Pauline Martinetto

Making make-up in Ancient Egypt

The extensive use of green, white and black make-up has been known since the earliest periods of Egyptian history,. We have investigated cosmetic powders dating from between 2000 and 1200 BC that were preserved in their original containers. Quantitative crystallographic and chemical analysis of the organic and mineral components of the powders enabled us to identify two natural lead-based compounds: crushed ore of galena (PbS) and cerussite (PbCO3). We also found two unexpected constituents: laurionite (PbOHCl) and phosgenite (Pb2Cl2CO3). Because they are neither natural extracted ores nor products resulting from subsequent ageing or chemical modification, laurionite and phosgenite appear to be synthetic products manufactured by the Egyptians using ‘wet’ chemistry.

SYNTHESIS AND ACID RESISTANCE OF MAYA BLUE PIGMENT

Maya blue is an organo-clay artificial pigment composed of indigo and palygorskite. It was invented and frequently used in Mesoamerica in ancient times (eighth to 16th centuries). We analyse in this paper one of the characteristics of Maya blue that has attracted the attention of scientists since its rediscovery in 1931: its high stability against chemical aggression (acids, alkalis, solvents, etc.) and biodegradation, which has permitted the survival of many works of art for centuries in hostile environments, such as the tropical forest. We have reproduced the different methods proposed to produce a synthetic pigment with the characteristics of the ancient Maya blue. The stability of the pigments produced using either palygorskite or sepiolite has been analysed by performing acid attacks of different intensities. The results are analysed in terms of pigment decolouration and destruction of the clay lattice, revealed by X-ray diffraction. Palygorskite pigments are much more resistant than sepiolite pigments. It is shown that indigo does not protect the clay lattice against acid aggression. We show that Maya blue is an extremely resistant pigment, but it can be destroyed using very intense acid treatment under reflux.

Synchrotron X-ray micro-beam studies of ancient Egyptian make-up

Abstract Vases full of make-up are most often present in the burial furniture of Egyptian tombs dated from the pharaonic period. The powdered cosmetics made of isolated grains are analysed to identify their trace element signature. From this signature we identify the provenance of the mineral ingredients in the make-up and we observe different impurities in products, which have been demonstrated as synthetic substances by previous works. Focused X-ray micro-beam ( 2×5 μm 2 ) is successively tuned at 11 keV, below the LIII absorption edge of Pb, and 31.8 keV for global characterisation of the metal impurities. The fluorescence signal integrated over each single grain is detected against the X-ray micro-diffraction pattern collected in transmission with a bi-dimensional detector. Furthermore, for galena grains rich in Zn, the XANES signal at the K-absorption edge of Zn shows its immediate nearest-neighbour environment.

The effect of the octahedral cations on the dimensions of the palygorskite cell

Abstract High-resolution synchrotron X-ray diffraction recorded on a collection of palygorskites with different chemical compositions (obtained by analytical electron microscopy) permits unambiguous correlation of the crystallographic parameters a (or a sin β if a monoclinic phase is considered) with the nature of the octahedral sheet, i.e. with both the number of octahedral positions that are occupied and the type of octahedral cation. No significant changes in the lattice parameters b and c are observed. The unit cell modification consists essentially of an expansion in a as the number of cations with larger ionic radii (Mg2+ and Fe3+) predominates over smaller cations (Al3+). A linear dependency of a (or a sin β) on the chemical composition of the octahedral sheet was obtained that can be used for classifying palygorskite into compositional groups, using only conventional diffraction data, without the need for chemical analyses.

Synthesis and fading of eighteenth-century Prussian blue pigments: a combined study by spectroscopic and diffractive techniques using laboratory and synchrotron radiation sources

Prussian blue, a hydrated iron(III) hexacyanoferrate(II) complex, is a synthetic pigment discovered in Berlin in 1704. Because of both its highly intense color and its low cost, Prussian blue was widely used as a pigment in paintings until the 1970s. The early preparative methods were rapidly recognized as a contributory factor in the fading of the pigment, a fading already known by the mid-eighteenth century. Herein two typical eighteenth-century empirical recipes have been reproduced and the resulting pigment analyzed to better understand the reasons for this fading. X-ray absorption and Mössbauer spectroscopy indicated that the early syntheses lead to Prussian blue together with variable amounts of an undesirable iron(III) product. Pair distribution functional analysis confirmed the presence of nanocrystalline ferrihydrite, Fe10O14(OH)2, and also identified the presence of alumina hydrate, Al10O14(OH)2, with a particle size of ∼15 Å. Paint layers prepared from these pigments subjected to accelerated light exposure showed a tendency to turn green, a tendency that was often reported in eighteenth- and nineteenth-century books. The presence of particles of hydrous iron(III) oxides was also observed in a genuine eighteenth-century Prussian blue sample obtained from a polychrome sculpture.

Association of indigo with zeolites for improved color stabilization.

The durability of an organic color and its resistance against external chemical agents and exposure to light can be significantly enhanced by hybridizing the natural dye with a mineral. In search for stable natural pigments, the present work focuses on the association of indigo blue with several zeolitic matrices (LTA zeolite, mordenite, MFI zeolite). The manufacturing of the hybrid pigment is tested under varying oxidizing conditions, using Raman and ultraviolet–visible (UV-Vis) spectrometric techniques. Blending indigo with MFI is shown to yield the most stable composite in all of our artificial indigo pigments. In the absence of defects and substituted cations such as aluminum in the framework of the MFI zeolite matrix, we show that matching the pore size with the dimensions of the guest indigo molecule is the key factor. The evidence for the high color stability of indigo@MFI opens a new path for modeling the stability of indigo in various alumino-silicate substrates such as in the historical Maya Blue pigment.

A Synchrotron X-ray diffraction study of Egyptian cosmetics

This chapter draws attention to the synchrotron X-ray diffraction study of Egyptian cosmetics. Unguents, creams, powders and eye-paints were commonly used and kept in receptacles with characteristic shapes made of stone (alabaster, hematite, and marble), ceramic, wood, or reed. These receptacles had been placed in tombs as burial artefacts. Previous studies have shown that the make-up was used since the earlier periods (around 4000 EC for the pre-dynastic times) in relation to its aesthetic, hygienic, therapeutic, and religious functions. Their function is respectively to “clean” the gods face and to enable him to “see through Horuss eye.”These documents also describe the symbolic role that the ancient Egyptians attributed to cosmetics in maintaining cosmic order. The analysis of cosmetics as used in Ancient Egypt reveals the great variety of compositions using lead compounds along with chemical synthesis. This shows that 4000 years ago, people already wanted more impact from their use of cosmetics than simply highlighting of the eyes.

In situ dynamic analysis of solids or aqueous solutions undergoing chemical reactions by RBS or PIXE with external beams

Abstract Non-conventional applications of IBA techniques are under development on an external micro-beam line dedicated to the study of materials relevant to cultural heritage. Special set-ups have been designed to investigate the kinetics of materials transformation by dynamic (real-time) analysis using either RBS or PIXE. The first technique is well fitted to the study of the thermal oxidation of solids in air, whereas the second one is suitable for measuring the rate of elemental release in the liquid phase during solid–solution interaction. Preliminary tests have been performed to demonstrate the usefulness of this approach. On one hand we have applied dynamic micro-RBS to study the oxidation kinetics at 360 °C of pure copper and a copper–gold alloy and on the other hand we have checked the ability of micro-PIXE to measure in real time the release of lead in solution during the aqueous dissolution of lead containing glass or glaze.

Structure of Milled Galena (PbS) Particles as a Result of Grinding: Observations by Electron Microscopy

We have examined galena powders with the aim of providing information about the preparation mode of such powders from ancient Egyptian burial objects. Two extreme conditions of milling have been used to prepare galena powders in the laboratory, and the resulting products have been examined using scanning electron microscopy and transmission electron microscopy (TEM). The microstructure of hand-crushed coarse particles consists mainly of dislocation tangles. Annealing at 300 °C promotes a substantial recovery of the dislocation structure with the formation of subboundaries. Energetic ball milling produces a large variety of particle sizes, from 10 nm to several micrometers, with grains containing very high dislocation densities. Although PbS is a soft plastic compound, its fragmentation occurs down to very small sizes along various fracture regimes like in many brittle materials. Comparisons are made between TEM observations and the data obtained from x-ray diffraction peak profile analysis.

Identifying and quantifying amorphous and crystalline content in complex powdered samples: application to archaeological carbon blacks

Carbon black materials have been frequently used from prehistory as pigments for drawings and paintings and also as dyes, inks and cosmetics, since they are easy to make by burning organic matter. However, the carbonaceous phases they form are often ill-ordered and not easy to characterize. Five carbon black Roman micro samples found in vessels in houses in Pompeii were studied. These precious powders correspond to mixed phase samples that contain both crystalline and ill-ordered components. Here, a methodological approach that accomplishes the identification, quantification and mapping of the different phases in these heterogeneous samples using synchrotron-based techniques is proposed. The results were compared with those from scanning electron microscopy. Information about the nature of the mixtures and the origin of carbon black pigments is obtained. The use of charred vegetable materials is concluded, independently of the shape and the nature of the container.