Tackling conservation challenges using erbium lasers: case studies at the British Museum

Research was conducted at the British Museum to investigate the potential of Er:YAG lasers to address challenging conservation problems where traditional conservation methods had failed. The approach followed was to perform laser tests on model samples and unregistered objects to determine the laser alteration threshold fluence on each substrate and the ability of the laser to remove contaminants, such as inorganic crusts and organic coatings. The effects of the laser were assessed by means of optical microscopy, scanning electron microscopy and colour measurements. If tests were successful on the samples and unregistered objects, the laser was then used on artefacts from the collection of the British Museum. This article details the successful results obtained using Er:YAG lasers for the removal of corrosion from metals, remains of old adhesives from ceramics and shells, mould from polychromed limestone and terracotta, modern overpainting and varnish from a fresco painting.