Er:YAG Laser Cleaning of Micromosaics from the Rosalinde and Arthur Gilbert Collection at the Victoria and Albert Museum

Conserving micromosaics from the Gilbert collection at the Victoria and Albert Museum is a challenge due to their complex structure and fragility. Their highly polished decorative surface prevents access to the substrate, yet deterioration can affect both, and manifests as cracking, failure and losses of the substrate and grouting, and as yellowing and accumulation of dirt on the uppermost organic coating. In order to minimise any possible damage to the substrate while cleaning the surface with solvents, laser cleaning using an Er:YAG laser was investigated on various micromosaic objects. Tests were first conducted on a non-displayable bonbonnière, and digital microscopy and scanning electron microscopy were performed to investigate the effects of the laser on the different materials; the results were then compared to solvent-cleaning only. The combination leading to the most effective cleaning results was found to be laser irradiation at fluences up to 0.71 J·cm−2 on the surface, followed by gentle swabbing with solvent. The surface was successfully cleaned with no changes induced on the materials, and a much lower amount of solvent was used. Following these successful preliminary tests, cleaning was undertaken on other pieces of the collection, and the outcome is presented in this study. The results show a great variability in terms of response of the materials to solvents, emphasising the need to consider each item on a case-by-case basis.