title: Preparation of thin-sections of painting fragments: classical and innovative strategies.
abstract: For more than a century, the analyses of painting fragments have been carried out mainly through the preparation of thick resin-embedded cross-sections. Taking into account the development of innovative micro-analytical imaging techniques, alternatives to this standard preparation method are considered. Consequently, dedicated efforts are required to develop preparation protocols limiting the risks of chemical interferences (solubilisation, reduction/oxidation or other reactions) which modify the sample during its preparation, as well as the risks of analytical interferences (overlap of detected signals coming from the sample and from materials used in the preparation). This study focuses particularly on the preparation of thin-sections (1-20 μm) for single or combined fourier transform infrared (FTIR) spectroscopy and X-ray 2D micro-analysis. A few strategies specially developed for the μFTIR analysis of painting cross-sections have already been reported and their potential extrapolation to the preparation of thin-sections is discussed. In addition, we propose two new specific methods: (i) the first is based on a free-embedding approach, ensuring a complete chemical and analytical neutrality. It is illustrated through application on polymeric design objects corpus; (ii) the second is based on a barrier coating approach which strengthens the sample and avoids the penetration of the resin into the sample. The barrier coating investigated is a silver chloride salt, an infrared transparent material, which remains malleable and soft after pellet compression, enabling microtoming. This last method was successfully applied to the preparation of a fragment from a gilded Chinese sculpture (15th C.) and was used to unravel a unique complex stratigraphy when combining μFTIR and μXRF.
authors.affiliation: European Synchrotron Radiation Facility, 6, rue Jules Horowitz, Grenoble F-38000, France. Electronic address: pouyet@esrf.fr.
authors.forename: Emeline
authors.initials: E
authors.lastname: Pouyet
authors.affiliation: Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Via G. Giusti 9, Firenze 50121, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Lluveras-Tenorio
authors.affiliation: Consiglio Nazionale delle Ricerche - Istituto di Fotonica e Nanotecnologie (CNR-IFN), Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano 20133, Italy.
authors.forename: Austin
authors.initials: A
authors.lastname: Nevin
authors.affiliation: Politecnico di Milano - Dipartimento di Chimica Materiali e Ingegneria Chimica, Piazza Leonardo da Vinci 26, Milano 20133, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Saviello
authors.affiliation: European Synchrotron Radiation Facility, 6, rue Jules Horowitz, Grenoble F-38000, France.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sette
authors.affiliation: European Synchrotron Radiation Facility, 6, rue Jules Horowitz, Grenoble F-38000, France; LAMS (Laboratoire d'Archéologie Moléculaire et Structurale) UMR-8220, 3 rue Galilée, Ivry-sur-Seine 94200, France.
authors.forename: Marine
authors.initials: M
authors.lastname: Cotte
keywords: Cultural heritage; Fourier transform infrared spectroscopy; Paintings; Sample preparation; Synchrotron