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![Sample B1, mapping of the 548 cm −1 blue chromophore signal intensity across an area containing both blue and white (degraded) paint showing (a) the light microscopy image of the ultramarine sample surface, (b) the intensity distribution of the chromophore signal with red being high intensity and (c) comparison of two spectra, one taken from a blue area and one from a white. Spectra acquired using 10% laser power (P sample ~ 1.2 mW), 6 s exposure time, and one accumulation [Colour figure can be viewed at wileyonlinelibrary.com]](profile/Ester-Ferreira/publication/320171629/figure/fig4/AS:681719518748673@1539546007392/Sample-B1-mapping-of-the-548-cm-1-blue-chromophore-signal-intensity-across-an-area.png)
Sample B1, mapping of the 548 cm −1 blue chromophore signal intensity across an area containing both blue and white (degraded) paint showing (a) the light microscopy image of the ultramarine sample surface, (b) the intensity distribution of the chromophore signal with red being high intensity and (c) comparison of two spectra, one taken from a blue area and one from a white. Spectra acquired using 10% laser power (P sample ~ 1.2 mW), 6 s exposure time, and one accumulation [Colour figure can be viewed at wileyonlinelibrary.com]
Source publication
A specific case of degradation was observed in synthetic ultramarine paint within 3 paintings from the early 20th century, manifesting as an intricate pattern of white lines criss-crossing the blue paint surface. Raman spectroscopy can be performed directly on untreated sample surfaces and is sensitive to the colour components in ultramarine (S3⁻ a...
Contexts in source publication
Context 1
... intensity of the S 3 − chro- mophore peak at 548 cm −1 was mapped using the 785-nm laser, NA 0.50 objective, with 10% laser power (P sample ~ 1.2 mW), 6 s exposure time, and one accumula- tion. The mapped area was roughly 60 × 85 μm, and the results are shown in Figure 6. The map of chromophore signal intensity in Figure 6 shows a strong decrease in counts in areas, which are white compared to those, which have retained their blue colour. ...
Context 2
... mapped area was roughly 60 × 85 μm, and the results are shown in Figure 6. The map of chromophore signal intensity in Figure 6 shows a strong decrease in counts in areas, which are white compared to those, which have retained their blue colour. This is also evident when looking at individual spectra, where a clear decrease in the 548 cm −1 signal, corresponding to the blue S 3 − , can be observed in the spectra taken from the white region. ...
Citations
... In the world of art and art restoration, the deterioration of ultramarine blue is known as "ultramarine sickness" or "ultramarine disease" (9)(10)(11)(12)(13)(14). Different alternatives have been developed for the protection of UB pigment from degradation. ...
The paper analyses the degradation process of commercial ultramarine blue pigments in cementitious materials. For this purpose, two commercial pigments (with and without a protective coating) in different solutions and cement pastes are studied incrementally. The results show that pigment degradation occurs due to an ion exchange phenomenon; during hydration high ion contents are released, calcium and potassium being the most aggressive for the pigment. Calcium distorts the unit cell; between the sodium of the pigment and the potassium in the medium a cation exchange phenomenon takes place. Both processes lead to the diffusion of sulphate and sulphide ions from the pigment to the medium causing loss of colour and the formation of ettringite.
... Within studies of oil paint, Raman scattering has mostly been applied in microspectroscopy experiments where only one or several spatial points are analyzed (Chen-Wiegart et al. 2017;Higuchi et al. 1997;Keune et al. 2013;Mahon et al. 2020;Monico et al. 2011Monico et al. , 2013Monico et al. , 2014Otero et al. 2014;Spring and Grout 2002;Trentelman et al. 1996). In some studies, where resolving spatial distributions is of crucial importance, raster scans are performed (Cato et al. 2017;Lau et al. 2008;Monico et al. 2015bMonico et al. , 2020aRopret et al. 2010). This yields hyperspectral Raman spectroscopy maps with micrometric spatial resolution, from which specific features can be integrated to obtain chemically specific distribution images on the microscale. ...
... Monico et al. (2015bMonico et al. ( , 2020a show how this approach can be used to map out different types of chrome yellows and to detect poorly crystalline, hexagonal CdS and some of its degradation products. Cato et al. (2017) show how mapping a specific vibration of the blue S • 3 − radical anion chromophore over an ultramarine oil paint surface reveals a local decrease in the chromophore concentration in optically altered regions: implying that the oxidation of sulfur chromophores may have caused ultramarine discoloration. ...
Oil paint is a dynamic system that undergoes chemical alteration on several time and length scales. At the short term, curing reactions are necessary for oil to dry properly. At longer time scales, a wide variety of other chemical processes can negatively affect the visual appearance or mechanical properties of historical artistic paint systems. The development of chemical imaging methods capable of covering length scales continuously from the millimetric to micro- or even nanoscale is key in understanding the chemical composition of a painting and the historical changes thereof. Such imaging methods can help in assessing to which extent the original painting’s composition may have been modified by chemical degradation processes. Processes that occur in the highly heterogeneous mixtures of binders, pigments, additives, alteration products and possibly later repainting and restoration treatments. Establishing the precise biography of the painting contributes to evaluate its authenticity. New modalities and novel methods of microchemical imaging provide access to previously unexplored length scales, are capable of better differentiation between the various oil paint components (original composition or later addition), and allow performing faster analysis to produce higher definition images. In this review, we report on recent methodological developments and future prospects to determine oil paints composition using microchemical imaging at the micro- and nanoscale.KeywordsImagingSpectroscopyMicroscopyPaintPigments
... Within studies of oil paint, Raman scattering has mostly been applied in microspectroscopy experiments where only one or several spatial points are analyzed (Chen-Wiegart et al. 2017;Higuchi et al. 1997;Keune et al. 2013;Mahon et al. 2020;Monico et al. 2011Monico et al. , 2013Monico et al. , 2014Otero et al. 2014;Spring and Grout 2002;Trentelman et al. 1996). In some studies, where resolving spatial distributions is of crucial importance, raster scans are performed (Cato et al. 2017;Lau et al. 2008;Monico et al. 2015bMonico et al. , 2020aRopret et al. 2010). This yields hyperspectral Raman spectroscopy maps with micrometric spatial resolution, from which speci c features can be integrated to obtain chemically speci c distribution images on the microscale. ...
... Monico et al. (2015bMonico et al. ( , 2020a show how this approach can be used to map out different types of chrome yellows and to detect poorly crystalline, hexagonal CdS and some of its degradation products. Cato et al. (2017) show how mapping a speci c vibration of the blue S • 3 − radical anion chromophore over an ultramarine oil paint surface reveals a local decrease in the chromophore concentration in optically altered regions: implying that the oxidation of sulfur chromophores may have caused ultramarine discoloration. ...
... Ultramarine, depending on customer needs, comes in the following colour modifications: ultramarine blue, ultramarine green, ultramarine purple and ultramarine red, of which ultramarine blue has found the widest application in various industries [7,8,9,10,11,12]. ...
The article describes the features of ultramarine, its modifications, viz. ultramarine blue. The requirements for ultramarine blue grades are observed, the one-stage and two-stage technologies for the production of ultramarine blue are described, the advantages and disadvantages of both methods are listed, new recommendations for the production of ultramarine blue are offered.
... Finally, the μ-Raman spectroscopy identified the characteristic bands of chrome yellow at 843 cm −1 (CrO 4 2− stretching) and of ultramarine blue at 548 cm −1 (S 3 − stretching vibration) [21,30,62,67,71,[82][83][84], in mixture with vermillion (bands at 257 and 347 cm −1 ) and lead white (1051 cm −1 due to the stretching of CO 3 2− ) ( Fig. A6a) [30,45,[62][63][64][65]69,70]. Different blue and yellow pigments were identified in the analysis of green areas by XRF and μ-Raman because the analyses were performed in different zones of the paints. ...
The study and the characterisation of modern and contemporary oil paintings is still a challenging issue, in particular considering the significant changes in paint production across the 19th and 20th centuries.
This paper presents the results of the first physico-chemical integrated study of the artistic materials used in six paintings from the School of Art and Higher Design of Valencia (Escola d'Art i Superior de Disseny, EASD-Valencia), artworks created between 1871 and 1943 by four famous Valencian artists: Salustiano Asenso Arozarena, Salvador Abril I Blasco, Enrique Navas Escuriet and José Bellver Delmás.
A wide range of inorganic and organic compounds was identified through a multi-analytical approach by means of visible reflectance spectroscopy, XRF, μ-Raman, FTIR and GC–MS. The investigation on the binding media suggests the use of commercial paint formulations including mixtures of drying, slow- and non-drying oils and the presence of Gum Arabic as well. Traditional pigments (such as vermillion, earth pigments, lead white) and modern pigments (such as zinc white, cobalt and chromium-based pigments) were identified together with fillers and extenders. Degradation products, in particular zinc and lead soaps having strong conservation implications, were also detected.
This work, focusing on the identification of the palettes and the binding media used by the selected artists, aims at providing meaningful data and interesting case studies that are useful beyond the Valencian painters solely. This study provides new insight into the use of 19th–20th century commercial oil paints and the selection of painters' palette and their artistic production techniques. Besides, this work highlights the necessity of a multi-analytical approach to obtain valuable information for documentation and preventive conservation.
... The presence of pigments in cultural heritage is one of the things that has a creative expression in the artworks. Moreover, it contains valuable information about the evolution process of history and humanity. In the previous part of the review studies of pigments, white lead and red lead were investigated. In continuation of scientist studies, the present review provides comprehensive point of view in the field of traditional pigments, emerald green and ultramarine blue. In order to achieve this purpose, by collecting and reviewing the current knowledge of this field, researchers have evaluated pigments from some points of view including their structure, application, evolution throughout history, general pigment properties, preparation and synthesis methods. Furthermore, optical properties, particle characteristics and some chemical properties, identification methods and types of degradation in these pigments were examined. In this regard, this research tries to strengthen the process of scientific and technical investigation of historical pigments based on valid scientific data.
Modern and contemporary objects made of plastics are widely found in cultural heritage. Today, their preser- vation poses critical issues to conservators and scientists, as they can suffer from extensive degradation in a short time period. Color change (discoloration) is one of the alteration phenomena that can significantly affect their appearance. Discoloration is commonly associated with the degradation of polymers. However, pigments within plastics can also fade due to exposure to light. The identification of objects that contain light-sensitive pigments is demanding because of the sensitivity of plastics to color change. Normally sampling, extraction methods and destructive testing are required for the characterization of colorants in plastics. In this work, an innovative multi-analytical spectroscopic approach for the in situ identification of pigments in historical plastics was developed. Optical microscopy (MO), micro-energy dispersive X-ray fluo- rescence (μ-EDXRF), UV-Vis-NIR reflectance, photoluminescence (PL) and Raman microscopy (μ-Raman), were used for the analysis of artworks, industrial and daily objects dated from 1950s-2000s from Portuguese collections. A common colorists’ palette within the Portuguese plastics industry was identified: iron oxide (PR 101, α-Fe2O3), lead chromate molybdate (PR 104, Pb(Cr,Mo,S)O4), cadmium red (PR 108, Cd(S,Se); PR 113, (Cd,Hg)S) and cadmium yellow (PY 37, CdS; PY 35; (Cd,Zn)S) pigments, titanium whites (PW 6, TiO2 both rutile and anatase), bismuth oxychloride (PW 14, BiOCl) and organic β-naphthol lakes (PR 48, PR 49, PR 53). An exceptional pigment found was the pearlescent plumbonacrite pigment Pb5(CO3)3O(OH)2. In all the case studies, μ-Raman was the key analytical tool for pigment characterization in the plastic objects, providing conclusive data for their identification. The vibrational fingerprint of both inorganic and organic pigments was successfully recorded by focusing the laser beam on particle surfaces. The confocal microscopy system used in μ-Raman enabled the collection of spectral data from low concentrations of pigments (ap- proximately 0.1%-5%) on the micro-scale. In addition to pigments, information on the base polymer (mainly thermoplastics) and fillers was obtained. The analytical methods developed will facilitate the acquisition of complementary data from plastics allowing material identification and condition assessment in the future. This thesis focused on red pigmented plastic artifacts, as they were found to be severely faded among the studied objects. The identification of β-naphthol pigment lake PR 53 as a faded pigment highlighted its poor fastness in plastics, that together with the color change of PR 48 in plastic objects, reported in literature, suggests the particular susceptibility of β-naphthol red lakes to fading. PR 53, and the other β-naphthol reds, are historical pigments widely found in cultural heritage. However, little is known about their photodegradation and stability, especially when they are found in polymer media, and this knowledge is essential for their long- term preservation. For the first time, photodegradation quantum yields (ΦR) were calculated for a series of red pigments based on β-naphthol in order to quantify their photo-stability. ΦR values ranging from 3x10-6 to 4x10-5 were obtained, indicating relatively light-stable molecules. Bearing in mind that pigment fastness is not only related to the pigment itself, but also to its interaction with the confined environment, light-aging experiments (λ>300 nm) were conducted in solution, on powders, and in polymers to assess the role of the medium on the lightfastness of the pigments and their degradation pathways. A significant impact of the binder on their stability was found. Indeed, a higher sensitivity to light of PR 48 and PR 53 pigments, when incorporated in plastics than in powder, was observed. This new knowledge will contribute to the prediction of plastic fading and inform effective preventive conservation strategies for objects containing light- sensitive β-naphthol red pigments. Liquid- and gas-chromatography mass spectrometry (MS) were used for the characterization of the main degradation products. Extensive photodegradation was observed with the formation of phthalic compounds and phthalates in both solution and powder phases.
This review provides a general understanding of Raman spectroscopy for use in the identification of pigments and dyes. The methodologies associated with a number of different related applications are also summarized. The first part of this review clarifies our basic knowledge regarding natural minerals and pigments. The second part discusses the fundamentals of currently used Raman spectroscopy, including surface-enhanced Raman scattering, μ-Raman spectroscopy, Raman imaging and spatially offset Raman spectroscopy. The third part focuses on recent applications, including the identification and analysis of various pigments and dyes that are used in paintings and related artworks. These studies show that Raman spectroscopy has great potential for use as a method for the rapid, non-destructive identification of such substances.Graphical abstract
Light is a determining factor in the discoloration of plastics, and photodegradation processes can affect the molecular structures of both the polymer and colorants. Limited studies focused on the discoloration of heritage plastics in conservation science. This work investigated the discoloration of red historical polyethylene (PE) objects colored with PR 48:2 and PR 53:1. High-density and low-density PE reference polymers, neat pigment powders, and historical samples were assessed before and after accelerated photoaging. The applied methodology provided insight into the individual light-susceptibility of polyethylenes, organic pigment lakes, and their combined effect in the photoaging of historical plastic formulations. After light exposure, both PE references and historical samples yellowed, PR53:1 faded, and PR 48:2 darkened; however, both organic pigments faded severely in the historical samples. This highlights the role played by the plastic binder likely facilitating the pigment photofading. Fourier transform infrared spectroscopy and mass spectrometry techniques—EGA-MS, PY-GC/MS, and TD-GC/MS—were successfully employed for characterizing the plastic formulations and degradation. The identification of phthalic compounds in both aged β-naphthol powders opens new venues for studies on their degradation. This work’s approach and analytical methods in studying the discoloration of historical plastics are novel, proving their efficacy, reliability, and potentiality.
Among the artists’ materials of the nineteenth century, pastel crayons merit scientific interest since their early commercial formulations are mostly unknown and, until now, have been considerably less studied with respect to other contemporary painting materials. In this framework, research herein reports the results of a comprehensive multi-analytical study of 44 pastel crayons of two recognized brands (LeFranc and Dr. F. Schoenfeld) from the Munch museum collection of original materials belonging to Edvard Munch. The integrated use of complementary spectroscopic and hyphenated mass-spectrometry techniques allowed the compositional profiles of the crayons to be traced providing the identification of the inorganic and organic pigments, the fillers/extenders and the binders. All crayons resulted to be oil- based and the binder was identified to be a mixture of a drying oil (safflower or linseed oil), palm oil or Japan wax and beeswax. Among others, pigments such as ultramarine, chrome yellows, Prussian blue, manganese violet, viridian and madder lake have been identified. A significant alignment in formulations of the brands was observed with the only exception of the greens which showed distinctive pigment and filler compositions. The analytical information provided for these commercial artists’ materials will be of great interest for academia, museum and other institutions hosting art collections dating from the same period and it will be used by the Munch museum to draw proper conservation strategies of its own artwork collections.
