Studies on azulejo glaze welding by means of laser irradiation

Abstract

Azulejos (Portuguese glazed tiles) suffer from pathologies such as glaze fissures and glaze loss particularly as a result of exposure to wall moisture and weathering. Many tile panels need conservation measures, including the treatment of lacunae but there is currently a lack of efficient and long-lasting solutions. Lasers offer a number of unique advantages including for the study and conservation of cultural heritage. In the conservation/restoration field, up to now the attention of the scientific community has been focused mainly on the use of lasers for cleaning processes. In this communication the initial studies on a novel application of laser radiation for the controlled thermal fusion of a glaze are presented and its potential for the restoration of azulejos discussed. The influence of a CO2 laser processing parameters (focus distance, duration of the beam incidence, number of laser passes) have been tested in order to assess their effect on the test items. Tile replicas and authentic historic azulejo samples, of different glaze compositions and colours, have been irradiated. Optical and SEM microscopy have been used to study the morphological alterations and the impact on the laser irradiated glazes. Initial results are encouraging and further work towards the implementation of this methodology is in progress.