Cuprorivaite (CaCuSi(4)O(10), also known as Egyptian blue) exhibits an exceptionally high emission quantum efficiency in the near-infrared region (lambda(max) = 910 nm, Phi(EM) = 10.5%) and a long excited state lifetime (107 mus); these properties make it appealing for several applications in the fields of biomedical analysis, telecommunications and lasers.

The photo-induced luminescence properties of Egyptian blue, Han blue and Han purple were investigated by means of near-infrared digital imaging. These pigments emit infrared radiation when excited in the visible range. The emission can be recorded by means of a modified commercial digital camera equipped with suitable glass filters. A variety of visible light sources were investigated to test their ability to excite luminescence in the pigments. Light-emitting diodes, which do not emit stray infrared radiation, proved an excellent source for the excitation of luminescence in all three compounds. In general, the use of visible radiation emitters with low emission in the infrared range allowed the presence of the pigments to be determined and their distribution to be spatially resolved. This qualitative imaging technique can be easily applied in situ for a rapid characterisation of materials. The results were compared to those for Egyptian green and for historical and modern blue pigments. Examples of the application of the technique on polychrome works of art are presented.

The variations of the fluorescence emission of carmine lake travelling through an absorbing and scattering medium, such as a paint layer, were investigated by ultraviolet (UV)-visible absorption, fluorescence spectroscopy, and imaging techniques. Samples of the lake were studied in dilute and saturated solutions, on a reference test panel and a real case study. Relevant spectral modifications have been observed as a function of the lake concentration mainly consisting of a fluorescence quenching, red shift of emission maxima, and deformation of emission band. The application of a correction factor based on the Kubelka-Munk model allowed fluorescence spectra obtained in solution and on painted samples of known composition to be compared and correlated, highlighting that the fluorescence of the lake within paint layers is affected by both self-absorption and aggregation phenomena. This approach has been successfully applied on a painting by G. Vasari for the noninvasive identification of carmine lake. The results reported here emphasize the necessity of taking physical phenomena into account in the interpretation of the fluorescence spectra for a proper and reliable characterization and identification of painting materials in works of art.

Ultraviolet-induced fluorescence spectroscopy is a commonly used technique for the characterization and identification of painting materials, such as organic binders and colorants. Its interpretation is strictly connected to both the experimental setup and an understanding of the physical and chemical interactions among materials in paint layers, which are commonly composed of a fluorescent organic binder and a pigment. When irradiated with ultraviolet radiation, the light emitted by fluorophores present in the organic binder undergoes several types of interactions, in particular scattering and absorption by neighboring pigmented particles and auto-absorption. As a result of scattering and absorption phenomena, the emission spectrum is deformed according to the physical properties of the surrounding pigmented particles. This can lead to shifts of the emission maxima and/or to the formation of apparent new emission bands. The extent of the modifications to the emission spectra, caused by auto-absorption and selective absorption phenomena, may lead to the erroneous characterization or identification of the fluorescent materials. As a consequence, the interpretation of the emission signal can be greatly compromised. A correction based on the Kubelka-Munk theory is proposed to evaluate the extent of the spectral distortion and is assessed on modern replicas of wall paintings of known composition. Although the model cannot be applied to all cases, qualitative distinctions between real and apparent emissions are achieved.

The aim of this study is to develop a method for the non-invasive and in situ identification of organic binders in wall paintings by fiber optic mid-FTIR reflectance spectroscopy. The non-invasive point analysis methodology was set-up working on a wide set of wall painting replicas of known composition and using statistical multivariate methods, in particular principal component analysis (PCA), for the interpretation, understanding, and management of data acquired with reflectance mid-FTIR spectroscopy. Results show that PCA can be helpful in managing and preliminary sorting of the large amount of spectra typically collected during non-invasive measurement campaigns and highlight further avenues for research. The developed PCA model was finally applied to the case of a Renaissance wall painting by Perugino assessing it predictability as compared to the interpretation of the single spectrum.

The development of mining to acquire the best raw materials for producing stone tools represents a breakthrough in human technological and intellectual development. We present a new approach to studying the history of flint mining, using in situproduced cosmogenic 10 Be concentrations. We show that the raw material used to manufacture flint artifacts Ϸ300,000 years old from Qesem Cave (Israel) was most likely surface-collected or obtained from shallow quarries, whereas artifacts of the same period from Tabun Cave (Israel) were made of flint originating from layers 2 or more meters deep, possibly mined or quarried by humans.T he first archaeological evidence of the use of stone tools dates to Ϸ2.5 million years ago (1). In prehistory, one of the most widely used raw materials was flint, a microcrystalline form of quartz. Because flint quality varies, the choice of raw materials for producing tools is important; flint mined from underground is generally more easily workable than surface-collected material, which is not always present in large quantities and usually weathered by atmospheric agents (2, 3). There are only a few reports of flint mining sites in the early Paleolithic, such as the Acheulian complex at Isampur (India) (Ϸ1.0 million years B.P.), ¶ ¶ the Lower-Middle Paleolithic in Mount Pua (Israel) (Ϸ200,000 B.P.) (5), and the Middle Paleolithic in Qena (Egypt) (Ϸ50,000 B.P.) (6). The approach presented in this article can be used to directly analyze flint artifacts from different stratigraphic layers in prehistoric caves, leading to information on the provenance of the raw material. We show that the analysis can determine whether the raw material originated from deep layers (1 m or more), possibly mined by humans. The application of this method will contribute to our understanding of the history of flint mining in different regions of the world and can be expanded to other raw materials. Be in Situ Production in Flint MineralsThe interaction of showers of high-energy primary and secondary cosmic ray particles with the atmosphere and shallow matter in the earth's crust produces a number of long-lived cosmogenic isotopes by nuclear reactions (7,8). The cosmogenic isotope in situ buildup in rocks has been extensively studied both theoretically and experimentally by accelerator mass spectrometry methods of analysis (ref. 9 and references therein). In situ cosmogenic production was shown to involve a complex balance between various geophysical processes and parameters: (i) altitude-and latitude-dependent cosmic-ray particle fluxes; (ii) proton and neutron absorption coefficients in the earth's crust (the mean attenuation length for spallation reactions in rocks is about ⌳ Ϸ 160 g͞cm 2 , and the average rock density is ϭ 3 g͞cm 3 ); (iii) the erosion rate of surface rocks; (iv) the burial history of rocks; and (v) the production rate by slow (stopping) and fast muons, penetrating particles produced as secondary particles in the shower caused by cosmic particles. The case of cosmogenic 10 Be (T 1/2 ϭ 1.5 milli...

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X-ray fluorescence spectroscopy (XRF) plays an important role for elemental analysis in a wide range of scientific fields, especially in cultural heritage. XRF imaging, which uses a raster scan to...