Laser removal of foxing from the pages of books and paper documents

Subject of study. This work was devoted to the removal of foxing spots from the pages of books and paper documents. Aim of study. The aim was to determine the output parameters of lasers that would allow the effective and safe removal of foxing. Method. Pulsed lasers were used in the experiments: a solid-state Nd:YAG laser with a wavelength of 0.53 mu m and an excimer ArF laser with a wavelength of 0.193 mu m. Main results. The highest foxing removal efficiency was achieved when the ArF laser was used for the treatment. The best results were achieved when using wet laser treatment in the case of paper containing wood pulp fibers and dry treatment for paper containing wood pulp. The optimal output characteristics of the ArF laser, which effectively removed foxing spots, included an energy density of 0.21-0.34 J/cm2, pulse repetition rate of 1-2 Hz, and pulse duration of 10 ns. A technique for quantifying the foxing removal effectiveness based on an analysis of digital optical images of the studied section of a book or document before and after laser treatment was proposed and experimentally verified. This technique is easy to use and does not require expensive analytical equipment. The research showed the high efficiency of foxing laser removal from the long-term perspective. Practical significance. The results obtained in this study showed the advantage of the laser treatment of books and paper documents with foxing spots compared with traditional restoration methods and recommend this technology for practical restoration work in libraries and archives. (c) 2024 Optica Publishing Group