This study aims to compare the effects of some chemical agents on the removal of calcareous encrustations, which are characterized by the presence of both calcium and silicon. The experimentation was conducted during the conservation treatments of Cerriglio’s nymphaeum (Massa Lubrense, Naples, Italy). Tests were carried out in the laboratory on specimens and in situ to define the most efficient choice between several chelant agents, in the recovery of calcium and silicon, using ICP/OES and spectrocolorimetric and microscopic analyses.