Different Fourier transform infrared microspectroscopic techniques, using attenuated total reflection (ATR) mode and single-element mercury-cadmium-telluride (MCT) detector (mapping) or multielement MCT detector (raster scanning), are compared with each other for the characterisation of inorganic compounds and organic substances in paint cross sections. All measurements have been performed on paint cross sections embedded in potassium bromide, a transparent salt in the mid-infrared region, in order to better identify the organic materials without the interference of the usual embedding resin. The limitations and advantages of the different techniques are presented in terms of spatial resolution, data quality and chemical information achieved. For all techniques, the chemical information obtained is found to be nearly identical. However, ATR mapping performed with a recently developed instrumentation shows the best results in terms of spectral quality and spatial resolution. In fact, thin organic layers (approximately 10 microm) have been not only identified but also accurately located. This paper also highlights the recent introduction of multielement detectors, which may represent a good compromise between mapping and imaging systems.

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Time of flight secondary ion mass spectrometry (ToF-SIMS) has become a fundamental analytical technique in cultural heritage studies to obtain the identification and distribution of organic components present in artworks. A sample taken from the soldier's golden shield decoration in the fresco Vela della Castità (San Francesco Lower Basilica, Assisi) was studied. The metal leaves for gilding decoration on wall paintings are usually applied using an oil-resin mordant as adhesive. In this work, organic and inorganic compounds used in this peculiar painting technique were identified by ToF-SIMS technique. High mass resolution spectrometry was applied for the chemical characterization of organic materials present in oil-resin binding media and red lake paint layer. Presence of azelaic, palmitic and stearic acids proved the nature of the oil binder between plaster and tin leaf and between tin and gold leaf. The analyses revealed also the presence of colophony, a natural resin used as an adhesive in this painting technique. Furthermore, the fresco cross section was studied using ToF-SIMS imaging. ToF-SIMS results agree with and are complementary to those obtained by other analytical techniques: scanning electron microscopy with X-ray microanalysis and Fourier transform infrared spectroscopy.

SummaryPyrolysis coupled with gas chromatography and mass spectrometry (Py/GC/MS) is a useful technique for the rapid characterisation of synthetic polymers. Many papers have been published about the application of this technique to industrial plastics and gums, but little attention has been focused on the characterisation of such group of synthetic compounds used in the artistic field. In this work pyrolysis is applied to the characterisation of consolidants and protectives used in the past restoration operations on Giotto's frescoes at the Scroveg ni Chapel, Padova.