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In a polychrome artefact, coloured paint layers are applied on architectural elements or sculptures. Paint layers are made up of the colour, which is most typically an inorganic pigment and, with the exception of frescos, an organic binder, which enables the pigment to be dispersed and applied with a brush. From an analytical point of view the characterisation of organic paint binders is very challenging: the organic matter represents a very small amount of the total weight of the sample which is very small and aged. In this paper we describe the analytical approach applied for the characterisation of samples collected from a selection Gandhara polychromies. The analytical strategies and techniques employed are described and examples of the results obtained are presented., Restauro Archeologico, Vol. 27 No. 1 (2019)

This paper presents the results of an investigation of organic binding media detected in samples from the Mycenaean wall-paintings at the “Palace of Nestor” in Pylos (Western Messenia, Greece): samples dated from the Late Bronze Age (ca. 1200 BC). This is the first scientific study to be conducted on organic binding media in Mycenanean painting, and it is a study that aims to contribute significantly towards our understanding of the original painting techniques used during the Bronze Age. The analytical procedures employed for the detection and characterization of the organic substances preserved within the paint layers (proteinaceous materials, lipids and plant gums), were based on chromatography/mass spectrometry techniques (PY–GC/MS, GC/MS). The most significant results, highlighting an a secco painting technique, are herein reported and discussed.

An innovative GC/MS procedure for the characterization of organic materials in samples from works of art was developed. It is based on a multistep chemical pretreatment of the samples based on the ammonia extraction of proteins and polysaccharide materials, in order to separate them from lipid and resinous materials. The extraction is then followed by the separation and purification of proteinaceous and polysaccharide materials before hydrolysis, based on the use of monolithic sorbent tip technology with a C4 stationary phase. Lipids and resins are saponified/salified separately. Three fractions are generated and analyzed separately by GC/MS, thus enabling a quantitative analysis to be performed on aldoses and uronic acids, amino acids, mono- and dicarboxylic aliphatic acids, to determine polysaccharide, proteinaceous, and glycerolipid materials and molecular pattern recognition for the natural resin and wax components. With this analytical procedure, for the first time, glycerolipids, natural waxes, and proteinaceous, resinous, and polysaccharide materials can be simultaneously characterized in the same microsample from painted works of art. This new analytical approach prevents any analytical difficulties arising when the sample is divided into several different aliquots to be chemically processed separately, in order to characterize the various classes of organic materials. The procedure was successfully applied to samples from paintings from the Bamiyan Buddhas and a panel painting from the 15th century, highlighting the occurrence of glycerolipids, animal and plant resins, proteinaceous and polysaccharide materials.

This paper presents an analytical GC-MS procedure to study the chemical composition of plant gums, determining aldoses and uronic acids in one step. The procedure is based on the silylation of aldoses and uronic acids, released from plant gums by microwave assisted hydrolysis, and previously converted into the corresponding diethyl-dithioacetals and diethyl-dithioacetal lactones. Using this method only one peak for each compound is obtained, thus providing simple and highly reproducible chromatograms. The analytical procedure was optimised using reference samples of raw plant gums (arabic, karaya, ghatti, guar, locust bean and tragacanth, cherry, plum and peach gums), commercial watercolours and paint layers prepared according to ancient recipes at the Opificio delle Pietre Dure of Florence (Italy). To identify gum media in samples of unknown composition, a decisional schema for the gum identification and the principal component analysis of the relative sugar percentage contents were employed. The procedure was used to study samples collected from wall paintings from Macedonian tombs (4th-3rd centuries bc) and from the Mycenaean "Palace of Nestor" (13th century bc) in Pylos, Greece. The presence of carbohydrates was ascertained and plant gum binders (fruit and a mixture of tragacanth and fruit tree gums) were identified in some of the samples.

A unique sample of ink from an inkwell in the Schoyen Collection allegedly found at Qumran has been subjected to analyses by several analytical techniques: GC-MS, proteomic analysis, PXRD, Raman, (ATR) FT-IR, LIBS, ICP-MS and MS. The results reveal to an unexpected level of detail how the ink was manufactured, which gives insight into, the industrial processes and craftsmanship that were practiced at the Qumran settlement during the Second Temple period (100 BCE-CE 70). The identified minerals and other organic and inorganic materials are sufficiently multiple and diverse that it is probable that this specific ink can be recognized if analyses. of inks are performed on manuscripts from Qumran and other locations in Israel and the Middle East. The present work exposes a distinct and unique possibility to shed light on early Jewish manuscript controversies, including their provenance. (C) 2012 Elsevier Ltd. All rights reserved.

[spa] El estudio de muestras de pintura persigue diferentes objetivos. Por un lado, identificar los materiales y técnica de la pintura de una época y por lo tanto el know-how de un período histórico. Por otra parte, estudiar la degradación y el envejecimiento de estos materiales con el fin de evitar su desaparición. Al mismo tiempo, se pretende también elegir y aplicar los materiales más adequados en los procesos de restauración y conservación, así como las mejores condiciones de exposición. Desde un punto de vista físico-químico, las pinturas son matrices complejas formadas por capas de una mezcla heterogénea de materiales orgánicos e inorgánicos, mezclados en proporciones desconocidas y dispuestos en capas micrométricas. Además, estos materiales experimentan interacciones entre ellos y un heterogéneo envejecimiento con el tiempo y a exposición a contaminantes, luz y condiciones de conservación, tales como humedad y temperatura. Como resultado, las pinturas no son objetos estáticos, sino sistemas complejos que constituyen una problemática difícil para el químico analítico. La naturaleza de las pinturas requiere, además, de un enfoque de cartografía 2D con el fin de poder, no sólo caracterizar e identificar los materiales presentes, sino también para obtener su distribución en la muestra. El objetivo general de esta tesis es el de rellenar algunas lagunas en el análisis y la caracterización de los sistemas pictóricos. Completar el conocimiento parcial obtenido anteriormente es el hilo conductor, aunque cada capítulo tiene una entidad propia. Con este finalidad se siguieron diferentes caminos contemporáneamente: el desarrollo de métodos de preparación de muestras y los procedimientos analíticos para el estudio de las muestras de pintura, y la caracterización de la composición de los materiales y de sus procesos de degradación mediante la aplicación de las metodologías analíticas desarrolladas. Los diferentes capítulos tratan las siguientes problemáticas: Synchrotron radiation based micro imaging FTIR to the study of painting cross-sections, Characterisation and distribution of oxalates in mural painting samples, MS and SR based techniques for the identification and distribution of painting materials in samples from works of art, GC/MS characterisation of saccharide materials in samples from works-of-art y GC/MS analytical procedure for the characterization of lipids, terpenoidresins, polysaccharide and proteinaceous materials in the presence of interfering inorganic pigments in the same micro sample. La tesis demuestra la capacidad de Radiación Sincrotrón para la obtención de imágenes FTIR en modo de transmisión y la capacidad de Cromatografía de gases/espectrometría de masas para el estudio de los materiales de la pintura y sus productos de degradación, haciendo especial atención a los materiales sacarídicos. La complementariedad de las técnicas ha sido destacada permetiendo una visión global del conjunto.

Identification of proteins in paintings and polychrome objects is a challenge, which requires the development of tailored analytical approaches. In the present study, a targeted proteomics approach was developed for discriminating among the three most common proteinaceous materials used as paint binders, i.e. milk, egg, and animal glue. In this study a specific database of peptides was created based on tandem MS analyses of tryptic digests of several paint samples collected from a variety of art objects of different ages and conservation conditions. Specific peptide markers of each protein were then selected and monitored by LC-MSMS in Multiple Reaction Monitoring (MRM) ion mode, together with their specific precursor ion-product ion transitions, as defined by their unique amino acid sequence. The developed method enabled a sensitive and reliable detection of the target peptides in a selection of case studies, leading to the unambiguous identification of the proteins used as paint binders. The method showed greatly increased sensitivity compared to currently available strategies.

A chemical investigation of the organic paint binders of the Giant Buddhas of Bāmiyān was performed using an analytical approach based on mass spectrometry, combining traditional gas chromatography/mass spectrometry protocols with advanced proteomics methodologies. The research was carried out on a selection of rescued fragments. The data revealed the use of egg proteins as the paint binders of the original layers, in accordance with the traditional use of this proteinaceous medium in antiquity, spanning from the Mediterranean basin to the Far East, and already in the Bronze Age. Egg tempera was thus known to artists of the region in the first centuries AD, probably also due to the position of the Bāmiyān valley, which was connected to the Silk Road. Milk was found in the first historical overpaintings. A new proteomics approach was used, which was able to identify the source of the milk proteins present in the restoration layers, despite their age and degradation. In particular cow's and goat's milk were both found, in agreement with the documented presence of rich pastures in the Bāmiyān valley when the historical restorations were carried out. Investigating the materials of the Giant Buddhas not only enabled us to obtain isolated data on these invaluable works of art, which are now lost, but contributes to understanding the big ªpuzzleº of our past and the development of our culture, by implementing and supporting written sources, stylistic and anthropological studies with molecular data.

An organic binder was identified in the painted fragments from the Canaanite palace of Tel Kabri, Israel. Recently dated to the late 18th century B.C.E. by 14 C, Tel Kabri is the most ancient of the Eastern Mediterranean sites in which Aegean style paintings have been found. The application of pigments was suspected to be using an organic binding medium, particularly for the Egyptian Blue pigment. Samples of blue paint were examined using evolved gas analysis-mass spectrometry (EGA-MS) in order to overcome the analytical challenges imposed by highly degraded aged proteinaceous materials. Egg was identified as the binder based on the presence of hexadecanonitrile and octadecanonitrile, confirming the use of a secco painting technique. Lysozyme C from Gallus gallus was detected by proteomics analysis, confirming the presence of egg. To our knowledge, this is the earliest use of egg as a binder in Aegean style wall paintings.