Modern Pigments Research Articles

Manuscript Illumination in 19th-century Italy. Material Analysis of Two Partial Copies from the Squarcialupi Codex

Abstract The illuminations in two Italian manuscripts are still a mystery today. Both manuscripts were based fully or partly on the Florentine Squarcialupi Codex (Florence, Biblioteca Medicea Laurenziana, Med. Pal. 87) dating from around 1410/15. With the help of a multi-analytical, non-destructive approach employing mobile instrumentation (XRF spectroscopy, visible reflectance spectroscopy and infrared reflectography), we examined the manuscripts Toronto, Thomas Fisher Rare Book Library, MSS 09700 and Düsseldorf, Kunstpalast, Inv. K 1925-67 for the first time with regard to their production processes. The identification of modern pigments allows them to be contextualized in illumination practices of the 19th century. Manuals of that time provide a wealth of information on specific illumination practices and the availability of writing and painting materials, which correlates with the actual artefacts.

Ag-Nanostars for the Sensitive SERS Detection of Dyes in Artistic Cross-Sections—Madonna della Misericordia of the National Gallery of Parma: A Case Study

In historical paintings, the detection of low amounts of pigments and dyes by Raman spectroscopy can sometimes be challenging, in particular for fluorescent dyes. This issue can be overcome by using SERS (surface-enhanced Raman spectroscopy) which takes advantage of the properties of nanostructured metal surfaces to quench fluorescence and enhance Raman signals. In this work, silver nanostars (AgNSs) are applied for the first time to real art samples, in particular to painting cross-sections, exploiting their effective SERS properties for pigment identification. The case study is the Madonna della Misericordia of the National Gallery of Parma (Italy). Cross-sections were analyzed at first by optical microscopy, SEM-EDS, and micro-Raman spectroscopy. Unfortunately, in some cross-sections, the application of conventional Raman spectroscopy was hindered by an intense background fluorescence. Therefore, AgNSs were deposited and used as SERS-active agent. The experimentation was successful, allowing us to identify a modern dye, namely copper phthalocyanine. This result, together with the detection of other modern pigments (titanium white) and expert visual examination, allowed to reconstruct the painting history, postdating its realization from the 15th century (according to the Gallery inventory) to 19th century with a heavy role of recent (middle 20th century) restoration interventions.

Fiber Optic Reflection Spectroscopy-Near-Infrared Characterization Study of Dry Pigments for Pictorial Retouching.

A deep comprehension of composition of pigments, employed nowadays in the field of pictorial retouch is considered essential for a deeper knowledge of their behavior with time once applied on artifacts. A commercially available set consisting of 27 pigments employed for the conservation of both historical and contemporary artworks has been characterized through Reflectance Spectroscopy in the VIS and NIR spectral range. The pigments included in the investigated set are classified into four categories: (i) dyes and colors from plants, (ii) modern pigments, (iii) pigments of own production and historical pigments, and (iv) natural earths. Recorded spectra were interpreted with the aim to detect existing coloring and filling phases and obtained results were compared with available data sheets: some inconsistencies were found, as well as lack of some compounds among the reported ones. Attributions were found for many features, even if in some cases detailed information for a comparison was not found in the literature, especially regarding NIR spectra. The proposed paper aims to provide a useful tool for the study of real artworks with a detailed overview of material characteristics in the visible and near infrared spectral range.

Study of Tattoo Colorants in Skin by Conventional and Polarized Light Microscopy.

Tattoos are a common practice in the 21st century. Although most modern pigments are organic and made of vegetable or plastic compounds, they still sometimes elicit an adverse reaction in the skin. Identifying the tattoo pigment in such biopsies is not always an easy task. To study how tattoo inks appear in the skin, we injected 14 different colors of commercial tattoo ink into normal skin obtained from a mastectomy specimen. One unstained section was obtained from each case, as well as one section stained with hematoxylin-eosin from each case. All sections were observed under the microscope. Stained and unstained sections were also examined under polarized light. We did not observe any modification of the ink color with the staining process with hematoxylin-eosin. However, some pigments appeared differently in stained and unstained sections than in the vial. Pink was the most difficult color to identify from the eosinophilic tissue. None of the colors showed any birefringent particles. However, in some unstained slides under polarized light, the color of the pigment appeared more similar to the one in the vial than in the stained slide.

Investigation of modern oil paints through a physico-chemical integrated approach. Emblematic cases from Valencia, Spain.

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.

Non-invasive identification of pigments in Japanese coloured photographs

This paper describes the first systematic analysis of 19th century Japanese coloured photographs. This unique Japanese technique followed the diffusion of photography taken up by Westerners. The photos were coloured by the painters of the School of Yokohama from ukiyo-e prints ateliers and were sold to travellers returning home as a souvenir from Japan. Although there are several museum collections throughout the Western world, this artistic technique has never been thoroughly investigated, due above all to the fragility of the artworks. In this study 22 photographs and a photo album cover from the Museum of Cultures (Lugano, Switzerland) were analysed by non-invasive infrared spectroscopy in order to identify the painting materials. A preliminary survey was carried out on reference pigments used in Japan in the 19th century, some of which are the same as those used in Western Europe, but many are particular to the Japanese school of arts. The reference pigments were analysed after extraction procedures taken from traditional recipes. Modern pigments such as “aniline colours” were also considered. The results provided insights into the painting materials, for example identifying Prussian blue, gofun, yamahaji, enju, shio, and rhodamine. The data confirmed the use of albumen paper and detected the application of a beeswax-based varnish for conservation purposes.

Determination of crystal phases in mixed TiO2 paint films by non-invasive optical spectroscopies

Modern pigments have been synthetically produced starting from the 19th century. Frequently, achievements in the synthesis technology have changed the physical characteristics of these inorganic pigments in order to improve their stability and coloring power. A clear example of this trend is represented by titanium white (TiO2) that evolved from the less performant anatase to a highly pure rutile crystalline structure. In this work, we propose a non-invasive method based on two complementary optical techniques, time-resolved photoluminescence and Raman spectroscopy, for determining the presence of these two polymorphs of titanium oxide in paint films. Results demonstrate that Raman spectroscopy is highly sensitive to anatase, whereas time-resolved photoluminescence allows the easy identification of rutile even when present in very low concentrations, up to a minimum value of 1.5 wt%. The complementarity and flexibility of the two spectroscopy techniques make the proposed approach promising for dating titanium white paints in modern and contemporary paintings on the basis of the presence of rutile and anatase polymorphs.

Deepening Inside the Pictorial Layers of Etruscan Sarcophagus of Hasti Afunei: An Innovative Micro-Sampling Technique for Raman/SERS Analyses.

The Hasti Afunei sarcophagus is a large Etruscan urn, made up of two chalky alabaster monoliths. Dated from the last quarter of the third century BC, it was found in 1826 in the small town of Chiusi (Tuscany- Il Colle place) by a landowner, Pietro Bonci Casuccini, who made it part of his private collection. The noble owner’s collection was sold in 1865 to the Royal Museum of Palermo (today under the name of Antonino Salinas Regional Archaeological Museum), where it is still displayed. The sarcophagus is characterized by a complex iconography that is meticulously illustrated through an excellent sculptural technique, despite having subjected to anthropic degradation and numerous restorative actions during the last century. During the restoration campaign carried out between 2016 and 2017, a targeted diagnostic campaign was carried out to identify the constituent materials of the artefact, the pigments employed and the executive technique, in order to get an overall picture of conservation status and conservative criticalities. In particular, this last intervention has allowed the use of the innovative micro-sampling technique, patented by the Cultural Heritage research group of Sapienza, in order to identify the employee of lake pigments through SERS analyses. Together with this analysis, Raman and NMR technique have completed the information requested by restorers, for what concerns the wax employed as protective layers, and allowed to rebuild the conservation history of the sarcophagus. In fact, together with the identification of red ocher and yellow ocher, carbon black, Egyptian blue and madder lake, pigments compatible with the historical period of the work, modern pigments (probably green Paris, chrome orange, barium yellow, blue phtalocyanine) have been recognized, attributable with not documented intervention during the eighteenth and twentieth centuries.

Thermal Decomposition of Lead White for Radiocarbon Dating of Paintings

ABSTRACTLead carbonates were used as cosmetic and pigment since Antiquity. The pigment, known as lead white, was generally composed of cerussite and hydrocerussite. Unlike most ancient pigments, lead white was obtained by a synthetic route involving metallic lead, vinegar and organic matter. Fermentation of organic matter produces heat and CO2 emission, leading to the formation of carbonates. As lead white is formed by trapping CO2, radiocarbon (14C) dating can thus be considered. We have developed a protocol to prepare lead white. We selected modern pigments for the experiment implementation and ancient cosmetic and paintings for dating. After characterization of the samples by XRD, thermal decomposition of cerussite at various temperatures was explored in order to select the appropriate conditions for painting samples. CO2 extraction yield, SEM and XPS were used to characterize the process. Thermal decomposition at 400°C was successfully applied to mixtures of lead white with other paint components (oil as binder, calcite as filler/extender) and to historical samples. We obtained radiocarbon measurements in agreement with the expected dates, demonstrating that thermal decomposition at 400°C is efficient for a selective decomposition of lead white and that paintings can be directly 14C-dated by dating lead white pigment.

IBA analysis of modern pigments and papers: new data on color alteration and limits for safe analysis

The response of modern, commercial drawing and painting media and papers to proton irradiation has been studied in a set of 180 colour/paper combinations aimed at assessing the potential of PIXE for the characterization of modern artistic materials. In the marks that appeared on some of the materials, during and after irradiation, colour changes have been calculated and used to set the beam current and the fluence limits for safe analysis.

Combined photoluminescence and Raman microscopy for the identification of modern pigments: explanatory examples on cross-sections from Russian avant-garde paintings

In conservation science, the identification of painting materials is fundamental for the study of artists’ palettes, for dating and for understanding on-going degradation phenomena. For these purposes, the study of stratigraphic micro-samples provides unique information on the complex heterogeneity of the pictorial artworks. In this context, we propose a combined-microscopy approach based on the application of time-resolved photoluminescence (TRPL) micro-imaging and micro-Raman spectroscopy. The TRPL device is based on pulsed laser excitation (excitation wavelength = 355 nm, 1 ns pulse width) and time-gated detection, and it is suitable for the detection of photoluminescent emissions with lifetime from few nanoseconds to hundreds of microseconds. In this work, the technique is beneficially applied for identifying different luminescent semiconductor and mineral pigments, on the basis of their spectral and decay kinetic emission properties. The spatial heterogeneities, detected in the micro-sample, are investigated with Raman spectroscopy (785-nm in CW mode) for a further identification of the paint composition on basis of the molecular vibrations associated with the crystal structure. The effectiveness and limits of the proposed combined method is discussed through analysis of a corpus of stratigraphic micro-samples from Russian Avant-garde modern paintings. In the selected samples, the method allows the identification of modern inorganic pigments such as cadmium-based pigments, zinc white, titanium white, chrome yellow, ultramarine and cinnabar.

An Archaeometric Characterization of Ecuadorian Pottery

Ecuadorian pottery is renowned for its beauty and the particularly rich colour of its pigments. However, a major challenge for art historians is the proper assessment of the provenance of individual pieces due to their lack of archaeological context. Of particular interest is the Jama-Coaque culture, which produced fascinating anthropomorphic and zoomorphic pottery from ca. 240 B.C. until the Spanish Conquest of 1532 A.D. in the coastal region of Ecuador. Using a combination of microscopic and spectroscopic techniques, i.e., transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), energy-dispersive x-ray spectroscopy (EDX), and scanning electron microscopy (SEM); we are able to characterize these pieces. We have found several kinds of iron-oxide based nanostructures in all the colour pigments we investigated for the Jama-Coaque culture, suggesting the same unique volcanic source material was used for their clay. Such nanostructures were absent from the pigment samples studied from other contemporary coastal-Ecuadorian cultures, i.e., the Tumaco-La Tolita and Bahía cultures. In the yellow pigments of goethite we find carbon nanofibres, indicating these pigments were subjected to a thermal treatment. Finally, in the blue, green, and black pigments we detect modern pigments (phthalocyanine blue, lithopone, and titanium white), suggesting modern restoration. Our results demonstrate the power of TEM, Raman, FTIR, EDX, and SEM archaeometric techniques for characterizing pieces without a clear archaeological context. Furthermore, the characterization of nanostructures present in such pieces could be used as a possible fingerprint for a provenance study.

Micro-XRF Investigation of Decoration Materials and Painting Techniques in Three 18th-19th Century Mosques in Berat, Albania

We will present here the data obtained from the examination with micro-XRF of a series of micro samples taken from the decorations of three mosques in Berat, Albania. These are parts of an Islamic religious complex situated at the central area of the old town and include the “Helvetia Tekke”, the King’s Mosque and the Bachelors’ Mosque, which were built or reconstructed during the second half of the 18th century and the beginning of the 19th century. Beside the architectural values of the buildings, the interiors of the monuments are decorated with paintings of the walls and the ceilings made of carved wood. The results of the measurements indicate that the preparation layer of the paintings on wooden ceilings was made of gypsum while that of the wall paintings was made of calcium carbonate. The palette includes the following inorganic pigments: lead white, gold, yellow and red ochre, vermilion, red lead, a copper based green, smalt and probably carbon black at Helvetia Tekke; green earth, yellow ochre, red ochre, red lead and cinnabar at Bachelors’ Mosque and red lead, orpiment and Indigo should have used for the original decorations of the ceilings in King Mosque, which are later overpainted with traditional pigments like yellow and red ochre, prussian blue and other modern pigments. Organic pigments, probably indigo and carbon black should have been used for the blue and black color. Similarities and differences observed between the monuments and indications about the painting technique as well as the degradation of some pigments will also be discussed.

Nano Particles and Nano Composites for Preservation of Historic Marble Minbars with Application on the Minber of Soliman Pasha Al-Khadim Mosque in Salah El-Din Citadel in Cairo, Egypt

Minbar, in Islam, the pulpit from which the sermon (khutbah) is delivered. In its simplest form, the minbar is a platform with three steps. Often it is constructed as a domed box at the top of a staircase and is reached through a doorway that can be closed. Soliman pasha Al-Khadim mosque in Salah El-Din citadel in Cairo is considered the first mosque with ottoman architectural style. This Minbar exposed to aggressive human intervention by mosque workers and archaeological crafts unity-ministry of antiquities in Egypt, to lose more of its historical and architectural values. Now this Minbar undergoes restoration process, they are removing all modern pigments and remains of last reconstruction in 2014 so we proposed some Nano particles and Nano composites for Preservation of it. The study started with the characteristics of the historic architectural elements of Mibars and their joining structural mortars in order to risk assessment and to define the necessary characteristics of the intervention retrofitting new materials, which will be used in the ongoing preservation work of these stucco architectural elements. To achieve such, several analyses and laboratory tests like ultra-sonic pulse method testing and uniaxial compression test were carried out to determine their basic, physical and mechanical properties, along with the microstructural properties determination using Mercury porosimeter. On the other hand, the morphological description, petrography, mineralogical and microstructural properties were determined using scanning electron microscope equipped by EDS, transmission electron microscopy TEM, polarizing light microscopy, XRD and XRF. The results proved the superiority of the samples that have been strengthened by nano lime concentration of 2% with Wacker OH 100 concentration in 5%.

Time-Resolved Photoluminescence Microscopy Combined with X-ray Analyses and Raman Spectroscopy Sheds Light on the Imperfect Synthesis of Historical Cadmium Pigments.

Recent studies have shown that modern pigments produced after the Second Industrial Revolution are complex systems characterized by a high level of heterogeneities. Therefore, it is fundamental to adopt a multianalytical approach and highly sensitive methods to characterize the impurities present within pigments. In this work we propose time-resolved and spectrally resolved photoluminescence (PL) microscopy for the mapping of luminescent crystal defects and impurities in historical cadmium-based pigments. PL analysis is complemented by X-ray diffraction, X-ray fluorescenceand Raman spectroscopies, andbyscanning electron microscopy to determine the chemical composition and crystal structure of samples. The study highlights the heterogeneous and complex nature of historical samples that can be associated with the imperfect manufacturing processes tested during the period between the 1850s and 1950s. The results also allow us to speculate on a range of synthesis processes. Since it is recognized that the stability of paints can be related to pigments synthesis, this research paves the way to a wider study on the relationship between synthesis methods and deterioration of cadmium pigments and paints. This rapid and immediate approach using PL can be applied to other semiconductor pigments and real case studies.

Unraveling the materials and techniques of post-Byzantine wall paintings: Is there a sole pictorial phase at the catholicon of Stomion, Central Greece?

Saint Demetrius of Stomion is a historical monastery placed in the geographical area of Larissa town, Greece, with a remarkable presence from its founding until nowadays. The monastery's present catholicon (main church) has been dated in the 16th century and its surviving wall paintings were constructed in 1758. In addition to the characterization of the materials applied, the purpose of this study is to determine the existence of a sole pictorial phase, that of the mid-18th century, or the occurrence of overpaintings. Additionally, the present study aims to begin the establishment of the documentation of materials and techniques of the late post-Byzantine iconographic guilds, which acted in Central and Northern Greece. The collected samples were analyzed by means of microscopic, spectroscopic and thermogravimetric methods. The use of fresco technique is implied by the major participation of calcium carbonate in all of the painting layers, its main contribution in the plaster layers and the microstratigraphic analysis of the samples' cross-sections, while the scarce and local presence of a proteinaceous material implies the limited use of egg-tempera technique for the highlights. The pigment analysis shows that mostly traditional pigments were used, including cinnabar, ferrous pigments (ochre, sienna, umber), minium, Naples yellow, massicot/litharge, green earth (celadonite), malachite, carbon and bone black, calcite, kaolinite and lead white. The absence of modern pigments, the consistency of all samples regarding microstratigraphy and applied materials, and the lack of the extensive use of an organic medium, strongly suggest the lack of overpaintings.

First principles study of the optical emission of cadmium yellow: Role of cadmium vacancies

We study the role of structural defects in the CdS-based cadmium yellow paint to explain the origin of its deep trap states optical emission. To this end, we combine a first principles study of Cd- and S- vacancies in the wurtzite (101¯0) CdS surface with experimental photoluminescence spectroscopy of the commercial hexagonal CdS pigment. Computational results clearly state that the presence of cadmium vacancies in the pigment surface alters the electronic structure of cadmium sulfide by forming acceptor levels in the gap of the semiconductor. Such levels are consistent with the optical emission from trap state levels detected in the CdS pigment. This finding provides a first step towards the understanding of the photo-physical mechanisms behind the degradation of this modern pigment, widely used in impressionist and modernist paintings.

Study of the Wall Paintings of the Cenador Del Leon in the Real Alcazar of Seville

The paintings on the walls of the Cenador del Leon located in the gardens of the Real Alcazar in Seville next to the Pabellon de Carlos V in the Jardin Ingles area have been studied. The components of the wall paintings cross-sections, which were prepared using small samples taken from the walls of Cenador del Leon, were characterized using infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis. The cross-sections of the collected samples indicated that the paint layer is well adhered to the preparation layer without any discontinuity, and only one carbonation layer exists at the top of the sequence of layers. These data suggest that the paint was applied on a fresco surface, and therefore, the adopted technique was fresco. Based on the different elements detected by EDX analysis of the cross-sections, the detected pigments included iron oxides accompanied by clay minerals (or earths) in the red pink, golden yellow and yellow colours, blue smelt for the blue colour and basic copper chloride (atacamite) for the green colour. In one sample, the particles were composed of Ba and S from barium sulphate and Ti and O from rutile titanium oxide due to a modern pigment.

Raman and Energy Dispersive Spectroscopy (EDS) Analyses of a Microsubstance Adhering to a Fiber of the Turin Shroud.

The Raman spectrum of a microsubstance, smeared on a fiber coming from the Shroud of Turin, was compared with numerous spectra published for old or modern pigment dyes, whole bloods, dried bloods, red blood cells, albumin, very ancient blood stains, and various "degradation" products of heme. Within the wavenumber measure accuracy, it is shown that all Raman lines detected above background could correspond to vibration frequencies found in biliverdin-derived compounds except a weak line that we tentatively attributed to amide I. Biliverdin is known as an oxidative ring cleavage product of the heme of blood. Energy dispersive spectroscopy (EDS) analysis of the sample confirms an elemental composition fully compatible with this hypothesis. Therefore, it is very likely that this microsubstance contains products of heme including heme/biliverdin-derived compounds and protein traces (amide I). Nevertheless, other measures will be necessary to confirm it. This method of identification, adding EDS to Raman spectrometry can be applied to nondestructive testing (NDT) of many other microsamples.

Airborne PCBs and OH-PCBs Inside and Outside Urban and Rural U.S. Schools.

PCBs appear in school air because many school buildings were built when PCBs were still intentionally added to building materials and because PCBs are also present through inadvertent production in modern pigment. This is of concern because children are especially vulnerable to the toxic effects of PCBs. Here we report indoor and outdoor air concentrations of PCBs and OH-PCBs from two rural schools and four urban schools, the latter near a PCB-contaminated waterway of Lake Michigan in the United States. Samples (n = 108) were collected as in/out pairs using polyurethane foam passive air samplers (PUF-PAS) from January 2012 to November 2015. Samples were analyzed using GC/MS-MS for all 209 PCBs and 72 OH-PCBs. Concentrations inside schools were 1-2 orders of magnitude higher than outdoors and ranged from 0.5 to 194 ng/m3 (PCBs) and from 4 to 665 pg/m3 (OH-PCBs). Congener profiles were similar within each sampling location across season but different between schools and indicated the sources as Aroclors from building materials and individual PCBs associated with modern pigment. This study is the first cohort-specific analysis to show that some children's PCB inhalation exposure may be equal to or higher than their exposure through diet.