Report on session “Cleaning of organic materials: paper, parchment, textile, wood”

Abstract

The general development in laser conservation has led to the observation that scientific approaches and diagnostics have been introduced as never before in this traditional discipline. The contributions of the laser cleaning on organic materials comprised celluloseand protein-based fibrous matter. These materials represent the most sensitive objects which laser cleaning has to deal with. Therefore, the highest input of scientific knowledge and advanced diagnostic tools are required from all disciplines of laser cleaning. The most important and ubiquitous artefact in this context is certainly paper. Consequently, most of the contributions were concerned with it. The research groups in Ljubljana, Slovenia (J. Kolar et al.) and Berlin, Germany (Kautek et al. “Interaction of laser light with soiled paper”) gave insight into a joint systematic investigation in the problem of laser interaction with soiled paper, which led to discoloration, in particular “yellowing”, under several circumstances. It was shown that this phenomenon is also an issue in other disciplines of laser cleaning (such as that of stone). However, the mechanisms involved are different. They are under thorough investigation. Poster contributions documented that paper is also a recent matter of interest with other European groups in Gdansk, Poland (G. Sliwinski et al., “Experimental investigations of stained paper documents cleaned by Nd:YAG laser pulses”) and in Simancas, Spain (C. Perez et al., “Positive findings for the use of laser in the cleaning of cellulose based supports”). In all these reports, microscopy and colour metrics turned out to be most valuable. Chemical essays such as FTIR spectroscopy have been repeatedly proposed, but need proper evaluation in order to give any meaningful information on the shallow zones of chemical modifications. On the other hand, X-ray techniques (XRD) of the crystalline components of cellulose seem to be too insensitive for possible changes (comp. the poster by C. Perez et al.). Laser-induced plasma spectroscopy (LIPS) has been reported in analogy to work with e.g. stone (C. Perez et al., and G. Sliwinski et al.). This technique definitely is an irreversible destructive method that should actually not be applied any more on any bioorganic fibre artefacts such as paper, parchment, and textiles. A preview poster on “Paper restoration using laser technology: a new European shared-cost project” by the collaborating groups in Berlin, Germany (W. Kautek et al.), at Heraklion, Greece (C. Balas et al.), at Hengelo, The Netherlands (R. Teule et al.), in Delft, The Netherlands (J.B.G.A. Havermans et al.), and other research partners in the Netherlands gave a concise review on the achieved findings of the EUREKA project “LACLEPA—laser cleaning of paper and parchment”. A cornerstone in the practical work of paper and parchment restoration will be the further optimization of a novel laser cleaning system specifically tailored for this purpose by the Berlin group (W. Kautek et al.) recently. It has been set up recently there, and allows precise, fast, electronically automatized restoration work without the common need of obnoxious safety equipment such as eye goggles. The European project will focus on the perfection of this system by the implementation of recent high-tech diagnostic tools such as multi-spectral analysis.