Fig. 7
ATR-FTIR spectra of ink-free parchment areas in LIG specimens at various ageing times. a Entire spectral region; b Amide I and II regions; c peak fitting of the amide I and II region from spectra collected from unaged specimen; d peak fitting of the amide I and II region in aged specimen (32 days). Spectra color in a and b: black: reference (unaged specimen); red: 2 days; green: 4 days; blue: 8 days; purple: 16 days; cyan: 32 days and orange (D): difference spectrum between 32 days ageing and reference. All spectra in absorbance mode; normalized to the amide I (1650–1630 cm−1). Peak fitting curves in c and d marked with w denote the water component; cyan curves correspond to the second derivative