Methodology for infrared spectroscopy analysis of sandwich multilayer samples of historical materials

Introduction Multilayer materials of cultural heritage such as historical materials and artwork are analysed as cross-section samples using microscopy and FTIR microscopy. Most commonly, these samples are embedded in synthetic resin, ground and polished. During this process, there is a high potential for the synthetic resin to contaminate the sample. The resin penetrates into the open pores or cracks in the sample, or solvent of the resin can partially dissolve some layer of the analysed sample. In both cases, the presence of synthetic resin significantly distorts the results of analysis, particularly the analysis of peripheral layers, which are of course the most contaminated. Interpretation of the FTIR spectra of individual layers is very difficult; it can be ambiguous and largely subjective. Moreover, analysed layers are usually a mixture of substances, where the studied substance (for example organic binder) is present as a minor component.