shows FTIR DRIFT spectra of unmodified sample and sample, modified by Bookkeeper, stored for 5 days at 80 °C and relative humidity of 81% together with the differential spectrum obtained after mathematical subtraction of these spectra. The peaks at 2900 cm−1 (CH2 stretch), 1431 cm−1 (CH2 bending), 1375 cm−1 (the last two generally used for the sample crystallinity determination and monitoring), 1174 and 1123 cm−1 (CO stretching and CC stretching) are the characteristic peaks of cellulose-containing sample. Band at 1509 cm−1 origins from phenyls ring vibrations of lignins present in the sample