Micro-Raman mapping on polished cross sections: a tool to define the penetration depth of conservation treatment on cultural heritage

Nowadays, in order to preserve the surfaces of works of art, several organic and inorganic substances are used. To evaluate the penetration depth and the distribution of these substances inside the materials, it is essential to define the effectiveness of a conservative treatment. Owing to the ambiguous results obtained with the current analytical techniques, the achievement of this aim is critical. This study shows how micro‐Raman mapping on polished cross section is an effective tool capable of investigating the inner portions of the materials. A set of painted plasters has been treated with ammonium oxalate solutions, an inorganic substance widely used for conservation works of carbonatic materials. The micro‐Raman mapping of the lines of the newly formed calcium oxalate allowed correlation of the penetration depth and the distribution of the product inside the specimens with different conditions of treatment. Moreover, a good agreement between micro‐Raman spectroscopy and microscopic techniques has been obtained. Copyright © 2010 John Wiley & Sons, Ltd. Evaluation of the penetration depth of consolidant products inside the porous matrix of stones or plasters is a hot issue in the conservation of works of art. This study shows how micro‐Raman mapping on polished cross section is an effective tool in evaluating the penetration depth and the distribution of consolidant products inside the matrix. A set of painted plasters was treated with ammonium oxalate, which is a widely used substance to preserve carbonatic materials, and the distribution of the newly formed calcium oxalate was assessed.