2014 JINST 9 C05006 PUBLISHED BY IOP PUBLISHING FOR SISSA MEDIALAB RECEIVED: December 13, 2013 REVISED: March 21, 2014 ACCEPTED: March 26, 2014 PUBLISHED: May 6, 2014 15 th I NTERNATIONAL WORKSHOP ON RADIATION I MAGING DETECTORS 23–27 J UNE 2013, PARIS,FRANCE GREG ´ ORIO LOPES painting workshop: characterization by X-ray based techniques. Analysis by EDXRF, μ -XRD and SEM-EDS V. Antunes, a,1 A. Candeias, b,d M.L. Carvalho, c M.J. Oliveira, b M. Manso, c A.I. Seruya, c J. Coroado, e L. Dias, d J. Mir ˜ ao, d S. Longelin c and V. Serr˜ ao a a Instituto Hist´ oria da Arte da Faculdade de Letras da Universidade de Lisboa (IHA-FLUL), Alameda da Universidade, 1600-214 Lisboa, Portugal b Laborat´ orio Jos´ e de Figueiredo / Direcc ¸˜ ao-Geral do Patrim´ onio Cultural (LJF-DGPC), Rua das Janelas Verdes 37, 1249-018 Lisboa, Portugal c Centro de F´ ısica At´ omica da Faculdade de Ciˆ encias da Universidade de Lisboa (CFA-FCUL), Av. Prof. Gama Pinto 2, 1649-003 Lisboa, Portugal d Laborat´ orio HERCULES, Universidade de ´ Evora, Largo Marquˆ es de Marialva 8, 7000-676 ´ Evora, Portugal e Instituto Polit´ ecnico de Tomar (IPT)/GeoBioTec ID&T unit, 2300-313 Tomar, Portugal E-mail: vanessahantunes@gmail.com ABSTRACT: Greg´ orio Lopes is one of the most famous Portuguese painters of the 15 th –16 th cen- turies. This work is a contribution to the study of his painting technique, specifically addressing the methodology used in the preparation of ground layers, which has never been carried out previously with this multianalytical method. For this purpose characterization of the ground layers of a selection of his paintings was car- ried out by micro-Energy Dispersive X-ray Fluorescence spectroscopy (μ -EDXRF), micro-X-ray Diffraction (μ -XRD), Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM- EDS) and complemented by micro-Raman spectroscopy. This work presents the results obtained on two altarpieces (c.1544) produced at the same period by this Portuguese artist. Ground layers are composed mainly of calcium sulfate — anhydrite and gypsum — and other compounds such as dolomite. Reference samples were prepared to obtain diffraction pattern of different percentage of gypsum and anhydrite and compared with the results from historical samples. KEYWORDS: X-ray fluorescence (XRF) systems; X-ray diffraction detectors 1 Corresponding author. c  2014 IOP Publishing Ltd and Sissa Medialab srl doi:10.1088/1748-0221/9/05/C05006