Laser cleaning of artificially soiled cotton fabric: Assessment of surface chemical effects

Abstract

The effectiveness of the cleaning methods to remove soiling and stains from fabric artefacts is often limited by their complex microscopic and macroscopic structures, including fibre bundles, warp, weft, narrow folds, sewing deformations, and others. These structures may sometimes make the complete fabric cleaning very challenging, and they can easily be damaged. To approach such a problem, the potential of pulsed laser treatments of artificially soiled cotton fabrics has been investigated. Laser tests were carried out on the following samples: (i) untreated cotton fabric, (ii) unaged-sized cotton fabric, and (iii) aged-sized cotton fabric with soiling. Moreover, vacuum cleaning was also considered prior to laser irradiations to evaluate whether standard treatments can favour a more effective laser cleaning treatment. The fundamental wavelength and second harmonics of a Q-Switched Nd:YAG laser (1,064,532 nm) were used for the experimentation. The morphology and chemical composition of the laser irradiated mock-ups were characterised through a multi-analytical approach, including Fibre Optic Reflectance Spectroscopy (FORS), colourimetry, optical microscopy, Diffuse reflectance-FTIR (DR-FTIR) spectroscopy, μ-Raman spectroscopy and X-ray fluorescence spectroscopy (XRF). Contrarily to what was reported in some literature, these analyses allowed to demonstrate the absence of any chemical change of the cellulose fibres and the possibility to optimise the laser parameters in order to achieve satisfactory and non-invasive laser cleaning results.