Feasibility of ultrafast picosecond laser cleaning of soiling on historical leather buckles

Abdelrazek Elnaggar,Yvette Fletcher,Paula Antunes,Anne Lama,Paul Fitzsimons,K G Watkins

doi:10.1186/s40494-016-0104-3

Abstract

The aim of the research is to present a system recently developed and used for automated cleaning of artworks and to examine the suitability of using this ultrafast and precise computed-scanning picosecond laser (1064 nm) with a repetition rate of 10 kHz and a temporal pulse length of 10 ps for the removal of soiling from leather buckles without damaging the leather substrate. Preliminary tests will be performed with the model artificially aged vegetable tanned samples to determine the leather damage threshold fluence and the soiling ablation threshold fluence before using a laser for the removal of the soiling from a historical leather buckle. As laser cleaning requires a physical parameterization for optimization of cleaning accompanied with an assessment of the morphological and chemical changes of leather, an investigations were performed to determine the leather damage and ablation threshold fluences of artificially aged and historical vegetable tanned leather using a number of analytical techniques including differential scanning calorimetry, optical microscopy, scanning electronic microscope with energy dispersive X-ray analysis, colorimetry and Fourier transform infrared spectroscopy have been used. Following optimization trials of the picosecond laser cleaning parameters on model leather samples, satisfactory removal of the soiling over the historical leather surface is achieved.

Highlights

While cleaning of sensitive organic objects, such as leather, should be accomplished with much care and well-assessed technical studies, the choice of a suitable cleaning method will need many basic tests to avoid damage and accept the minimal risk
Fourier transform infrared spectroscopy (FTIR) analysis of the soiling on the historical leather indicates the presence peaks ascribed to calcium carbonate at 878 and 1422 cm−1 and clay minerals at 795 and 1012 cm−1
The elemental analysis of the soiling on the buckles leathers using energy dispersive X-ray spectroscopy (EDS) analysis indicates the high presence of soot and dirt elements such as Carbon, Sulphur, Silica, Calcium, Chlorine, Aluminium, Sodium and Iron might be as a form of sodium aluminium silicates, gypsum and calcium carbonate

Summary

Introduction

While cleaning of sensitive organic objects, such as leather, should be accomplished with much care and well-assessed technical studies, the choice of a suitable cleaning method will need many basic tests to avoid damage and accept the minimal risk. Removal of soot and soiling from the leather surface is important for future restoration and consolidation treatments [1]. Several chemical and mechanical cleaning methods have been tested with leather to remove unwanted materials with high risk of leather damage [2, 3]. Laser cleaning is considered one of the least invasive studied cleaning techniques and it has been proved more beneficial in case of sensitive organic materials. Reports have indicated successful cleaning of soiling from collagen artefacts using nanosecond UV/

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Results

Conclusion