Fig. 8
ATR-FTIR spectra of inked areas in gum arabic-free LIG specimens at various ageing times. a Full spectra; b amide I and II regions; c peak fitting of the amide I and II region in unaged specimen; d peak fitting of the amide I and II region in aged specimen (4 days); e 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: difference spectrum between 32 days ageing and reference; brown (D1): difference spectrum between inked and ink-free areas (both of unaged specimen) and orange (D2): difference spectrum between 32 days aged and reference specimens (both inked areas). All spectra in absorbance mode; normalized to the Amide I band (1650–1630 cm−1). Peak fitting curves in c, d and e marked with w denote the water component; cyan curves correspond to the second derivative