Spectroscopic and chromatographic studies of sculptural polychromy in the Zhongshan Grottoes (R.P.C.)

The sculptural polychromy in the Zhongshan Grottoes, sited in northwest China, has been investigated in terms of chemical composition of employed materials and pigments, state of conservation and painting technique. Raman analysis, Fourier-transform infrared analysis, analysis through energy-dispersive X-ray spectrometry coupled to scanning electron microscopy and pyrolysis coupled to gas chromatography and mass spectrometry were applied. Six analyzed samples showed silicates and kaolin as main components of the ground layers. Also lead white has been found in these layers. Minium, red-earth and mercury sulfide are the red pigments detected in the polychromy. A mixed use of malachite and atacamite has been detected in three green samples. Optical characteristics of atacamite and malachite found in the samples indicate a synthetic origin. The presence of a synthetic organic pigment such as phthalocyanine chlorinated pigment was also revealed. Ultramarine blue pigment, obtained by purification of lapis lazuli, has been detected in the blue sample. As for the binders used, fatty materials and siccative oil were found.     

Degradation of lead-based pigments by salt solutions

Interactions of lead-based pigments with a number of inorganic salts, one of the most dangerous degradation agents of wall paintings, were studied under laboratory conditions. The results were used to interpret colour changes observed in 11th century frescoes from the church of Saint George in Kostoľany pod Tríbečom, the oldest preserved wall paintings in Slovakia. Interactions of selected pigments (lead white, massicot, red lead) with different salt solutions were performed within long-term laboratory experiments. We used a selection of naturally occurring salts (Na₂SO₄, MgSO₄, CaSO₄, NaCl, NaNO₃, Ca(NO₃)₂, Na₂CO₃, K₂CO₃ and urea) and, additionally, a range of synthetic salts that are often applied to the wall paintings during their cleaning and conservation (NaHCO₃, KHCO₃, (NH₄)₂CO₃, NH₄HCO₃). The reaction products were identified by X-ray powder diffraction. Red lead (Pb₃O₄) has a tendency to darken in all salt solutions containing dissolved atmospheric CO₂ due to disproportionation to plattnerite (PbO₂) and cerussite (PbCO₃). Massicot (PbO) in a wet state reacts with atmospheric CO₂ to form hydrocerussite and finally cerussite. Lead white (PbCO₃ and Pb₂CO₃(OH)₂) reacts with sulphates, carbonates and chlorides to form their respective salts in high yield and, sometimes, without any apparent colour change. Samples taken from the dark brown parts of the wall paintings in Saint George's church were analysed using laboratory X-ray powder microdiffraction. The presence of hydrocerussite, cerussite, plattnerite and lead magnesium carbonate was revealed. According to the results of laboratory experiments, the original lead-based pigment of the now darkened parts was red lead.     

The origin of syngenite in black crusts on the limestone monument King's Gate (Belgrade Fortress,Serbia) – the role of agriculture fertiliser

Black crusts formed on limestone built into the King's Gate represent the most important process in stone deterioration that is occurring in this part of the monumental complex of the Belgrade Fortress (Serbia). Of special importance is the association of salts (namely gypsum and syngenite). Syngenite is a common secondary deposit on granite monuments and on medieval stained glass (i.e., on K-containing materials). However, its appearance over calcareous substrates is not apparent, particularly in cases where cement mortar was not used for bounding. The origins of the potassium and sulphate ions required for syngenite formation are related to meteoritic water, which penetrates the soil above the arch of King's Gate. Water dissolves some soil components and becomes enriched with various ions before coming into contact with the limestone blocks. Enriched water contains two times more K⁺ and SO₄^2? ions than pristine meteoritic water does. The source of the required ions is potassium-sulphate that is present in agricultural fertilisers that are used above the monument. The proposed mechanism for syngenite formation was additionally supported with laboratory experiment. The results of X-ray diffractometry and SEM-EDS analyses of limestone treated with potassium-sulphate solution and sulphuric acid suggest the possibility that the syngenite was formed over calcite:CaCO₃ + K₂SO₄ + H₂SO₄ → K₂Ca(SO₄)₂ H₂O + CO₂↑However, the complex mechanisms of gypsum and syngenite formation under natural conditions (variable concentration of potassium and sulphate ions, intermediates phases, temperature changes, humidity, the amount of disposable water etc.) do not exclude the possibility of syngenite formation over gypsum.     

Nanoparticles of calcium hydroxide for wood deacidification: Decreasing the emissions of organic acid vapors in church organ environments

Acetic and formic acid vapors emitted from woodwork in historical organs are very important corrosive agents for lead pipes. These acids are slowly released from the wood both during playing and when the pipes are silent. To inhibit this emission process, the wood surface can be modified, by creating a protective layer with alkaline features. However, a coating of wood is not recommended since this could modify the appearance and create a layer not perfectly compatible with the substrate. For this reason, we propose to use some innovative nanotechnology that has been successfully applied for the deacidification of wood samples coming from the Vasa shipwreck. Application of calcium (or magnesium) hydroxide nanoparticles, with sizes ranging from 30–150 nm, allowed a homogeneous distribution of particles through the surface layer of wood simply by soaking (or spraying) it in a alcoholic (or mixed with less polar solvents) dispersion of nanoparticles. Nanoparticles do not modify the wood appearance and distribute randomly within the first layers of wood. The small size of particles accounts for the high reactivity with CO₂ from the air, to give the alkaline reserve of carbonates that provide high efficacy in the neutralization of gaseous acids. The emission of volatile organic compounds (VOC) from the treated wood was determined by using an emission test cell, Field and Laboratory Emission Cell (FLEC). The results show that the emissions of acetic acid vapor from nanoparticles treated wood was very low (< 70 μg/m² h) during the first 13 month. In contrast, untreated wood emitted high concentrations of acetic acid vapor (200–400 μg/m² h).     

Comparison of hot-air and low-radiant pew heating systems on the distribution and transport of gaseous air pollutants in the mountain church of Rocca Pietore from artwork conservation points of view

The concentrations of CO₂, CO, formaldehyde (H₂CO) and water vapour were simultaneously monitored in various sections of a mountain church situated in the village of Rocca Pietore in the Italian Alps. The performance of a conventional, hot-air heating system and a novel design for heating the church, consisting of low-temperature heating elements, such as electrically heated pews and carpets, were compared for the supply, transport and removal of gases, the deposition and/or transformation of which may affect the preservation of displayed works of art. Experiments with sulphur hexafluoride (SF₆) tracer-gas showed a considerable influx of external air through the hot air carrier ducts of the old heating system, and also the leakage of the internal air mostly via the apertures of the doors. The ventilation rates for the total volume of the church with the hot-air heating system (on for 1.5 h), the new heating system (on for 2 h), and without heating were calculated to be 0.25, 0.18, and 0.13 h⁻¹, respectively. Without heating, a nearly homogeneous distribution of gases has been observed along both the horizontal and the vertical cross-sections of the church. Immediately after switching on the hot-air heating system, the levels of CO₂ and water vapour showed a sharp increase. After turning this system off, the levels of gases showed a slow fall and they developed a highly non-homogeneous spatial distribution indoors for many hours. In the upper region of the church, being airtight, higher concentrations of the pollutants could be detected. The low levels of CO and H₂CO, mostly originating from incense burning during services, were correlated to that of CO₂. The hot-air heating system has been proved to present a potential deterioration risk to artworks, as it increases the supply, transport and deposition probability of air pollutants. On the other hand, the novel, symmetrical heating system eliminates these undesirable effects, thus its application is advantageous to all churches involved in the preservation of works of art.     

The role of copper on colour of palaeo-Christian glass mosaic tesserae: An XAS study

This work reports mainly the results of an X-ray Absorption Spectroscopy (XAS) study carried out on coloured glass tesserae from the palaeo-Christian mosaic which decorated the votive chapel of St. Prosdocimus (Padova) until its replacement with the current frescoes of Renaissance age, and which is one of the only two known mosaics in the Veneto region (Italy). The study aims at clarifying how the different local structure, oxidation state and quantity of copper influenced colour. Analysis of high-resolution Cu-K edge X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectra showed that copper is present as cuprite (Cu₂O) in orange samples and as metallic copper in red and brown ones. These phases are responsible for both the colour and opacity of the samples. In addition, Cu¹⁺ ions linked to the oxygen atoms of the glass framework were identified in ratios of about 60% and 30% of total copper in orange and red/brown samples, respectively. In blue and green samples, copper is dispersed in the glass matrix as a mixture of Cu¹⁺ and Cu²⁺ ions, and no crystalline phases are visible. In this context, the Cu¹⁺ and Cu²⁺ contents in glass were also quantified thanks to suitable standards, demonstrating that, when Cu²⁺ is the main chromophorous ion, colour intensity is directly correlated to its content in the glass. In particular, in green and blue samples, coloured by copper, Cu²⁺ content varies from 26% to 56% of total copper, and the higher contents of Cu²⁺ are shown by more intensely coloured samples. It should be stressed here that the green colour of the analysed tesserae is given by the physical interaction of blue colour, due to Cu²⁺ ions, and yellow colour, due to Pb antimonates used as opacifiers.     

A new class of gels for the conservation of painted surfaces

The application of a new class of organogels as cleaning tools for painted surfaces is described. It combines some of the most attractive features of cleaning liquids and normal gels while diminishing the deleterious characteristics of both. Thus, the ‘latent’ gellant, polyethyleneimine (PEI), reacts with CO₂ at room temperature in solutions of several organic liquids to produce an ammonium carbamate form (PEICO₂). This charged species organizes itself into 3D polymer networks which immobilize the liquids as gels. The properties of the original solution (i.e. a free-flowing liquid) are re-established immediately after addition of a small amount of a weak acid which displaces the CO₂ molecules and makes the PEI chains positively charged. The visual changes are substantiated by rheological analyses. Results from analytical tests to determine the utility of these gels as cleaning tools for painted surfaces of historical and artistic interest, have been obtained from contact angle and FTIR measurements as well as visual comparisons of the surfaces before and after application of the gels. The analyses indicate that the PEICO₂-based organogels were very effective in removing different surface patinas from painted supports. A surface layer of dammar was completely removed from a test canvas with oil paint, an aged painting from the XIX century, and a XV century oil-on-wood panel attributed to Mariotto di Cristoforo. Finally, a surface acrylic polymeric resin (used in a restoration performed during the 1960s) was also successfully removed from Renaissance wall paintings decorating the Santa Maria della Scala Sacristy in Siena, Italy. The isothermally rheoreversible gel approach described in this work represents a new, highly versatile, and very efficient method for removing aged surface patinas from works of art.     

Environmental conditions controlling the chemical weathering of the Madara Horseman monument,NE Bulgaria

The conditions that led to the deterioration of the Madara Horseman sculpture, a relief carved in a sandy limestone cliff in north-east Bulgaria, were studied, with most emphasis on the chemical weathering at the stone–atmosphere interface. Total deposition sampled close to the monument contains high concentrations of NH₄⁺ and K⁺, which shows the influence of the dense vegetation in the area, and Ca²⁺, which reflects the cliffˈs weathering products. Ca²⁺ is also one of the most important constituents (next to aluminosilicates) of the atmospheric particulate collected at the monument. S-rich particles are the most abundant particles in the size range < 0.5 μm. High amounts of biogenic particles (K-P-S-rich) were found, especially for particles < 1.0 μm. The chemical, mineralogical and petrographic characteristics of the stratum that holds the monument were studied down to a depth of 20 cm. Two distinctive processes are active at the stone–atmosphere interface. Firstly, a weathering crust (ca. 2 mm thickness), consisting mainly of calcite and gypsum and enriched with Cl^–, K⁺ and NO₃^–, is formed in the rain-sheltered areas of the monument. Secondly, karstic dissolution in the interior of the rock substrate leads to the formation of a hard carbonate crust at the surface of the sculpture. This natural surface hardening leads to a state of ‘auto-conservationˈ of the monument. The atmospheric composition seems to have only a limited influence on the deterioration of the Madara Horseman. Far more important are the micro-climatic conditions and the action of lichens.     

Deacidification of paper using dispersions of Ca(OH)2 nanoparticles in isopropanol. Study of efficiency

The efficiency of a recently described non-aqueous method for paper deacidification using Ca(OH)₂ nanoparticles in isopropanol was evaluated by pH and colorimetric measurements and by the analysis of the degree of polymerization (DP). Samples of plain paper and paper with iron gall ink were tested. The results were compared with non treated samples and samples submitted to the traditional treatment with saturated aqueous Ca(OH)₂ solution. By comparing the two conservation methods, the aqueous one shows higher neutralization reaction kinetics than the non-aqueous one. The iron gall ink samples maintain their coloration closer to the original after the non-aqueous Ca(OH)₂ nanoparticles treatment, in contrary to the aqueous treatment that changes the ink aesthetics considerably. Artificial aging tests revealed a general increase in the aging stability of deacidified paper samples. The Ca(OH)₂ nanoparticles treatment can be an alternative for papers who can not be treated by the classical aqueous treatment, e.g. papers with water soluble components.     

Photoluminescence of the inorganic pigments Egyptian blue, Han blue and Han purple

The room-temperature photoluminescence spectra of various samples of Egyptian blue (CaCuSi₄O₁₀) are presented, discussed and compared with those of recently synthesized compounds corresponding to the ancient pigments Han blue (BaCuSi₄O₁₀) and Han purple (BaCuSi₂O₆). All the samples of Egyptian blue show identical spectra, in spite of their very different origin. The spectra of Han blue and Han purple are significantly different. Since the Cu²⁺ ion may be considered the only luminescent centre in the spectral range under investigation, the differences between the spectra of the various pigments are ascribed to a ligand-field change. This can be related to the larger size of the Ba²⁺ ion with respect to Ca²⁺. The use of PL spectra for the identification of these pigments in works of art is proposed.     

Preservation of aged paper using borax in alcohols and the supercritical carbon dioxide system

Selecting an appropriate paper deacidification agent is very important for the deacidification of paper. The use of three deacidification agents (i.e., iso-butylamine, calcium propionate, and borax) is studied for the deacidification of paper using the immersion treatment by investigating the paper surface pH, alkaline residue, paper whiteness, strength, and other performance indicators. Results show the deacidification by borax solution not only results in the promotion of a proper pH range, high level of alkali reserves, and ignorable influence to paper appearance, but also to the enhancement of the mechanical intensities of paper even after artificial aging. Supercritical carbon dioxide (CO₂SCF), as a solvent system, is used in the deacidification of acidic papers using the borax solution of water and alcohol. CO₂SCF improved the deacidification process by significantly improving the pH value and the base residual value. The borax in supercritical fluids can be better combined with cellulose hydroxyl to improve the mechanical properties of paper substantially. The treatment of borax in CO₂SCF could be an alternative for acidic papers. Aside from improving the pH and depositing a sufficient alkaline residual, CO₂SCF also strengthens the mechanical properties of treated papers.     

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.     

Painting technique and state of conservation of wall paintings at Qusayr Amra,Amman – Jordan

The state of conservation of the frescoes at Qusayr Amra was investigated by integrated physico-chemical measurements, particularly optical and scanning electron microscopy, μ-infrared spectroscopy, mass spectrometry and X-ray powder diffraction.The frescoes appear darkened and severely damaged owing to the deterioration of surface treatments and to the widespread presence of different salts. These caused significant detachments of the painting layers.The materials used in the painting and preparation layers and in the wall plaster were characterized in order to clarify the painting technique. Different pigments have been identified on the pictorial layers: the original ones correspond to green earth, yellow and red ochre, realgar, bone black and lapis lazuli and others, such as titanium white and cobalt blue, ascribed to recent restoration works. Proteinaceous materials (egg or yolk) have been identified as binders for the pigments, indicating a tempera painting technique.Three different products, belonging to restoration interventions, have been also identified: the natural product shellac, ascribable to next-to-last restoration and scarcely removed during last restoration also because of its insolubility, the synthetic vinyl acetate and acrylic polymers. Particularly the latter one indicates an on-going degradation of the applied fixatives.The extensive deterioration of the surfaces is also due to the widespread presence of salts, such as chloride, nitrate and sulphate clearly identified by XRD measurements.The obtained results give a comprehensive overview on the employed painting technique and its state of preservation and on the causes of the painting deterioration. Therefore, they are a fundamental tool to develop durable and compatible materials and methodologies for a future conservation strategy of this site.     

Investigation of the technology of historic mortars

Historical evidence on the use of mortars to meet several needs has existed for millennia. With reference to the characteristic historical periods of the city of Rhodes, mortar sampling was performed on historical constructions, masonry and architectural surfaces. In the present work the different mortar technologies are investigated aiming to answer questions regarding their finality, i.e. whether their differences arise mainly from the various historical periods of construction or from the purposes they had to serve, imparting to the mortars the properties required by their function in the structure. Mineralogical, chemical, physical and mechanical investigations have been performed on characteristic samples after gradation. The exponentially declining function of the ratio CO₂/H₂O structurally bound to the CO₂ content shows a continuous evolution of the kinetics governing the various mechanisms of carbonation of the binder or the formation of hydraulic components during setting, hardening and ageing of the mortars. The grouping of mortars in well-distinct ‘hydraulic levels’ is ascribed to the physico-chemical cohesion and adhesion bonds developed at the matrix and matrix/aggregate interfaces, respectively, allowing for the mortars to either bear continuous stresses and strains as joint mortars or provide compact impermeable renderings which harden even more on contact with water. Hence, parameters determining the diversification of the resulting mortar/matrix types concern the raw materials employed as binding materials and the production processing.     

Archaeomagnetic investigation of a metallurgical furnace in Pisa (Italy)

An archaeological excavation has been carried out at Pisa (Italy), unearthing an ancient metallurgical workshop. Since archaeological burnt materials provide important records of direction and intensity of the Earth's magnetic field in the past and they can be used to better improve geomagnetic secular variation curves (SVCs), an archaeomagnetic study has been performed. This small copper-alloy furnace presents a circular concave shape covered with a thin layer of mortar, with some traces of heated clay surrounding the feature that confirms the high temperature reached inside it. Archaeological context dating points to the last firing of the furnace between the last quarter of the 13th century and the first quarter of 14th century AD, when then the metallurgical workshop was transformed in a warehouse. Archaeomagnetic sampling has been performed using the modified Thellier method, by collecting several, large and independently oriented aliquots of heated clay, forming the bottom part of the circular wall of the structure. Laboratory treatments have been conducted at the IGG-CNR ARCHEO_LAB (Pisa, Italy) and at St. Maur Palaeomagnetic laboratory (Paris, France). Analytical measurements of the thermo-remanent magnetization index acquired from the samples have been performed using a large cell induction magnetometer for large samples, and the characteristic remanent magnetization (ChRM) has been successfully isolated after an alternate field demagnetization cleaning procedure for each sample. The final mean archaeomagnetic direction has been calculated at sampling site (D = 6.9°; I = 52.8°; N = 9; k = 305; α₉₅ = 2.6°) following the Fisher Statistics, and it exhibits a perfect agreement with some coeval already published directions obtained from Mt. Arso lava flows, these latter being an important anchor point in the preliminary Italian secular variation curve. Comparison with the preliminary Italian SVC, the French SVC and the SCHA.DIF.3K archaeomagnetic regional model have permitted to define an archaeomagnetic absolute age confirming the conventional archaeological age, underlining the importance of this result into the Italian archaeomagnetic data set.     

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.     

Electronic paramagnetic resonance as a tool for studying the blackening of Carrara marble due to irradiation by a Q-switched YAG laser

Several authors or practitioners have remarked that Q-switched lasers have an immediate blackening effect on mineral pigments such as vermilion (HgS), minium (Pb₃O₄), white lead [2PbCO₃. Pb(OH)₂], malachite [Cu₂CO₃.(OH)₂] and yellow ochre (FeOH₂). A similar blackening effect can also be obtained on veined Carrara marble. This stone contains several trace elements, particularly iron and manganese. The latter is responsible for a particular response in electronic paramagnetic resonance spectroscopy (EPRS). We investigated the effect of a Q-switched Nd:YAG laser irradiation on the EPRS trace of Carrara marble. Further experiments were performed with the same analytical tool on synthetic calcite powders that had been doped with iron or manganese. It appeared that no significant change of EPRS trace could be put into evidence after laser irradiation of both bulk Carrara marble or doped calcite powders, although some samples had actually blackened. It is concluded that the blackening effect is not due to an oxidation of manganese ions. Colour measurements were also performed within the framework of this investigation. They showed that the colour shift to black is proportional to the fluence applied to the stone surface     

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.     

The white colour in Etruscan polychromes on terracotta: Spectroscopic identification of kaolin

The present work reports on a spectroscopic study of white colour samples collected from Etruscan polychromes on terracotta from the Cerveteri area. In particular, both white-on-red potsherds of the Orientalising period and high-value polychromes of the Archaic period were considered. The white pigment, a fundamental element in this class of artworks, was not clearly identified in previous archaeological and analytical studies, although the use of kaolin was tentatively proposed. Therefore, samples from the Monte Sughereto kaolin quarry in the Cerveteri area were also studied. The results of detailed analyses carried out using micro-Raman spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy first show that the quarry material is a high-purity kaolin containing quartz. Raman results strongly suggest that the same kind of kaolin was employed in the polychromes of the Archaic period. As to white-on red potsherds, infrared results have a key role in showing that the white pigment is a kaolin closely corresponding to the quarry material since a particular kaolin polytype (dickite) is dominant in both cases. The present work thus provides the first definitive identification of the white pigment used in Etruscan polychromes on terracotta from the Cerveteri area, and suggests that the source of kaolin might be the Monte Sughereto quarry.