Two-step analytical procedure for the characterization and quantification of metal soaps and resinates in paint samples

Nasa, Jacopo La; Lluveras‐Tenorio, Anna; Modugno, Francesca; Bonaduce, Ilaria

doi:10.1186/s40494-018-0222-1

Cited by 11 publications

(3 citation statements)

References 35 publications

(42 reference statements)

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“…It is important to underline that the differences in behaviour observed among the paint from the different suppliers can be ascribed not only to the different composition of the lipid binders highlighted by HPLC-MS analysis, but can also partly derive from the influence of other components of the formulation, as additives, or a different composition of the CdS pigment. The influence of paint additives on ageing and curing of modern oil paint has been studied in the course of the CMOP project 14,36 and is beyond the scope of the present investigation.…”

Section: Resultsmentioning

confidence: 99%

On the influence of relative humidity on the oxidation and hydrolysis of fresh and aged oil paints

Modugno

Gianvincenzo

Degano

et al. 2019

Sci Rep

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Modern oil paintings are affected by conservation issues related to the oil paint formulations and to the fact that they are often unvarnished, and in direct contact with the environment. Understanding the evolution of the molecular composition of modern oil paint during ageing, under the influence of environmental factors, is fundamental for a better knowledge of degradation phenomena and risk factors affecting modern art. We investigated for the first time the influence of relative humidity on the chemical composition of modern oil paints during curing and artificial ageing. For this purpose, modern oil paint layers naturally aged for 10 years were further artificially aged in low and high relative humidity conditions. Moreover, the influence of RH% on the curing of fresh paint layers was studied. The paints used in the experiments are from three suppliers (Old Holland, Winsor&Newton, and Talens), and contain cadmium or cadmium zinc sulfide as main pigment. The changes in the composition of extracts of paint samples were investigated by direct electrospray mass spectrometry with a quadrupole-time of flight mass analyser (ESI-Q-ToF). The obtained mass spectral data were interpreted by means of principal component analysis (PCA) operated on a data set containing the relative abundance of ions associated to significant molecules present in the extracts, and also by calculating the ratios between the signals relative to fatty acids, dicarboxylic acids and acylglycerols, related to hydrolysis and oxidation phenomena. The same paint samples were also analysed, in bulk, by pyrolysis gas chromatography mass spectrometry (Py-GC/MS), achieving chemical information on the total lipid fraction. High performance liquid chromatography (HPLC) ESI-Q-ToF was carried out for the characterisation of the profile of free fatty acids (FFA) and acylglycerols, defining the nature of the oils used in the paint formulations, and for the determination of the degree of hydrolysis. This study demonstrated that relative humidity conditions significantly influence the chemical composition of the paints. Ageing under high RH% conditions produced an increase of the formation of dicarboxylic acids compared to ageing under low RH%, for all paints, in addition to a higher degree of hydrolysis, followed by evaporation of free fatty acids.

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Section: Resultsmentioning

confidence: 99%

On the influence of relative humidity on the oxidation and hydrolysis of fresh and aged oil paints

Modugno

Gianvincenzo

Degano

et al. 2019

Sci Rep

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“…Fragments from the samples were extracted and derivatized by two different trimethylsilyl derivatization reagents: 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) where HMDS induces silylation of free fatty acids present in the oil binding medium. BSTFA, on the other hand, will silylate all fatty acids present in the sample including free fatty acids and metal carboxylates [27][28][29][30]. The use of these two derivatization agents can qualitatively determine the metal carboxylate and the free fatty acid content in the ground samples.…”

Section: Gc-msmentioning

confidence: 99%

The influence of commercial primed canvases in the manifestation of metal soaps protrusions in Georgia O’Keeffe’s oil paintings

2020

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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.

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“…The extractable acyl glycerides (monoglyceride, diglycerides, and triglycerides) and their relative oxidation products together with the free fatty acids, were characterised and semi-quantified in a single chromatographic run. The soluble fraction was further characterised using a new GC-MS two-step analytical approach based on the selective derivatization of free fatty and dicarboxylic acids, and the metal carboxylates of free fatty and dicarboxylic acids, achieved via derivatisation with N,O-bis(trimethylsilyl)acetamide (BSTFA) and hexamethyldisilazane (HMDS) 21,22 . This new approach enabled the quantification of free metal soaps and free dicarboxylic acids within the soluble fraction, which was compared and combined with the results obtained using HPLC-ESI-Q-ToF.…”

Section: Introductionmentioning

confidence: 99%

The role of the polymeric network in the water sensitivity of modern oil paints

Nasa

Lee

Degano

et al. 2019

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Spectroscopic and mass spectrometric analytical techniques were used to characterise two naturally aged Winsor & Newton (W&N) Winsor Green (phthalocyanine green, PG7) artists’ oil colour paint swatches dating to 1993 and 2003. Infrared and Energy Dispersive X-ray (EDX) analysis indicated that the swatches were of closely similar composition, yet the swatch from 2003 was water-sensitive whilst the swatch from 1993 was not. Water-sensitivity is a conservation challenge associated with significant numbers of modern oil paintings and this study aimed to further develop our understanding of the molecular causes of water sensitivity. SEM elemental mapping of samples taken from both swatches provided no indication for the formation of epsomite – a known cause of water sensitivity in some modern oil paintings. Liquid chromatography coupled with mass spectrometry (HPLC-MS) and gas chromatography coupled with mass spectrometry (GC-MS) also revealed very similar qualitative-quantitative composition in terms of unbound and esterified medium fractions. The polymeric network was investigated using analytical pyrolysis. A combination of flash pyrolysis coupled with gas chromatography mass spectrometry (Py-GC-MS) together with evolved gas analysis mass spectrometry (EGA-MS) revealed that the polymeric material was relatively more abundant in the non-water-sensitive paint. This is the first multi-analytical study that has demonstrated a correlation between water-sensitivity and the degree of polymerisation of the oil medium; independent of other known causes of water-sensitivity.

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Two-step analytical procedure for the characterization and quantification of metal soaps and resinates in paint samples

Cited by 11 publications

References 35 publications

On the influence of relative humidity on the oxidation and hydrolysis of fresh and aged oil paints

On the influence of relative humidity on the oxidation and hydrolysis of fresh and aged oil paints

The influence of commercial primed canvases in the manifestation of metal soaps protrusions in Georgia O’Keeffe’s oil paintings

The role of the polymeric network in the water sensitivity of modern oil paints

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