Physical aspects of conservation

This thesis is concerned with comparing and contrasting different cleaning techniques of 3-D artifacts. Conventional cleaning techniques such as chemical, steam and mechanical have been applied on several objects at the Inorganics and Sculpture Conservation Division in the National Museums and Galleries on Merseyside in Liverpool. A Q-switched Nd:YAG laser system has also been developed for practical use in conservation and cleaning tests carries out on a variety of samples. The results have been recorded and compared with those obtained using conventional techniques. It was found that short laser pulses (~10ns) at 1064nm were the most adequate for the removal of black dirt layers from marble and limestone. The surface of the stone was not physically or chemically modified and the cleaning process was self-limiting, thus allowing the controlled removal of the aesthetically displeasing and structurally damaging crusts. Photographic evidence before and after treatment is also presented. Application of water before irradiation was found to improve the efficiency of dirt removal and a model concerning the involved physical mechanisms during laser cleaning has been proposed.