Laser Cleaning of a Renaissance Epitaph with Traces of Azurite

Abstract

In Steyr, Austria, a Renaissance epitaph was cleaned by an Nd:YAG laser. Compared to cleaning tests, carried out with microsandblasting, (NH4)2CO3 and water compresses, the laser cleaning was much more sensible and faster. Satisfying results were realized for the calcareous sandstone of the frame as well as for the red and compact limestone of the relief. One of the big advantages was the detection of several traces of pigments, which were observed during the layered cleaning process. It can be assumed that other cleaning methods could not hold these last spots of polychrome surfaces. Care had to be taken of the energy. The application of higher energies on the red marble leads to colour changes into yellowish red.