saving Surfaces finishes on terracotta tiles using laser cleaning

Examining the recent bibliographies on laser cleaning, there is evidence of a lack of applications on ceramic materials.1,2,3 Cleaning problems on architectural terracotta are not usually concerned with gypsum based black crusts which necessitate a calcareous substrate to grow. Nevertheless, black layers are very often evident on red terracotta elements exposed in outdoor environments, even when the material is purely silicatic.4 Moreover, terracotta easily pulverizes in presence of nitrates and sulphates and looses fragments. The damage due to soluble salts produces a poor mechanical strength in the decayed ceramic substrates and make troublesome the choice of the cleaning technique.