The use of an Er:YAG laser in the removal of biological growth from polychrome archaeological terracotta figurines from Cyprus

The British Museum preserves a large and archaeologically important collection of painted terracotta and limestone figurines from ancient Cyprus. These were the subject of a collaborative conservation and study programme as part of the Cyprus Digitisation Project. The figurines were covered by dark and ingrained speckles of biological growth, possibly linked to inappropriate storage conditions in the museum. These speckles significantly disfigured the appearance of the figurines and obscured physical features, manufacturing details, and surviving pigments. Traditional conservation treatment methods proved ineffective in reducing or removing the dark speckles on the terracottas, leading to the consideration of the use of an erbium yttrium aluminum garnet (Er:YAG) laser, since this technique proved successful in cleaning biological growth from the polychrome limestone figurines in the same collection. This study comprises the first known use of this technology on polychrome terracotta affected by biological growth. Highly satisfactory results were achieved, improving the understanding of archaeological aspects of the objects, while also pushing forward conservation science.