Egg yolk identification and aging in mixed paint binding media by NMR spectroscopy.

NMR spectroscopy is a powerful analytical tool for the identification and quantitative analysis of organic materials in a cultural heritage context. In this report, we present an analytical NMR protocol for the identification and semiquantification of egg yolk binders and mixed binding media that also contain a drying oil, namely linseed oil. The samples studied have been artificially and/or naturally aged in order to simulate the composition of organic materials in paintings. Analysis of the 1D and 2D NMR spectra showed that egg yolk can be identified even in binding media of considerable age via signals originating from cholesterol and/or cholesterol oxidation products present in the aged binding medium. Based on cholesterol-related and other lipid signals in the NMR spectra of egg yolk binders, a molecular marker (R/F) that suggests the presence of egg yolk in paint binders is proposed. Via this marker, the presence of egg yolk in the organic material obtained from an early 18th century Greek icon is confirmed, and this is further verified by 2D NMR spectroscopy. It is demonstrated that NMR molecular markers developed to estimate the hydrolysis/oxidation state of oil paintings are also suitable for the analysis of egg yolk and mixed medium (egg yolk-linseed oil) binders, indicating the generality of the NMR methodological approach in the analysis of organic materials in a cultural heritage context.

Fully-Non-Contact Masking-Based Holography Inspection on Dimensionally Responsive Artwork Materials.

Environmental control in galleries and museums is a necessity and is informed by the knowledge of ongoing processes of deterioration which can threaten the integrity and stability of artworks. Invisible dimensional changes in many works of art occur following environmental fluctuations as materials respond to the changes in humidity and temperature. The constant influence of dimensional changes usually remains invisible until displacement generates visible deterioration and irreversible damage. This paper exploits fully non contact coherent interferometry in a sequential masking procedure for visualising and studying surface deformation which is the direct effect of dimensional alterations induced by humidity changes. Surface deformation during dimensional displacements of constituent materials may occur on any artwork within an unstable environment. In this context, the presented research study explores the diagnostic potential of fully non contact sensors for the direct structural assessment of environmental effects as they occur in real time on works of art. The method is employed to characterise material responses, complementing and improving understanding of material behaviour in unstable environments.

The contribution of gas chromatography to the resynthesis of the post-Byzantine artist's technique.

Gas chromatographic analysis of ethyl chloroformate derivatives of samples taken from the paint layers of post-Byzantine panel paintings permitted the successful characterisation of the different binding media used in them. This paper describes an analytical study of various post-Byzantine binding media such as egg yolk and egg/oil emulsion, using gas chromatography. The characterisation of these icons' binding media is an important task, as it contributes to our understanding of and the reconstruction of the post-Byzantine artists' palette. It also enables us to investigate the validity of our assumptions about the influences of Venetian style on Greek icon painting techniques from the sixteenth to the early nineteenth century, which up to now have been based on information in artists' handbooks. The methodology involves two experimental steps: (1) hydrolysis of the proteins and triglycerides in the binding media to obtain free amino acids and fatty acids, and (2) the formation of ethyl chloroformate derivatives via derivatization with ethyl chloroformate (ECF). This methodology is of considerable interest, since it permits the identifcation of the nature of the proteinaceous binders used in these works through the simultaneous derivatization and determination of amino acids and fatty acids. Advantages of this methodology include the small quantity of sample required and the minimum preparation time involved. The proteinaceous media can be determined based on the ratios of seven stable amino acids, while the type of emulsions and drying oils used can be determined from the fatty acid ratio.

Analysis of post-Byzantine icons from the Church of the Assumption in Cephalonia, Ionian Islands, Greece: a multi-method approach.

A multi-method approach has been developed for the characterisation of the proteinaceous binding media, drying oils and pigments present in samples from the panel paintings of the Church of the Assumption in Cephalonia (Ionian Islands, Greece). The analytical protocol involved the use of scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX), Raman spectroscopy and gas chromatography. The identification of the pigments was achieved by SEM/EDX and Raman spectroscopy. The latter technique was also used for the detection of the binding media, while their characterisation was achieved by gas chromatographic analysis of ethyl chloroformate derivatives. The aim of this multi-method protocol was to obtain as much information as possible from the panel paintings of the Church of the Assumption, through non-destructive methods, before proceeding to gas chromatography. Little scientific information is available for the understanding of the construction technique and the materials used by the post-Byzantine artists and whatever is available comes mainly from artists' manuals. One of the aims of this paper is to provide a scientific background to the technology of the Ionian post-Byzantine icons.