On the stability of mediaeval inorganic pigments : a literature review of the effect of climate, material selection, biological activity, analysis and conservation treatments

This review is to be considered part of the development of the MEMORI dosimeter, to evaluate the impact of climate (relative humidity, temperature, illumination, etc., including volatile organic compounds) on moveable objects. In the framework of the MEMORI project, Ghent University was given the task to assess pigment degradation upon acetic acid exposure, and to collect information on pigments' stability. Moreover, to obtain a wider knowledge on the stability of common pigments, the effect of a variety of parameters was reviewed from literature. Discolouration and degradation of pigments significantly alter the legibility of polychrome works of art, so that the development of monitoring methods to ensure the preservation of cultural heritage objects is of primary importance

Initial results of finger imaging using Photoacoustic Computed Tomography

We present a photoacoustic computed tomography investigation on a healthy human finger, to image blood vessels with a focus on vascularity across the interphalangeal joints. The cross-sectional images were acquired using an imager specifically developed for this purpose. The images show rich detail of the digital blood vessels with diameters between 100 $\mu$m and 1.5 mm in various orientations and at various depths. Different vascular layers in the skin including the subpapillary plexus could also be visualized. Acoustic reflections on the finger bone of photoacoustic signals from skin were visible in sequential slice images along the finger except at the location of the joint gaps. Not unexpectedly, the healthy synovial membrane at the joint gaps was not detected due to its small size and normal vascularization. Future research will concentrate on studying digits afflicted with rheumatoid arthritis to detect the inflamed synovium with its heightened vascularization, whose characteristics are potential markers for disease activity.Comment: 2 figure

Tryptic peptide analysis of protein binders in works of art by liquid chromatography–tandem mass spectrometry

Comprehension of the materials, such as binding media, used by artists is of uttermost importance in restoration and in art historical studies. The most frequently used binders are drying oils and proteins; in this study focus is placed on proteins. Most actual methods for protein binder identification are based on complete hydrolyzation of the protein matter into its amino acids and separation/detection with gas chromatography – mass spectrometry (GC-MS) or high performance liquid chromatography (HPLC) after derivatization. Because amino acids itself are not characteristic for a protein, identification is often based on the relative amount of 7 stable amino acids. In the current study a proteomics approach was used, in which the proteins were digested enzymatically into peptides using trypsin before being separated and detected by liquid chromatography – electronspray ionisation tandem mass spectrometry (LC-ESI-MS/MS). Mascot (Matrix Science) was used to analyze the resulting data and for protein identification. This way, amino acid sequences could be studied that retain much more information about the proteins, their degradation and pigment-binder interactions. The protein content of homemade paint samples was extracted using different methods and analysed to select the best extraction strategy based on the number of peptides that were identified. A large dataset of 4 binders (animal glue, egg yolk, egg white and casein), mixed with 10 common pigments with different chemical properties was used to study the influence of pigments on the extraction method. Analytical characteristics of the selected method were determined. Finally the method was applied to historic paint samples. The results were compared with those obtained by traditional amino acid analysis methods

Characterization of Roman glass tesserae from the Coriglia excavation site (Italy) via energy-dispersive X-ray fluorescence spectrometry and Raman spectroscopy

The combined use of handheld energy-dispersive X-ray fluorescence spectrometry, Raman spectroscopy, and micro-energy-dispersive X-ray fluorescence spectrometry permitted the characterization of Roman glass tesserae excavation from the Coriglia (Italy) archeological site. Analyses of ten different glass colors were conducted as spot analyses on intact samples and as both spot analyses and line scans on select cross-sectioned samples. The elemental and molecular information gained from these spectral measurements allowed for the qualitative chemical characterization of the bulk glass, decolorants, opacifiers, and coloring agents. The use of an antimony opacifier in many of the samples supports the late Imperial phasing as determined through numismatic, fresco, ceramics, and architectural evidence. And dealinization of the exterior glass layers caused by the burial environment was confirmed