A new non invasive method to evaluate the detachments of plasters. First results

The conservation of the historical finishes represents a difficult issue, due to their aesthetical and functional roles. In particular, the investigation on surfaces (external o internal) with wall paintings represent a typical case where researchers has some difficulties to apply non invasive diagnostic technique about the detachment of these surfaces. The method here described is aimed at the definition of a scientific method for the evaluation of the adhesion between the fresco and the wall. To this end a proper measuring instrument, based essentially on the principle of stationary waves and suitable for easy use in situ, has been designed and realized. To better understand the range of reliability of the instrument and its limits, a set of measurements were carried out on a testing masonry. On this wall two layers of lime plaster were applied and different typologies of detachments were artificially created.