This paper is a review on the studies performed through imaging and spectroscopy-based analytical methods on ancient 'gilded' art-objects (9th-19th centuries) from the European cultural heritage.The review takes into consideration the gilded surfaces in polychrome art objects (easel and mural paintings, polychrome wooden objects, gilt leather and parchment), thus meaning the materials and techniques of application of gold or its imitations (silver, copper leaves, other metal alloys) from technical, analytical and conservation points of view.The characterization of artistic gilded objects is important for establishing the compositional, structural, morphological and physical-chemical parameters useful for monitoring the conservation state, behavior and evolution in time of their aging/degradation/deterioration processes, the restoration treatments (cleaning, consolidation, retouching, varnishing) influence on the conservation state of the original materials and also for a rationale choice of methods and materials of intervention, compatible with the original ones.The analytical approach has, as main requirement, to be noninvasive and non-or microdestructive, therefore, sampling is to be avoided or reduced to a minimum. A wide range of imaging and spectroscopy-based techniques is nowadays available from optical microscopy, UV fluorescence photography, IR reflectography, X-radiography, thermography, to scanning/transmission/environmental electron microscopy (SEM/TEM, E-SEM), atomic force microscopy (AFM), FTIR and Raman microscopy (micro-FTIR, micro-Raman), X-ray spectrometry (WDXRF/EDXRF/TXRF, XPS), Ion Beam Analyses (PIXE/PIGE, RBS, SR), etc. The most reliable and complete information can be obtained from an integrated, complementary and interdisciplinary approach, but microscopy still remains one of the most used and efficient tools in the characterization of gilding materials and their application techniques.

The degradation of cadmium sulfide (CdS)–based oil paints is a phenomenon potentially threatening the iconic painting The Scream (ca. 1910) by Edvard Munch (Munch Museum, Oslo) that is still poorly understood. Here, we provide evidence for the presence of cadmium sulfate and sulfites as alteration products of the original CdS-based paint and explore the external circumstances and internal factors causing this transformation. Macroscale in situ noninvasive spectroscopy studies of the painting in combination with synchrotron-radiation x-ray microspectroscopy investigations of a microsample and artificially aged mock-ups show that moisture and mobile chlorine compounds are key factors for promoting the oxidation of CdS, while light (photodegradation) plays a less important role. Furthermore, under exposure to humidity, parallel/secondary reactions involving dissolution, migration through the paint, and recrystallization of water-soluble phases of the paint are associated with the formation of cadmium sulfates.

This article presents an integrated approach for the authentication of five Russian icons through the study of their paint materials (elemental composition and stratigraphic mapping), state of conservation and artistic technique. The results of the applied analytical protocol, involving optical and scanning electron microscopy coupled with energy-dispersive X-ray spectrometry and Fourier transformed infrared spectroscopy/microspectroscopy, led to the conclusion that the five icons belong to the same group and iconographic school (from Northern Russia) and date from the end of the 16th century to the beginning of 17th century. Because of massive overpainting, the icons ''suffered'' a change in iconographic style and significance, and restoration treatment brought to light the original painting and its attribution. Identification of the composition of the original chromatic palette used by the iconographer, the stratigraphic mapping and the conservation state of the painting materials, along with the features of the original artistic technique, furnished key elements for the icons' authentication. Here, we present the first experimental data concerning the identification of the authentication characteristics, being part of a large project that has as its final aim the evaluation of the effectiveness and effects of the cleaning agent on the paint layers. Microsc. Res. Tech. 72:755-765, 2009. V