Ancient ‘gilded’ art objects from European cultural heritage: a review on different scales of characterization

Abstract

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.

Gold in the Alhambra: study of materials, technologies, and decay processes on decorative gilded plasterwork

“…The chemical characterization of gilding decorations is a complex task for conservation scientists. Samples are intrinsically heterogeneous at the microscale and are composed of mixtures of organic and inorganic materials that may have undergone chemical modifications and aging …”

From Archaeological Sites to Nanoscale: The Quest of Tailored Analytical Strategy and Modelling

“…For surface analyses, Atomic Force Microscope (AFM) is one of the techniques used by few studies (Crina Anca Sandu et al 2011), mainly dealing with the understanding of coatings like gilding or the assessment of protection properties for coatings protective treatments. This technique presents a lateral resolution, depending on the apex chosen for the surface probing, of about 10 nm.…”

IR Reflectography and Active Thermography on Artworks: The Added Value of the 1.5–3 µm Band

“…IR-C" thermography in the 7-14 µm band was also used to understand the nature of the support. Sandu et al provided a review centred on the characterization via NDT and micro-DT of artistic gilded objects for establishing the compositional, structural, morphological and physical-chemical parameters useful for monitoring the conservation state, behaviour and evolution in time of their aging/degradation/deterioration processes, the restoration treatments influencing the conservation state of the original materials and also for a rational choice of methods and materials of intervention, compatible with the original ones [10]. In 2012, a new imaging tool in art conservation called thermal quasi-reflectography (TQR) [11] was proposed and demonstrated.…”