Investigations into the use of laser technology to reduce and remove dirt, debris, and accretions from the surface of 15th century wax votive images

Teresa Moreno

Abstract

This paper presents the results of a study that was carried out to investigate the use of laser technology in cleaning objects made of beeswax. Tests were conducted using a Q-switched Nd:YAG laser to reduce or remove dirt, debris and accretions from several small fragments of aged, brittle wax. In addition, observations were made on the effects that the heat emitted from the laser had on the wax substrate itself. The wax fragments that were tested are part of a rare collection of cast votive images (ex-votos) that were found in the Cathedral Church of St. Peter in Exeter in the mid 1940s. They date to the late 15th to early 16th century, and are of particular historical and religious significance. They were found behind the cresting of a screen high above the tomb of the venerated Bishop Edmund Lacey. They were placed there by medieval pilgrims who were either seeking miracles or offering thanks for miracles already performed. These wax fragments were preserved because they had remained hidden, while other such images were destroyed during the Reformation or simply melted down so the wax could be reused. After having been exposed to the elements in the cathedral for over four hundred years most of what survived consists only of small fragments. The wax itself is hard, dry and brittle, and all the fragments are covered with various types of dirt and debris. A range of analytical techniques were employed to characterize the wax and the surface deposits including gas chromatography-mass spectrometry (GC-MS), melting point, energy dispersive x-ray fluorescence (EDXRF), scanning electron microscopy (SEM), and optical microscopy. The results of these analyses, as well as the ethical concerns of treating religious artifacts will also be discussed.