X-RAY SPECTROMETRY X-Ray Spectrom. (In press) Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/xrs.930 In situ non-invasive EDXRF analysis to reconstruct stratigraphy and thickness of Renaissance pictorial multilayers † L. Bonizzoni, 1 * A. Galli, 2 G. Poldi 1 and M. Milazzo 1 1 Istituto di Fisica Generale Applicata, Universita’ degli Studi di Milano, via Celoria 16, 20133 Milano, Italy 2 CNR-INFM, Dipartimento di Scienza dei Materiali, Universita’ degli Studi di Milano-Bicocca, via R. Cozzi 53, 20125 Milano, Italy Received 6 July 2006; Revised 5 October 2006; Accepted 6 October 2006 In this paper, we report a few examples showing how energy dispersive XRF analysis (EDXRF) coupled with visible reflectance spectroscopy (vis-RS) can be successfully applied for the investigation of wood or canvas paintings by performing stratigraphic analyses with non-invasive techniques. The specific aim is to reconstruct layers and their thicknesses. The method has been tested in the laboratory on paint layers similar to traditional Renaissance ones. In situ analyses of a famous wood painting by Andrea Mantegna — ‘Madonna col bambino e un coro di cherubini’, Pinacoteca di Brera, Milan — were also carried out. While illustrating the results concerning the identification of pigments and the discrimination of layer stratigraphy, advantages and limitation of this method are pointed out. Copyright  2007 John Wiley & Sons, Ltd. INTRODUCTION The painting technique of fifteenth century Renaissance artists was based on laying down one to three different layers of pigments: the outermost of them is usually thin, the so-called velatura. The information on the artist’s palette can be achieved by a stratigraphic analysis, preferably with non-invasive techniques. The traditional method of stratigraphic analysis is, on the contrary, based on optical observation of the cross sections and it requires micro- sampling. The possibility of exploiting ion beam analyses (IBA), such as particle-induced x-ray emission (PIXE) 1–4 and particle-induced  -ray emission (PIGE), 5 has been recently considered, but in situ analyses are generally forbidden. We propose the combination of energy dispersive x-ray fluorescence (EDXRF) with visible reflectance spectroscopy (vis-RS), both achievable by portable instruments, the former used to detect chemical elements — and so deduce the related pigments—of the layer sequence down to the ground level, and the latter to detect only the pigments of the topmost layer. The identification of pigments in the topmost layer by reflectance spectra 6 makes it possible to infer the composition of the underlying layers. The additional importance of vis- RS is related to the possibility of detecting pigments made with light elements also, such as lapis lazuli and lakes, which XRF cannot identify. The possible use of the near infrared reflectance spectroscopy (NIR-RS) range allows the extension of RS analyses down to tens of microns of thickness. L Correspondence to: L. Bonizzoni, Istituto di Fisica Generale Applicata, Universita’ degli Studi di Milano, via Celoria 16, 20133 Milano, Italy. E-mail: letizia.bonizzoni@mi.infn.it † paper presented as part of a Special Issue of Papers from the 2006 European X-ray Spectrometry Conference, Paris, France, 19–23 June, Part 1. The zones to be investigated by our method are selected with infrared reflectography (from 0.8 to 1.1 μm), which allows distinguishing restored areas from the original ones. At the same time, infrared reflectography gives some additional information on paint materials. Our method was tested on a set of 20 paint layers of different compositions, according to published cross- sectional data. We used monolayers of a coloured pigment, pure or mixed with lead white; monolayers of mixed coloured pigments; multiple layers of coloured pigments, used alone or mixed with lead white; and multiple layers of mixed pigments. Pigments were bound in oil or in an egg tempera medium. The method allows the determination of layer sequence as well as the estimation of the average thickness of each layer. As example of in situ application we studied a panel painting by Andrea Mantegna (1431 – 1506), the ‘Madonna col bambino e un coro di cherubini’ (around 1485) of Pinacoteca di Brera, Milan. EXPERIMENTAL Both laboratory tests and in-field analyses were performed with a portable EDXRF spectrometer (Assing Lithos 3000) equipped with a low-power x-ray tube with a Mo anode and a Peltier-cooled Si-PIN detector. A Zr transmission filter between the x-ray tube and the sample guaranteed monochromatic radiation at Mo K˛ energy (E D 17.4 keV), with a 4 mm diameter collimator. The irradiated area on the sample was about 59 mm 2 . The distance between the sample and the x-ray tube was 1.4 cm; the same applies for the distance between the sample and the detector. The working conditions were 25 kV and 0.3 mA, with an acquisition time Copyright  2007 John Wiley & Sons, Ltd.