Laser cleaning of historical paper documents and diagnostics by means of LIF technique

Results of paper cleaning by means of the 532 nm Nd:YAG laser (pulse length 6 ns, fluency 0.3-0.6 J/cm2) are reported and discussed. Results of the surface cleaning of the paper samples originating among others from the two oldest Polish Bibles (XVI c.) are examined by the SEM technique after laser processing. For the process diagnostic the LIF spectra of paper samples recorded under excitation at 266 nm and 532 nm before and after processing are analysed and spectra of the non-contaminated samples are taken for reference. The presence of contamination and also cleaning history is evidenced in the recorded spectra. Comparison of SEM images and also the spectral characteristics of the originally contaminated samples before and after laser treatment confirm results of the laser cleaning.