This paper presents a complementary analytical approach to characterize vegetable tanning materials
in historic leathers. It is described the application of two molecular spectroscopic techniques, ATR-FTIR
and UV-Vis, and three specific chemical tests to analyse tannins present in leathers. Acid butanol, nitrous
acid and rhodanine colorimetric tests, evaluated both visually and spectrophotometrically, were used
to identify condensed tannins, ellagitannins and gallotannins, respectively. Ten samples of commercial,
or laboratory prepared, vegetable tannins and seven new vegetable tanned leathers were also analysed
and obtained results were used for comparison. The complete analytical procedure was performed, in a
semi-micro-destructive scale, using fibres collected from leather. Analysis of ATR-FTIR and UV spectra of
commercial and laboratory prepared vegetable tannins allowed the establishment of the characteristic
bands of condensed and hydrolysable tannins and, more specifically, gallotannins. These data were used
to confirm the type of vegetable tanning agents used in new leather extracts. The same approach was
used in cultural heritage leathers, supported by the colorimetric tests, since protein degradation products
were co-extracted in aged leathers and interfered in IR spectra.