Fig. 5

Sample 1. Fibres of different colours are visible in the micrographs taken with Spotlight 400 FT-IR microscope (a). ATR-FT-IR analysis of the dust, baseline and Kubelka–Munk correction applied (b)
Sample 1. Fibres of different colours are visible in the micrographs taken with Spotlight 400 FT-IR microscope (a). ATR-FT-IR analysis of the dust, baseline and Kubelka–Munk correction applied (b)