FT-IR, EPR and SEM-EDAX investigation of some accelerated aged painting binders

The results of FT-IR, SEM-EDAX and EPR investigations of some binders used in classical paintings and artificial aged binders, i.e. linseed oil, hen yolk and linseed oil/hen yolk are presented and discussed. Carbon dioxide, sulfur dioxide as well as nitrogen oxides were used as aging agents. Accordingly, the FT-IR spectra of all binders showed a set of characteristic modifications. This makes it possible to select the most representative bands which, acting as sui generis fingerprints, provided evidence of certain specific combinations for each binder and the polluting agents. The EPR spectroscopy was helpful in choosing the most appropriate chemical reactions whose products were identified in the corresponding FT-IR spectra. Moreover, the SEM-EDAX data allowed us to establish that, in the case of CO2 aging, the patina consists of finely dispersed carbon aggregates. Within this context, the most plausible chemical reactions explaining the observed changes were proposed and discussed.