Synchrotron UV−Visible Multispectral Luminescence Microimaging of Historical Samples

Abstract

UV-visible luminescence techniques are fre-quently used for the study of cultural heritage materials, despite their limitations for identification and discrimination in the case of complex heterogeneous materials. In contrast to tabletop setups, two methods based on the vacuum ultraviolet (VUV)-UV-visible emission generated at a bending magnet of a synchrotron source are described. The main advantages of the source are the extended wavelength range attained, the continuous tunability of the source, and its brightness, leading to a submicrometer lateral resolution. Raster-scanning microspectroscopy and full-field microimaging were implemented and tested at the DISCO beamline (synchrotron SOLEIL, France). Investigative measurements were performed on a sample from a varnished musical instrument and a paint sample containing the pigment zinc white (ZnO) in order to illustrate some of the challenges analyzing heterogeneous cultural heritage cross-section samples with the novel imaging approach. The data sets obtained proved useful for mapping organic materials at the submicrometer scale and visualizing heterogeneities of the semiconductor pigment material. We propose and discuss the combined use of raster-scanning microspectroscopy and full-field microimaging in an integrated analytical methodology. Synchrotron UV luminescence appears as a novel tool for identification of craftsmen's and artists' materials and techniques and to assess the condition of artifacts, from the precise identification and localization of luminescent materials.

Photoluminescence Properties of Zinc Oxide in Paints: A Study of the Effect of Self-Absorption and Passivation

“…18 Higher specific and reliable characteristics may be provided by the excitonic emission band, as already highlighted on model samples and real paintings. [19][20][21] Even though the exciton absorption onset is commonly utilized as a clue for the noninvasive identification of zinc white in nineteenth and twentieth century paintings, [22][23][24] the use of luminescence spectroscopy may offer high sensitivity in the case of complex mixtures of pigments.…”

Semi-automatic system for UV images analysis of historical musical instruments

“…If, on the one hand, the constituent material has a characteristic fluorescence color, on the other the possible effects of an aging could change the response, attenuating the brightness intensity. 5 Thus, any subsequent restoration and renovation interventions can therefore be easily discriminated. This is particularly evident in the musical instruments, since their use during the centuries has involved an irremediable wear that has led to a continuous maintenance and restoration.…”

Spectral Behavior of White Pigment Mixtures Using Reflectance, Ultraviolet—Fluorescence Spectroscopy, and Multispectral Imaging

“…For example, zinc white exhibits two fluorescence bands centered at 380 nm and 500 nm, respectively, but to our best knowledge no work has been published on the possibility for using these spectroscopic features as a fingerprint for the presence of zinc white in mixtures with other white pigments. 35,36 The aim of this work is to characterize the spectral behavior of white pigment mixtures in different binders (egg yolk and linseed oil) by means of nondestructive techniques in order to investigate the potentiality of UV-fluorescence spectroscopy, reflectance spectroscopy, and multispectral imaging for the identification of white pigments mixtures used as pictorial layers.…”