanthanum-europium dodecanoate mixtures, less than 4 mol % lanthanum(III) dodecanoate is needed to induce mesomorphism, whereas for lanthanum-ytterbium mixtures, the minimum amount of lanthanum(III) dodecanoate increases to 48 mol %. ispartof: Chemistry of materials vol:13 issue:7 pages:2243-2246 status: published

Lorsque l’oxyde de zinc est le composant principal d’une préparation à l’huile, sa rigidité et son comportement fragile pourrait affecter le système de peinture tout en produisant des dommages aux couches supérieures pigmentées. Des échantillons de blanc de zinc et blanc de plomb ont été préparés et vieillis artificiellement. Des données visuelles ont été recueillies et la spectroscopie IRTF s’est révélée efficace pour confirmer la formation de carboxylates de zinc. Des lignes directrices pour les traitements de conservation ont été établies en ce qui concerne les procédures techniques et le choix des matériaux. When zinc oxide is the main constituent of a ground layer, its stiffness and brittle behavior could affect the whole paint system, producing damages to upper pigmented layers. Zinc white and white lead paint samples have been prepared and artificially aged. Visual data have been collected, and FTIR spectroscopy has proved effective in confirming the formation of zinc carboxylates. Guidelines for conservation treatments were drawn on both technical procedures and choice of materials.

The interaction of pigments and binding media may result in the production of metal soaps on the surface of paintings which modifies their visible appearance and state of conservation. To characterise more fully the metal soaps found on paintings, several historically accurate oil and egg yolk tempera paint reconstructions made with different pigments and naturally aged for 10 years were submitted to attenuated total reflectance Fourier transform infrared (ATR FTIR) microspectroscopic analyses. Standard metal palmitates were synthesised and their ATR spectra recorded in order to help the identification of metal soaps. Among the different lead-based pigments, red lead and litharge seemed to produce a larger amount of carboxylates compared with lead white, Naples yellow and lead tin yellow paints. Oil and egg tempera litharge and red lead paints appeared to be degraded into lead carbonate, a phenomenon which has been observed for the first time. The formation of metal soaps was confirmed on both oil and egg tempera paints based on zinc, manganese and copper and in particular on azurite paints. ATR mapping analyses showed how the areas where copper carboxylates were present coincided with those in which azurite was converted into malachite. Furthermore, the key role played by manganese in the production of metals soaps on burnt and raw sienna and burnt and raw umber paints has been observed for the first time. The formation of copper, lead, manganese, cadmium and zinc metal soaps was also identified on egg tempera paint reconstructions even though, in this case, the overlapping of the spectral region of the amide II band with that of metal carboxylates made their identification difficult.

Lanthanide(III) hexanoate 1,10-phenanthroline complexes crystallise in the space group P2(1)/n. The compounds consist of dimers, whereby two lanthanide ions are held together by two bidentate bridging and two tridentate bridging carboxylate groups. The first coordination sphere of the lanthanide ions is completed by one bidentate chelating carboxylate group and by one bidentate 1,10-phenanthroline molecule, resulting in the coordination number 9. The dimers have a spherical form, which has important consequences for the thermal properties of complexes. The basic idea behind the preparation of this type of compounds is the stabilisation of the ionic lanthanide layer, so that the smaller lanthanide ions (from which the normal alkanoates do not show mesomorph-ism because they are too small) show liquid crystallinity. The stabilisation of the ionic layer was successful, expressed by the high melting temperatures, but mesomorphism is not observed. The absence of mesomorphism is related to the isotropic structure of the compounds. A lower symmetry is obtained when a hexanoate group is replaced by a nitrate group. Thulium(III) dihexanoate nitrate 1, 10-phenanthroline crystallises in the space group P (1) over bar. However, this compound also shows a spherical dimeric structure, but no mesomorphism. ispartof: Zeitschrift für Anorganische und Allgemeine Chemie vol:629 issue:6 pages:975-980 status: published

Paints and other coating systems form a solid layer during the film-forming process where different physical and chemical processes are important.Oxidative drying is a process in which the evaporation of solvents is followed by an oxidation process of the unsaturated binder under influence of oxygen in the air. This oxidative drying process is accelerated by the addition of catalysts, referred to as driers.

The formation of metal soaps (metal complexes of saturated fatty acids) is a serious problem affecting the appearance and structural integrity of many oil paintings. Tailored model systems for aged oil paint and time‐dependent attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy were used to study the diffusion of palmitic acid and subsequent metal soap crystallization. The simultaneous presence of free saturated fatty acids and polymer‐bound metal carboxylates leads to rapid metal soap crystallization, following a complex mechanism that involves both acid and metal diffusion. Solvent flow, water, and pigments all enhance metal soap crystallization in the model systems. These results contribute to the development of paint cleaning strategies, a better understanding of oil paint degradation, and highlight the potential of time‐dependent ATR‐FTIR spectroscopy for studying dynamic processes in polymer films.

Monoand dichloride soaps awl tri-soaps of aluminium have been synthesised by the interaction of anhydrous aluminium chloride and fatty acids in different stoiehiometric ratios in different organic solvents. All chloride maps and tri-soaps givemobile solutions of low viscosity in organic solvents.