A non‐destructive characterization of stratigraphies in contemporary prints using micro‐Raman spectroscopy

Abstract

AbstractArtistic 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.