Egyptian Blue Pigment Research Articles

Ancient Egyptian Blue (CaCuSi4O10) Pigment by Modern Solution Combustion Synthesis Method

<p class="Default"> </p><p class="Default"> The Egyptian blue pigment, CaCuSi<sub>4</sub>O<sub>10</sub>, has been used in ancient Egypt from 3000 BC. This pigment consists of CaCuSi<sub>4</sub>O<sub>10</sub> with variable amounts of wollastonite</p><p>(CaSiO<sub>3</sub>), high amount of Cu oxides, cuprite (Cu<sub>2</sub>O) or tenorite (CuO). It was prepared by melting the high percentage of copper in association with lime and desert sand in the Ancient time. In this work Egyptian blue was produced by solution combustion synthesis (SCS) in homogeneous aqueous solution of composition: cupper and calcium nitrates, sodium silicate and urea. This method permits chemically stable Egyptian blue fast and economic production. The Egyptian blue composition and structure obtained after SCS and calcination were studied by XRD, FTIR and SEM/EDX analysis. Crystallite size and crystal lattice parameters were calculated. An increase in combustion temperature during SHS and calcinations temperature influence Egyptian blue yield and crystallite size, slightly influence parameters of crystal lattice.</p>

Micronised Egyptian blue pigment: A novel near-infrared luminescent fingerprint dusting powder

In this paper we demonstrate that micronised Egyptian blue pigment can be used as a safe and simple material to visualise latent fingerprints on non-porous surfaces as near-infrared luminescent impressions. This allows the detection of latent fingerprints on highly patterned and reflective surfaces that have proven challenging with existing techniques.

Origin of the Anomalous Color of Egyptian and Han Blue Historical Pigments: Going beyond the Complex Approximation in Ligand Field Theory

The complex approximation is widely used in the framework of the Ligand Field Theory for explaining the optical properties of crystalline coordination compounds. Here, we show that there are essential features of these systems that cannot be understood with the usual approximation that only considers an isolated complex at the correct equilibrium geometry. We also show that a quantitative understanding of such optical transitions cannot, in general, be reached unless the internal electric field, ER(r), created by the whole crystal on active electrons confined in the complex, is also taken into consideration. Seeking to prove the key role played by this internal field, usually ignored in crystalline transition metal compounds, we focus on the origin of the color displayed by the Egyptian Blue pigment (CaCuSi4O10), the first ever synthesized by humans. This pigment, together with Han Blue (BaCuSi4O10), are chosen as model systems because the anisotropic ER(r) field produces huge shifts, up to ∼0.9 eV, in th...

The Two Non-Blue Amuns of the Shrine of Taharqa at Kawa*

The Twenty-fifth Dynasty Shrine of Taharqa at Kawa, currently residing in the Ashmolean Museum in Oxford, was tested for the presence of Egyptian blue pigment by using photo-induced luminescence. Two blue-skinned depictions of the Nubian god Amun-Re were discovered, as well as two non-blue-skinned depictions of the Theban version of the god. The choice not to paint the two Theban Amun-Res blue, as was the accepted practice during this period, is analysed and conclusions are drawn about Taharqa and other Nubian kings of the Twenty-fifth Dynasty. These conclusions have historic value because they offer insight into the actions and thoughts of the Nubian rulers, who would have been in control of declaring what iconography was acceptable. The conclusions were reached by taking into account the iconography of the shrine, the building projects of Taharqa, the evolution of the iconography of Amun-Re, and the symbolism of the colour blue in Egyptian art during this period.

Origin of the Exotic Blue Color of Copper-Containing Historical Pigments

The study of chemical factors that influence pigment coloring is a field of fundamental interest that is still dominated by many uncertainties. In this Article, we investigate, by means of ab initio calculations, the origin of the unusual bright blue color displayed by historical Egyptian Blue (CaCuSi4O10) and Han Blue (BaCuSi4O10) pigments that is surprisingly not found in other compounds like BaCuSi2O6 or CaCuO2 containing the same CuO4(6-) chromophore. We show that the differences in hue between these systems are controlled by a large red-shift (up to 7100 cm(-1)) produced by an electrostatic field created by a lattice over the CuO4(6-) chromophore from the energy of the 3z(2)-r(2) → x(2)-y(2) transition, a nonlocal phenomenon widely ignored in the realm of transition metal chemistry and strongly dependent upon the crystal structure. Along this line, we demonstrate that, although SiO4(4-) units are not involved in the chromophore itself, the introduction of sand to create CaCuSi4O10 plays a key role in obtaining the characteristic hue of the Egyptian Blue pigment. The results presented here demonstrate the opportunity for tuning the properties of a given chromophore by modifying the structure of the insulating lattice where it is located.

X-ray Diffraction and SEM Investigation of Wall Paintings Found in the Roman Temple Complex at Horvat Omrit, Israel

In the present study, the fragments of wall painting found in the Roman Temple Complex at Horvat Omrit were analysed for the first time using the non-destructive techniques of X-ray diffraction (XRD) and scanning electron microscopy (ESEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The application of these methods enabled unambiguous identifications of the pigments and plaster components of the samples. Quantitative information on mineral composition, crystallite size and elemental composition of each studied paint layer and plaster was collected. Based on the results of the XRD and EDS analyses, the green pigment was identified as celadonite. It was revealed that the Egyptian blue pigment does not contain impurities of tin and lead, and this excludes the use of bronze scrap in its synthesis. Comparison of the mineral composition of the paint layers indicates that a wider palette of colours was obtained by mixing the available mineral pigments. The study of cross-sections of painted specimens revealed the usage of slaked lime for plastering. The obtained results give a new insight into the wall painting technique employed by ancient artists at Horvat Omrit, in northern Israel.

Electrochemical Characterization of Egyptian Blue Pigment in Wall Paintings Using the Voltammetry of Microparticles Methodology

AbstractThe solid state voltammetric response of Egypt blue, Han blue and ploss blue pigments upon attachment to graphite electrodes in contact with aqueous phosphate buffer at pH 7.0 is studied by voltammetry of microparticles and scanning electrochemical microscopy. Such voltammetric responses, combined with those for synthetic specimens consisting of binary mixtures of the pigment and SiO2 or CaCO3 as well as ternary ones of CaCO3 and SiO2 mixtures allow for the identification of the pigment and the support in samples from wall paintings using different electrochemical parameters, in particular upon performing the Tafel and modified Tafel analysis of voltammetric peaks. Identification of Egypt blue in microsamples of murals from a Roman archaeological site in Castulo (Jaén, Spain) is discussed.

An Archer from the Palace of Nestor: A New Wall-Painting Fragment in the Chora Museum

The authors interpret two joining pieces of a brightly colored wall painting found at the Palace of Nestor in 1939. The fragment, removed from the walls of the palace prior to its final destruction, represents part of an archer, probably female. Alternative reconstructions are offered. Artistic methods and constituents of the plaster and paint are studied by XRD, PIXE-alpha analysis, XRF, SEM-EDS, PY/GC-MS, and GC-MS. Egyptian blue pigment was extensively employed. Egg was used as a binder for the pigments in a tempera, rather than a fresco, technique. The identification of individualized painting styles may make it possible to assign groups of wall paintings to particular artists or workshops.

The Blackening of Paint Containing Egyptian Blue

On ancient Egyptian artifacts, paint containing Egyptian blue pigment is often found to have become brownish green or even black. Darkened paints from several coffins have been investigated using gas-chromatography/mass-spectrometry (GC/MS) and other methods, to identify the cause of the discoloration. Different phenomena have been seen: one type of discoloration involved the browning of gum arabic throughout the paint layer; other examples showed surface discoloration in the varnish, the paint underneath being still bright blue. Surface dirt also contributes to darkening. Artificial aging of paints demonstrated that gum arabic binder can discolour sufficiently for paint to appear black. The poor hiding power and transparency of Egyptian blue contribute to the overall dark appearance.

THE EGYPTIAN GREEN PIGMENT: ITS MANUFACTURING PROCESS AND LINKS TO EGYPTIAN BLUE*

The chemical and structural analysis of raw Egyptian blue and green pigment cakes and of 50 pigment samples taken from paintings kept in the Louvre Museum was performed using a set of analytical techniques (X‐ray powder diffraction, transmission and scanning electron microscopy, Raman microscopy and UV spectrophotometry). The structural and morphological study of modern samples prepared on the basis of these results has provided technological data that help to explain ancient procedures. The role of the firing temperature, the atmospheric conditions in the furnace and the cooling rate are considered. The difference between Egyptian blue and Egyptian green pigment is proved. Manufacturing processes for their deliberate synthesis are proposed.