LASER STAIN REMOVAL OF FUNGUS-INDUCED STAINS FROM PAPER
HANNA MARIA SZCZEPANOWSKA, & WILLIAM R. MOOMAW
This work demonstrates that laser stain removal has significant advantages for removing stains from artwork on paper. When carried out at appropriate power levels, the laser-cleaned areas appeared indistinguishable from untreated, stain-free sections of the paper. We did not test the mechanical properties of the paper after exposure to the laser, but there was no effect on the appearance of the fibers and their arrangement. Examination of the fibers under high magnification substantiates the lack of damage. Because visible light rather than ultraviolet light is used, there is little risk that photo-induced aging will occur from laser treatment.
Based on these experiments, it should be possible to clean 1 sq cm of stain in a minute or two, provided that an effective mechanism for systematically positioning the beam on the artwork is employed to ensure complete coverage. While we have examined specifically stains caused by fungi, there is no reason why LSR would not be effective in removing other disfiguring stains as well. An added, unanticipated benefit of this technique is its capability of removing the fungal bodies or mycelium of some species without causing damage to the cellulose fibers of the paper. The basic mechanism by which the process works appears to be well enough understood that it should be possible to optimize the technique for a number of stain removal applications. A wide variety of pulsed lasers are available that cover the entire visible spectrum. Since the technology continues to evolve, it is best to consult a laser specialist or manufacturer about the most appropriate laser for a given application.