JOURNAL OF RAMAN SPECTROSCOPY J. Raman Spectrosc. 2007; 38: 1267–1273 Published online 12 June 2007 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/jrs.1759 A non-destructive characterization of stratigraphies in contemporary prints using micro-Raman spectroscopy A. Vila, 1 T. Jawhari 2 and J. F. Garc´ ıa 1* 1 Departament de Pintura, Facultat de Belles Arts, Universitat de Barcelona. C/Pau Gargallo 4, 08028 Barcelona, Spain 2 Serveis Cient´ ıfico-T ` ecnics, Universitat de Barcelona. C/Sol ´ e Sabaris 1, 08028 Barcelona, Spain Received 26 March 2007; Accepted 5 April 2007 Artistic prints are one of the most popular forms of art because their production process allows multiple reproduction of a single original. However, this characteristic has facilitated the introduction into the market of a huge number of forgeries and fakes, especially in reproductions of contemporary artists’ prints. Prints consist of an image stamped on a paper support. When different colours are involved in their composition, they are printed successively and the sequences appear registered in those small areas of the artwork where two colours overlap. In general, original prints are discriminated from forgeries and fakes mainly by stylistic criteria and, secondly, by their material composition. Nevertheless, in some cases this information is not enough to differentiate between original and non-original prints; therefore it would be helpful to establish the printing order of the different inks involved. The present study evaluates the capability of micro-Raman spectroscopy to establish the printing order of an artistic artwork. For this, the influence of instrumental instability and intrinsic print heterogeneity was first studied in order to define the number of replicate measurements required for a proper description of the composition of a print. Microscope lenses of different magnification were also used to evaluate the improvement in depth resolution when areas with overlapped inks were analysed. Thus, this article presents the Raman results obtained on prints in which inks with very similar (ultramarine and ocean blue) and very different (ocean and Prussian blue) Raman intensity signals appear overlapped. From these results, a procedure is proposed and applied to the study of the production process of a contemporary artist’s work. In all cases, the right printing order was established with a confidence level of up to 99%. Copyright  2007 John Wiley & Sons, Ltd. KEYWORDS: prints; stratigraphies; micro-Raman; inks; non-destructive procedure INTRODUCTION Prints are based on the production of multiple versions of an original design. Nowadays, the print run normally consists of a limited edition, and this information is recorded in pencil on the support, together with the artist’s signature. The print consists of an image stamped on a paper. Sticky ink is spread on a matrix on which the design had been done previously. Subsequently, this ink is transferred under pressure to the paper. When a coloured impression is made, each single colour is printed one after the other, and there are areas in which the different colours overlap. Because of the popularity of prints in the artistic market, a huge number of forgeries and fakes have appeared. While copies may not be misattributed or printed with the intention L Correspondence to: J. F. Garc´ ıa, Departament de Pintura, Facultat de Belles Arts, Universitat de Barcelona. C/Pau Gargallo 4, 08028 Barcelona, Spain. E-mail: jfgarcia@ub.edu to deceive, certainly frauds and fakes are sometimes made with such intention. The most widespread procedure for differentiating originals from forgeries is identification of the artistic style (described in the Catalogues Raisonn´ ees), 1–3 and sometimes the chemical composition of the constituent materials of the piece is also used. 4–6 In general, micro-Raman spectroscopy is a well- established, non-destructive technique widely used to char- acterize and identify materials in the cultural heritage field, 7–12 and the present study is a step forward in the application of this technique to that field. Complementing the chemical fingerprint, especially when the materials used are very common, would be of interest so as to establish the order in which the inks were printed. The methodology for extracting stratigraphic samples of the overlapped ink areas of prints is complicated and destructive, fundamentally because of the heterogeneity Copyright  2007 John Wiley & Sons, Ltd.