Testing of chemical composition of sealer samples on historical gold plating

The tests were made as based on analysis of absorptive spectra of varnish samples in infrared conditions. On the presented figure there are visible wide strands from OH, NH, CH, CH2 and CH3 (2840-2940 cm-1) group stretching vibrations (3300-3500 cm-1), CH, CH2 and CH3 (2840-2940 cm-1). Within the area of 1570-1660 cm-1 there are strands typical of scissoring vibrations of NH2 (amines) group and there are also strands from CN stretching bonds both in aliphatic chains (1158 cm-1) and in aromatic groups (1375 cm-1). Within the area of low wavenumbers there is a visible strands typical of bending vibrations of NH bonds. The sample also shows a strong 1722 cm-1 strand from C=O group. The presence of strong strands from ammonium compounds, which, in the process of polycondensate, create aminoplasts with simultaneous absence of strands originating from (CH2)2CO urea monomer, which indicates absence of contemporary protective varnishes based on urea and proves the historical (original) origin of the tested sealer samples.