Islamic glasses from Al-Andalus. Characterisation of materials from a Murcian workshop (12th century AD, Spain)

Rescue archaeological excavations at an urban glass workshop of the 12th century AD in the city of Murcia (Spain) have provided one of the few evidences of glass production in the ancient Islamic territory of Al-Andalus. This paper reports the results derived from a chemical–physical characterisation study carried out on a representative sample set of glass fragments and industrial debris from that workshop. The main objectives of the research were to contribute to the knowledge of the type of glasses produced and provide some insights into the technology developed to obtain different colours in glasses. The resulting data indicated that both high-magnesia plant ash (HMG) soda-lime-silicate and soda-lime lead-silicate glasses were produced. They also indicated a deep knowledge of glass colouring techniques, which suggests that a careful control over the glass melting processes was achieved. Among others, the occurrence of bulk-coloured silver yellow and copper ruby red transparent glasses prove the skills reached by Murcian glassmakers. These results shed new light on the Islamic glass technology of a geographical area in which, up to now, little compositional and technological data from glass workshops were available.     

Chemical and lead isotope compositions of lead artefacts from ancient Thracia (Bulgaria)

Using inductively coupled plasma–atomic emission spectrometry (ICP-AES), atomic absorption spectrometry (AAS) and instrumental neutron activation analysis (INAA) the concentration of Ag, As, Au, Bi, Cu, Fe, Ga, In, Ni, Sb, Sn, and Zn in 53 samples taken from archaeological finds dated to 4th–2nd century BC and found in the territory of ancient Thracia was determined. Additionally using inductively coupled plasma–mass spectrometry (ICP-MS) and MS for determination of the lead isotope ratios in the samples was carried out. On the basis of these analytical results using cluster analysis for grouping the samples on the bases of the similarity in chemical and isotopic content and the available data from the literature for lead ore deposits in the Balkan Peninsula, the geological origin of the investigated archaeological finds was evaluated. That confirms the expectation that sources of lead might be almost all possible deposits of lead ores on the Balkan Peninsula—from Lavrion through Chalkidiki to the Rhodope mountain. The result indicates that the Thrace did not utilize one single lead source continuously but that lead was provided according to availability from different production centers.     

Consolidation of paint on stained glass windows: Comparative study and new approaches

Stained glass windows belong to the most precious pieces of art in many European countries. Examples of heavily endangered paint on glass are reported in the literature and mainly related to condensation effects and air pollution, as stained glass windows preferably remain in their original architectural surrounding. Several surface coatings and paint treatments have been proposed to consolidate and protect degraded paint. Very often, the selection of the materials is based more on practical aspects than on scientific research. This study concerns the comparison of some traditional, modern and newly developed consolidants for the preservation of historic glass paintings. Experiments have been carried out with model painted glass samples simulating weathering phenomena of originals. Traditional materials like Paraloid B72, modern ones like SZA (proposed by the Fraunhofer-Institut für Silicatforschung, ISC), and three new consolidants prepared by the sol–gel method and based on different hybrid organic–inorganic alkyl-alkoxysilane systems have been considered. The adhesion, penetration, stability, hydrophobicity, mechanical and chemical resistance are properties and requirements tested to prove their effectiveness and range of use. The three new materials developed in this study for the consolidation of paint on glass have the potential to offer alternatives to existing materials. Nevertheless, further research is necessary before their application in restoration workshops can be recommended. A strategic approach is requested to avoid risks for these valuable historical originals and to contribute to the long-term preservation of the paint on stained glass windows in their original sites.     

The glass-melting furnace and the crucibles of Südel (1723–1741, Switzerland): provenance of the raw materials and new evidence of high thermal performances

Fifty crucible fragments and 10 fragments of the melting furnace of the forest glassworks of Südel (1723–1741, Ct. Luzern), were analyzed by petrographic, mineralogical and chemical techniques in order to assess the temperature reached in the melting chamber and to find out which raw materials were used to make the crucibles and the melting furnace. Since the crucibles were used in the melting furnace, the temperature estimations were based on both the crucibles and the refractory fragments, as they were parts of the same system. The temperature range in the melting chamber, estimated by the structural order of the new-formed cristobalite, points to a temperature range between 1350 and 1500 °C. However, three crucible samples recorded extreme temperatures as high as 1650 °C, suggesting very high flame temperatures for wood fuel. The analyzed red bricks were made with local calcium-poor clay. One of them was tempered with refractory fragments, demonstrating an in-house production and the recycling of such a material after its use. The crucibles and the refractory bricks were made with the same refractory clay. The former using unprocessed clay and the latter blending clay with chamotte. A comparison with Sidérolithique clayey sand samples from the Swiss Jura, shows strong affinities which may rule out the archaeological hypothesis of an exclusive provenance of such clays from Germany, suggesting an import from the Swiss Jura mountains.     

Archeaometallurgical finds from Barsinia,Northern Jordan: Microstructural characterization and conservation treatment

Within the framework of an excavation project aimed to systematically characterize the various aspects of settlement and activities in Northern Jordan, a considerable collection of slag lumps and iron artifacts of different forms and typologies excavated from the archaeological site of Barsinia were collected. Excavations have revealed other metallurgical materials such as pottery tuyeres and furnace-like structure. Studying those finds was important because of their archaeological and technological interests. For the analytical and metallurgical study, X-ray diffraction was used to identify the mineralogical composition of samples. Inductively coupled plasma-optical emission spectrometer, energy dispersive X-ray and X-ray fluorescence spectrometer were used to determine the accurate elemental composition of these finds. Furthermore examinations by using metallographic, polarizing microscope and scanning electron microscopy were employed to diagnose the characteristic morphology and environmental effects of these archaeometallurgical finds. Microstructural investigations emphasized that iron production processes were performed locally at the archaeological site of Barsinia even if the iron ores were imported from other mining location in Jordan. Direct or “bloomer” was the main method used for smelting iron ores followed by smithing methods to locally produce iron artifacts. This, most probably, was the state of technology from the Bronze Age to the Byzantine period. To ensure the stability of these deteriorated finds for future research, required treatment and conservation processes were successfully carried out.     

Archaeometric and geological constraints for the provenance of carbonatic breccias used in monumental works along the Flaminia Consular Road (Umbria-Marche, Central Italy)

Along the Umbria-Marche stretch of the Flaminia Consular Road (220 B.C.) several archaeological finds of the most important monumental works, are well preserved. The stones, employed to build many bridges, substructions and sewerages, are represented by carbonatic breccias whose geological environment of formation and source areas had never been established. On the basis of mineralogical, petrographic and micropalaeontological analyses, two groups of these lithotypes employed in Roman age were distinguished: “monogenic carbonatic breccias” only constituted by clasts of the Maiolica Unit (Late Jurassic – Early Cretaceous) and “polygenic carbonatic breccias” made of fragments (in different proportions) of Calcare Massiccio (Early Jurassic), Corniola (Early Jurassic), Maiolica (Late Jurassic – Early Cretaceous) and Scaglia Rossa (Late Cretaceous – Early Paleogene) Units. The possible source areas of the breccias are compatible with stratified slope-waste to scarp-base deposits of periglacial origin belonging to the Upper Pleistocene. In particular, among the seven investigated areas, we pointed out the most probable provenances (Monte Faeto-Colle, Costacciaro, Scirca, Foci, Secchiano) along the flanks of the Apennine Mesozoic chain of the Umbria and Marche regions. Although the Romans could have exploited the whole thickness of some outcrops (now disappeared) of these carbonatic lithotypes at the deepest part of the valleys, we have constrained a local provenance of the breccias so commonly used in the monumental works of the Flaminia.     

Chemical analyses of ancient glass findings excavated in the Venetian lagoon

Although Venice is regarded as being one of the most important centres of glass manufacture and trade in Western Europe, little is known about the origins of the Venetian glassmaking. Some archaeologists suggest there is a continuity in the history of glass making, in its transplantation from the Roman centres of the mainland (Altino and Aquileia), first to some islands of the lagoon, and later to the town. Some others, instead, think that there was no continuity at all and that the art of glassmaking was imported in Venice from the Islamic glass factories of the Middle East. Of great help in answering this and other technological questions is the information about the composition of ancient glass from well-dated excavations that allows to conclude on the early technology, sources of raw materials and long-distance trade. Some significant glass findings, including fragments of pots used for glass melting, were found on the island of Torcello and, more recently, in two emergency excavations in the historic centre of Venice. In this paper, the chemical composition of a large set of glass findings (and related materials) from the Venetian lagoon dating from the 7th to the 13th centuries is determined by X-ray microanalysis in order to throw new light on the glassmaking technology in the early centuries of the Venetian tradition. The results show that in this period there occurred a gradual transition from the Roman technique (a two-ingredient formulation with silica-lime sand and natron as a fluxer), towards the use of silica sand and soda plant ash. There is evidence, therefore, for a production continuity with the Roman period (melting pots and glass scraps with a natron-based composition), yet restricted to transparent blown items. No evidence was found for a local production of glass tesserae for the mosaics of the church of St. Maria Assunta in Torcello.     

The binding media of the polychromy of Qin Shihuang's Terracotta Army

The “Terracotta Army” is a worldwide known archaeological finding in China. It is a part of the burial complex of the emperor Qin Shihuangdi (259–210 BC), which is still under excavation and study. The fact that the sculptures, chariots and weapons of the First Chinese Emperor's Terracotta Army were originally all painted in bright colours is still not widely known. The chemical characterisation of the paint medium was performed through an analytical procedure based on GC-MS. The proteinaceous binder was identified for the first time through a desalting procedure used in proteomics. The identification of egg as a paint binder is extremely interesting in terms of the historical significance of the work of art itself and important in terms of the method of conservation. Moreover it represents one of the first steps towards an understanding of the painting technique used on ancient sculptures in China, of which – despite their fame – nothing is yet known.     

Silica glass interaction with calcium hydroxide: a surface chemistry approach

The study of the interaction between silica glass and saturated Ca(OH)₂ solutions can be a useful approach to resolve the problem of the adhesion between lime-sand mortar and clay bricks. Since it is reasonable that the silica–calcium hydroxide system well simulates a brick–mortar system, experimental observations concerning the interaction of silica glass and this strong basic solution should be of value for the comprehension of the chemical reactions that could take place at the mortar–brick interface, maybe affecting the adhesion between the two building materials. We demonstrated the effects of saturated Ca(OH)₂ solutions on commercial pure silica glass (fused silica) and on silica films obtained via a sol–gel process by means of dip-coating. Silica samples were dipped in the solutions at different temperatures (room temperature, 60 and 80 °C) and at different time intervals (1 and 21 h) and then they were analysed by means of surface techniques: X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and atomic force microscopy (AFM). It has been shown that Ca(OH)₂ reacts with the silica glass network. The experimental results clearly show a very different behaviour of sol–gel silica with respect to fused silica, probably because of their different nanostructure. Many problems concerning the interaction of silica and Ca(OH)₂ are still to be solved, but the results of this research strengthen the idea that adhesion between lime-sand mortar and clay bricks is caused not only by carbonation of calcium hydroxide contained in the mortar, but even by some chemical reactions involving the brick constituents and calcium hydroxide itself. The final products, calcium silicates, may induce a chemical continuity between lime-sand mortar and clay bricks.     

A multi analytical approach to discriminate the Italian colored marble “Portasanta” from Portasanta “Marmor Chium” (Greece)

The “marble” Portasanta from Caldana (Grosseto, Italy) takes its name from the strict resemblance to the ancient Marmor Chium (also this called Portasanta) coming from the island of Chios in Greece. In this work, a complete characterization of the Italian Portasanta was made: chemical (X-ray fluorescence and isotopic analyses), mineralogical (X-ray diffraction on the bulk sample and on insoluble residue after acid attack), physical (water accessible porosity and imbibition coefficients), petrographical (optical microscopy) and mechanical (compressive strength test) analyses have been carried out in order to obtain a better distinction between Italian and Greek “marble”, sometimes mistaken. The Portasanta from Caldana (Italy) was quarried surely in the sixteenth century, but a possible use of this material during Roman time is still in doubt. The study of samples from some Tuscan archaeological sites (Torraccia di Chiusi, Siena and Roselle, Grosseto) allows us to confirm the use of Portasanta from Chios for the Torraccia site and that of Caldana for Roselle.     

The scientific approach to the restoration and monitoring of mural paintings at S. Girolamo Chapel – SS. Annunziata Church in Florence

The scientific approach to the restoration and monitoring of mural paintings, at S. Girolamo Chapel – SS. Annunziata Church in Florence, is reported as a fruitful example of the synergic collaboration between restorers and scientists in the planning and development of conservative interventions. Before restoration, the painting technique and the state of preservation of the pictorial cycle have been investigated firstly by close examination of the painted surfaces and then by optical and/or SEM-EDS microscopy and μFT-IR spectroscopy on appropriately selected samples. In particular, the original constituent materials and those belonging to subsequent restorations were characterized together with those originating from decay processes. In this mural painting cycle, a peculiar “fresco” technique has been used although an auxiliary binder for pigment distemper has been also employed. The use of this technique, sometimes in an improper way together with uncorrected restoration interventions, are the main responsible of the unsatisfactory state of conservation of many painted areas. Preliminary conservation trials and scientific studies were carried out to design the most convenient restoration intervention and to verify the correctness and non-invasive of the necessary operations. Special attention was devoted to cleaning procedures, continuously monitored by a physico-chemical methodology, mainly based on microinvasive, microscopic and spectroscopic investigations, to evaluate the efficiency, advantages and drawbacks of the proposed cleaning procedures and define the most appropriate ones. Finally, specific decay markers have been recognized, by a comparison of the results obtained from the detached samples with those deriving from artificially aged models, to be used for a correct future monitoring and maintenance of the wall paintings.     

Neorenaissance/Neobaroque stained glass windows from Madrid: a characterisation study on some panels signed by the Maumejean Fréres company

This paper reports results derived from a chemico-physical characterisation study undertaken on an important ensamble of early 20th century stained glass windows from Madrid and signed by the prestigious and well-known Maumejean Fréres company. The study is part of an on-going project of restoration and conservation carried out by the National Glass Centre Foundation (FCNV, La Granja de San Ildefonso, Segovia, Spain). The basic aim of the research was to assess their current state of conservation and to study the degree of damage suffered throughout the last century by different materials employed in their production, namely colourless and coloured glasses, grisailles, lead cames, and putties used to fix glass pieces into the lead cames. Selected samples from these materials were characterised through optical microscopy (OM), X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX), VIS spectrophotometry, and X-ray diffraction (XRD). As a general rule, most of them presented an acceptable state of conservation, without any of the known degradation phenomena of more ancient stained glasses (e.g. Medieval, Renaissance, etc.). However, some remarkable alterations were observed. Important deposits of soot and dirt particles coming from a polluted urban environment were detected, producing a slow blackening of the panels. Resulting data have been useful to design and optimise a combined conservation and restoration strategy in the recovery of this valuable legacy of early 20th century stained glass windows from Madrid.     

A methodology for the identification of glass panes of different origin in a single stained glass window: Application on two 13th century windows

The chemical composition of 11 glass panes originating from two 13th century non-figurative windows were analyzed by means of Scanning Electron Microscopy–Energy Dispersive X-ray system (SEM-EDX). The windows were discovered in the back-wall of the triforium during the restoration of the choir of the cathedral St. Michael and St. Gudule in Brussels (Belgium). In order to determine if these windows were fabricated with glass of different origin or not, the compositional difference between the panes were compared with the variation in composition as a result of the following causes: (1) compositional fluctuation between panes cut from the same sheet of glass, (2) compositional fluctuation caused when panes are cut from different sheets that were made with the same batch, (3) compositional fluctuation caused when the glass is made from different batches at the same production center, and (4) compositional fluctuation as a result of glass produced at different fabrication centers.     

Investigating the spectral capability of QuickBird data to detect archaeological remains buried under vegetated and not vegetated areas

The spectral capability of satellite QuickBird imagery for the identification of archaeological marks linked to the presence of buried remains is here discussed for two medieval archaeological sites in the South of Italy. The considered test sites present complex topographical and morphological features, typical of many medieval settlements, which make archaeological prospection with any remote sensing technologies difficult. Results from the performed investigations showed that the satellite QuickBird imagery can be a valuable data source for reconstructing the urban shape of buried settlements up to single building scale. Such analyses can be useful for detecting locations and extracting features of archaeological sites especially prior to any excavation work and for increasing the cultural value of historical sites.     

The characterization of commercial artists’ alkyd paints

There is little information in the conservation literature with respect to artists’ alkyd paints; thus, artists and conservators are somewhat at a loss about how to use and treat alkyds. Recently, analytical methods have been developed to identify the components in these polymers (oil modified polyesters), rates of cross-linking and mechanical properties. Presented in this paper are some of the characterization results of artists’ alkyd paints using THM (thermally assisted hydrolysis and methylation) gas chromatography– mass spectrometry (THM–GC/MS) and Fourier transform infrared spectroscopy–attenuated total reflectance (FTIR–ATR). Four brands of artists’ alkyd paints containing alkyd resin have been analysed; one containing a phthalic anhydride and pentaerythritol based alkyd resin, two containing isophthalic acid and pentaerythritol based alkyd resins, and the final one containing both phthalic anhydride and isophthalic acid and pentaerythritol based resins among the colours studied.     

Different methods for soluble salt removal tested on late-Roman cooking ware from a submarine excavation at the island of Pantelleria (Sicily,Italy)

This paper deals with the comparative evaluation of different procedures of salt extraction designed for archaeological ceramics from submarine burial environments. The experimental work was carried out on a particular type of late-Roman cooking ware finds (Pantellerian ware) found in a shipwreck near the shoreline of the Island of Pantelleria (Sicily). The studied ceramic test-pieces were first recognised in terms of bulk characteristics (mineralogy, petrography and chemistry). SEM-EDS observation allowed verification of the presence of various secondary minerals at the surface and in the pore spaces formed after the prolonged permanence in seawater under oxidising or reducing conditions. Pore-size distribution was also determined in the same fragments that had been subjected to the salt extraction routines. Three salt extraction methods were tested: two methods based on diffusion processes (water immersion under stationary conditions and under mechanical stirring conditions) and one method based on both diffusive and advective processes (multiple packages of sepiolite). The obtained experimental data allowed us to identify strengths and weaknesses of the tested procedures with practical spin-off for archaeologists and restorers (efficiency, kinetics, compatibility with the ceramic substrate, costs and simplicity of use). Salt extraction under mechanical stirring was the most effective method and, for this reason, is suitable for laboratory fieldwork during or immediately after submarine archaeological excavations. Similar advantages are also intended for the preliminary treatments of the most precious findings prior to museum storage.     

Analysis of lapideus materials from the columns of the cathedral of St Maria in Randazzo (Catania,Italy) and from their ancient origin quarries

Lava columns from the cathedral St Maria of Randazzo (Catania, Italy), were studied in order to establish the classification of these rocks and to investigate their origin. At the beginning of the XIX century, some columns of the old frame of the nave were removed to build the dome and stored in a fornix beneath the cathedral. Samples were taken directly from these columns. The specimens underwent petrographic investigation through optical microscopy, X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR) and chemical analyses of major and trace elements through X-ray fluorescence (XRF). Some trace element (Sr, Rb, Y, Zr and Nb) concentrations were assessed through non-destructive analyses, performed with a portable X-ray device which can detect homogeneous concentrations of such elements on the columns of the cathedral. According to chemical data, these rocks can be classified as mugeariites whose mineral assemblage is given by plagioclase (mostly andesinic), augitic pyroxene, olivine, magnetite and, occasionally, apatite. In order to investigate the origin of the material used for the columns, a comparative examination was conducted between the column samples and specimens collected from quarries in the surrounding area of the town of Randazzo (Randazzo and Maniace quarries and the 1536 lava flow). The correlation with the Randazzo quarry proved to be excellent.     

La Medusa by Caravaggio: characterisation of the painting technique and evaluation of the state of conservation

The oil painting “La Medusa” executed by Caravaggio at the end of the XVI century on a wooden shield, was investigated by integrated physical–chemical and analytical methodologies in order to obtain scientific data capable of elucidating the state of conservation and the painting technique. Optical (OM) and electronic (SEM-EDS) microscopy, micro-FT-IR spectroscopy, gas chromatography–mass spectrometry (GC–MS) and pyrolysis GC–MS were applied on two microfragments and some organic samples obtained by solvent extraction using the swab cleaning technique. The obtained results indicated that Caravaggio probably reused an old shield as a previous gypsum preparation layer has been detected under the original painting layers. He used white lead, natural earths, verdigris and lead–tin yellow type I mixed with drying oils to paint. The considerable amount of amorphous particles of copper chlorides found in the green pigment verdigris suggests that it could have been produced according to the ancient recipe of verde salsum described by Theophilus. Mordant gilding has been identified on the upper part of the shield that can be related to an abandoned experiment to give the painting a mirror-like reflecting effect. Three different varnishes layers have been detected above the painted surface. The original and restoration varnishes have been identified and they contain a mixture of drying oil, mastic and turpentine and some beeswax. Cleaning tests, performed with different organic solvents, suggest the use of isopropyl alcohol as cleaning agent because it is less efficient in comparison to others solvents; thus it ensures a careful and controlled removal of the varnishes.     

Detection of diagenetic alterations by Spectroscopic Analysis on Archaeological Bones from the Necropolis of Poseidonia (Paestum): A case study

Understanding the chemical and physical alteration in archaeological bones, occurred after burial, is very interesting for researchers. In this paper, we present a study on the diagenetic alteration of human archaeological bony tissues from Paestum (South Italy), by combining complementary spectroscopic techniques, such as solid-state nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and X-ray diffraction. In particular, ¹³C nuclear magnetic resonance–cross polarization-magic angle spinning (¹³C NMR CP-MAS) spectroscopy allows to identify and discriminate the adsorbed calcite, that is a diagenetic contaminant, from the structural one of apatite and ¹H NMR-MAS spectroscopy shows how the degradation of organic phase of collagen is related to the time. The NMR data are combined with crystalline index, measured by X-ray diffraction, and with the splitting factor obtained by infrared spectroscopy. Moreover, the evaluation of the relative content of biogenic structural carbonate and of diagenetic fluorine is reported.