Characterization of pigments and ligands in a wall painting fragment from Liternum archaeological park (Italy)

A Multi-Analytical Approach to Identify Colorants in the Qajar Painted Wooden Decorative False Ceilings, From Northwest Iran

The purpose of this study was to analyze the pigments used in the wooden paintings of Zarir Mosque, dating back to the Safavid era in Maragheh, Iran. These paintings, known as "Pardu," were commonly used for decorative false ceilings in various regions of Iran, particularly the northwest, during the Safavid and Qajar periods. Raman spectroscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy, multiband imaging, and optical microscopy were employed to examine the pigments. Fourier-transform infrared spectroscopy was also used to investigate the binder. The results indicated the use of orpiment, red lead, artificial ultramarine, carbon black, and gypsum for yellow, red, blue, black, and white pigments, respectively. Light blue colour was achieved by mixing gypsum and indigo, and gypsum was used as the primer layer in the painting. The presence of a protein-based binder, likely egg tempera, was confirmed through FTIR spectroscopy. The presence of artificial ultramarine suggests that these paintings were created after 1828, when it was first synthesized, placing them in the Qajar period. The presence of an inscription from 1280 AH suggests that these panels may have been produced during the extensive renovations of the mosque in 1280 AH (1864 AD), during the Qajar era.

Review of recent advances on the use of mass spectrometry techniques for the study of organic materials in painted artworks

The study of painted artworks using scientific methods is fundamental for understanding the techniques used in their creation and their appropriate conservation. The ethical constraints involved in the handling of, and sampling from, these objects has steered recent developments in the field of Heritage science towards a range of new non-invasive/non-destructive spectroscopic techniques capable of providing important insights into their elemental or bulk chemical compositions. Due to the inherent complexities of heritage artefacts, however, their organic components are especially difficult to study in this way and their identification and degradation pathways are thus often best investigated using mass spectrometric (MS) techniques. The versatility, sensitivity and specificity of MS techniques are constantly increasing, with technological advances pushing the boundaries of their use in this field. The progress in the past ten years in the use of MS techniques for the analysis of paint media are described in the present review. While some historical context is included, the body of the review is structured around the five most widely used or emerging capabilities offered by MS. The first pertains to the use of spatially resolved MS to obtain chemical maps of components in cross-sections, which may yield information on both inorganic and organic materials, while the second area describes the development of novel sample preparation approaches for gas chromatography (GC)-MS to allow simultaneous analysis of a variety of components. The third focuses on thermally assisted analysis (either with direct MS or coupled with GC-MS), a powerful tool for studying macromolecules requiring zero (or minimal) sample pre-treatment. Subsequently, the use of soft ionisation techniques often combined with high-resolution MS for the study of peptides (proteomics) and other macromolecules (such as oligosaccharides and triglycerides) is outlined. The fifth area covers the advances in radiocarbon dating of painting components with accelerator MS (AMS). Lastly, future applications of other MS techniques to the study of paintings are mentioned; such as direct analysis in real time MS (DART-MS) and stable isotope ratio MS (IRMS). The latter, having proven its efficiency for the study of lipids in archaeological artefacts, is envisioned to become a valuable tool for this area, whereas DART-MS is already being utilised to study the surface composition of various museum objects. Rapid technological advances, resulting in increased sensitivity and selectivity of MS techniques, are opening up new approaches for paintings analysis, overcoming the fundamental hurdle of sample size available for destructive analysis. Importantly, while the last decade has seen proteomics applications come to the fore, this review aims to emphasise the wider potential of advanced MS techniques for the study of painting materials and their conservation.

Comparison of binder compositions in Pompeian wall painting styles from Insula Occidentalis

Background

Although the pigment composition of Pompeian wall paintings has been the object of several studies, a comprehensive characterization of paint binder components is still lacking. This work aimed investigated at a molecular level the binder composition differences among wall paintings belonging to different periods of Pompeii’s history. Analytical investigations were performed on representative samples of the first, second, third, and fourth painting styles excavated from the house of Marcus Fabius Rufus (Insula Occidentalis). The application of sensitive experimental methodologies was complemented by historical knowledge to gain insight in painting techniques and materials used by Pompeian artists.

Results

Fourier transform infrared spectroscopy and Raman spectroscopy were used to investigate the organic components and pigments present in powders obtained from samples of the four painting styles. No proteinaceous components were detected in the samples with liquid chromatography-electrospray ionization-hybrid quadrupole/time-of-flight mass spectrometry. Liquid chromatography, gas chromatography with flame-ionization detection, and gas chromatography–mass spectrometry of polar and non-polar components extracted from powders were used to evaluate and compare the free amino acids, sugars, and fatty acids profiles.

Conclusions

Pigments and natural products (lipids, gums and wheat flours) were the main components of all samples. This supports the hypothesis that artists likely used water tempera for Pompeian wall paintings.

Graphical Abstract