Ochres and earths: Matrix and chromophores characterization of 19th and 20th century artist materials Cristina Montagner a,b , Diogo Sanches a,b , Joana Pedroso a , Maria João Melo a,b , Márcia Vilarigues a,c,⇑ a Department of Conservation and Restauration, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus Caparica, 2829-516 Caparica, Portugal b REQUIMTE-CQFB, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus Caparica, 2829-516 Caparica, Portugal c VICARTE, Research Unit, Vidro e Cerâmica para as Artes, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus Caparica, 2829-516 Caparica, Portugal highlights " Ochre samples of 19th century brands: Winsor & Newton, Morin et Janet, Lefranc were analyzed. " l-FTIR allows to separate ochres with kaolinite, sulfate or quartz matrix. " The identification of the main chromophores was confirmed by Raman and l-XRD. " The matrix characterization allows to separate between synthetic and natural origin. " To clarified the nomenclature from the results a clustering system was proposed. graphical abstract article info Article history: Received 10 July 2012 Received in revised form 20 October 2012 Accepted 25 October 2012 Available online 21 November 2012 21 November 2012 Keywords: Ochre Fourier Transform Infrared Spectroscopy Raman microscopy abstract The present paper describes the main results obtained from the characterization of a wide range of nat- ural and synthetic ochre samples used in Portugal from the 19th to the 20th century, including powder and oil painting samples. The powder ochre samples came from several commercial distributors and from the collection of Joaquim Rodrigo (1912–1997), a leading Portuguese artist, particularly active during the sixties and seventies. The micro-samples of oil painting tubes came from the Museu Nacional de Arte Contemporânea-Museu do Chiado (National Museum of Contemporary Art-Chiado Museum) in Lisbon and were used by Columbano Bordalo Pinheiro (1857–1929), one of the most prominent naturalist Por- tuguese painters. These tubes were produced by the main 19th century colourmen: Winsor & Newton, Morin et Janet, Maison Merlin, and Lefranc. The samples have been studied using l-Fourier Transform Infrared Spectroscopy (l-FTIR), Raman microscopy, l-Energy Dispersive X-ray fluorescence (l-EDXRF), and X-ray diffraction (XRD). The analyzed ochres were found to be a mixture of several components: iron oxides and hydroxides in matrixes with kaolinite, gypsum and chalk. The results obtained allowed to identify and characterize the ochres according to their matrix and chromophores. The main chromophores where identified by Raman microscopy as being hematite, goethite and magnetite. The infrared analysis of the ochre samples allowed to divide them into groups, according to the composition of the matrix. It was possible to sepa- rate ochres containing kaolinite matrix and/or sulfate matrix from ochres where only iron oxides and/or hydroxides were detected. l-EDXRF and Raman were the best techniques to identify umber, since the presence of elements such as manganese is characteristic of these pigments. l-EDXRF also revealed the presence of significant amounts of arsenic in all Sienna tube paints. Ó 2012 Elsevier B.V. All rights reserved. 1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2012.10.064 ⇑ Corresponding author at: Department of Conservation and Restauration, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus Caparica, 2829-516 Caparica, Portugal. E-mail address: mgv@fct.unl.pt (M. Vilarigues). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 103 (2013) 409–416 Contents lists available at SciVerse ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa